ANTI-CORROSION TREATMENT METHOD AND ANTI-CORROSION TREATED ARTICLE

Abstract

The present invention relates to: an anti-corrosion treatment method comprising the step of detecting an object comprising a metal or alloy and heating it to a temperature higher than 180°C or an object having, formed on its surface, a film or layer comprising a metal or alloy and heated to a temperature higher than 180°C with an aqueous solution containing an inorganic acid or an inorganic salt, or comprising the step of treating an object comprising a metal or alloy or an object having, formed on its surface, a film or layer comprising a metal or alloy with an aqueous solution containing at least one component selected from silicic acid, a salt of silicic acid, phosphoric acid, a salt of phosphoric acid, a monohydrogen phosphate salt, a dihydrogen phosphate salt and a zirconium salt;and an article characterized by being treated with anti-corrosion by the anti-corrosion treatment method.;

Description

ANTI-CORROSION TREATMENT METHOD AND ANTI-CORROSION TREATED ARTICLE FIELD OF INVENTION This description refers to an anti-corrosion method and an article treated with anti-corrosion. BACKGROUND OF THE INVENTION In conventional anti-corrosion methods, an anti-corrosion film or anti-corrosion layer containing a metal or alloy such as zinc is generally formed on a surface of metals or alloys. For example, Patent Document 1 describes an anti-corrosion coating composition, containing metal particles that have an inorganically based modification (specifically, silicon dioxide) on their surface (specifically, metal particles formed on the basis of zinc or zinc alloys), and a corrosion protection coating available from the anti-corrosion coating composition. Patent Document 2 describes a cured coating composition for corrosion inhibition or corrosion prevention for metallic substrates, the composition includes a resin binder and nanoparticles (specifically, ZnO, Al2O3, Al(O)OH or similar) of which the surface is treated with at least one surface group (specifically, polydialkylsiloxane or similar). Patent Document 3 describes a method for producing deformable corrosion protection capable on a metal surface. The method includes: a step for mixing metallic magnesium, zinc, aluminum, or titanium particles or mixtures or alloys containing at least one of these metals with at least one metal compound, wherein a reaction between the metal particles and the metal compound(s) results in modified metal particles on the surface; a step for applying the resulting modified metal particles on the surface to the metal surface; a step for hardening the produced layer of modified metal particles on the surface at temperatures between ambient temperature and 500°C; and a step for a tempering period carried out at temperatures ranging from 250°C to about 700°C and lasting from a few seconds to a few hours. [Previous Technique Document] [Patent Document] [Patent Document 1] Publication of Japanese Unexamined Patent Application No. 2018-70999 [Patent Document 2] Japanese Patent Application Open to the Public No. 20131 frfrenn / zznz / E / Yii 510932 [Patent Document 3] Japanese Patent Application Open to the Public No. 2012505963 BRIEF DESCRIPTION OF THE INVENTION [Problems to be Solved by the Invention] However, higher anti-corrosion performance is desirable, and it is also desirable to be able to easily impart good anti-corrosion performance. This description provides an anti-corrosion method capable of easily imparting improved anti-corrosion performance to metal or alloy materials. It also provides a product with enhanced anti-corrosion performance. [Means to Solve Problems] This description refers to the following points. [Point 1] An anti-corrosion method, which includes: a step for treating an object to be treated, which contains a metal or alloy or has on a surface a film or layer containing a metal or alloy, and has been heated to a temperature above 180°C, with an aqueous solution containing an inorganic acid or an inorganic salt. [Point 2] The anti-corrosion method according to point 1, wherein the object to be treated has a temperature above 220°C when treated with the aqueous solution. [Point 3] The anti-corrosion method according to point 1 or 2, wherein the aqueous solution containing an inorganic acid or inorganic salt is an aqueous solution containing at least one selected from silicic acid, silicate, phosphoric acid, phosphate, monohydrogen phosphate, dihydrogen phosphate, sulfuric acid, sulfate, nitric acid, nitrate, molybdenum acid, molybdate, and zirconium salt. [Point 4] The anti-corrosion method in accordance with any of points 1 to 3, wherein the aqueous solution contains 0.1% by mass or more of an inorganic acid and / or an inorganic salt. [Point 5] The anti-corrosion method in accordance with any of points 1 to 4, wherein the aqueous solution containing an inorganic acid or an inorganic salt also contains a lubricant. [Point 6] The anti-corrosion method in accordance with any of points 1 to 5, wherein the aqueous solution containing an inorganic acid or an inorganic salt has a pH of 4 or more. [Point 7] The anti-corrosion method in accordance with any of points 1 to 6 does not include: a step to heat the object to be treated to a temperature of 200°C or more after treating the object to be treated with the aqueous solution. [Item 8] An anti-corrosion method, comprising: a step for treating an object to be treated, which contains a metal or alloy or has on a surface a film or layer containing a metal or alloy, with an aqueous solution containing at least one selected from silicic acid, silicate, phosphoric acid, phosphate, monohydrogen phosphate, dihydrogen phosphate, and zirconium salt. [Point 9] The anti-corrosion method according to point 8, wherein the aqueous solution containing an inorganic acid or an inorganic salt also contains a lubricant. [Point 10] The anti-corrosion method according to point 8 or 9 does not include: a step to heat the object to be treated to a temperature of 200°C or more after treating the object to be treated with the aqueous solution. [Point 11] The anti-corrosion method in accordance with any of points 1 to 10, wherein the object to be treated contains at least one selected from zinc, zinc alloys, aluminum, aluminum alloys, iron, and iron alloys, or has on a surface a film or layer containing at least one selected from zinc, zinc alloys, aluminum, aluminum alloys, iron, and iron alloys. [Point 12] The anti-corrosion method according to any of points 1 to 10, wherein the object to be treated has on one surface an anti-corrosion film containing at least one selected from zinc, zinc alloys, aluminum, and aluminum alloys. [Point 13] An article to be treated with anti-corrosion by the anti-corrosion method in accordance with any of points 1 to 12. [Effects of the Invention] This description provides an anti-corrosion method capable of easily imparting improved corrosion resistance to metal or alloy materials. Furthermore, this description provides an article that offers improved corrosion resistance. BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1A is a photograph of a cold-rolled steel sheet that was subjected to immersion treatment with an aqueous sodium silicate solution from Example 58 after one hour from the start of a salt spray test. FIGURE 1B is a photograph of the cold-rolled steel sheet that was subjected to immersion treatment with the aqueous sodium silicate solution of Example 58 after five hours from the start of the salt spray test. FIGURE 2A is a photograph of a cold-rolled steel sheet that was not subjected to immersion treatment with an aqueous sodium silicate solution from Comparative Example 14 after one hour from the start of a salt spray test. FIGURE 2B is a photograph of the cold-rolled steel sheet that was not subjected to immersion treatment with the aqueous sodium silicate solution of Comparative Example 14 after five hours from the start of the salt spray test. i frfrenn / zznz / E / Yii DETAILED DESCRIPTION OF THE INVENTION [Methods for Carrying Out the Invention] An anti-corrosion method of a first embodiment of the description includes a step of treating an object to be treated, which contains a metal or alloy or has on its surface a film or layer containing a metal or alloy, and which has been heated to a temperature above 180°C, with an aqueous solution containing an inorganic acid or inorganic salt (hereafter also referred to as an “organic acid-based treatment agent”). An anti-corrosion method of a second embodiment of the description includes a step of treating an object to be treated, which contains a metal or alloy or has on its surface a film or layer containing a metal or alloy, with an aqueous solution containing at least one selected from silicic acid, silicate, phosphoric acid, phosphate, monohydrogen phosphate, dihydrogen phosphate, and zirconium salt.From now on, the anti-corrosion method of the first embodiment of the present description will also be collectively referred to as “the anti-corrosion method of the present description”. According to the anti-corrosion method described, an object to be treated, containing a metal or alloy, or having a film or layer containing a metal or alloy on its surface, is treated with an organic acid-based treatment agent. At this point, by adjusting the object to be treated to a temperature above 180°C, preferably above 220°C, when treated with the organic acid-based treatment agent, the anti-corrosion performance of the object to be treated can be improved. Among the organic acid-based treatment agents, when the object to be treated is treated with an aqueous solution containing at least one selected from silicic acid, silicate, phosphoric acid, phosphate, monohydrogen phosphate, dihydrogen phosphate, and zirconium salt, the anti-corrosion performance of the object to be treated can be efficiently improved if the object is at a temperature of 180°C or lower.In other words, according to the anti-corrosion method of the first embodiment, in which an object to be treated is heated to a temperature above 180°C and treated with the organic acid-based treatment agent, it is possible to readily impart improved anti-corrosion performance to metal or alloy materials. Furthermore, according to the anti-corrosion method of the second embodiment of the present description, in which an object to be treated is treated with an aqueous solution containing at least one selected from silicic acid, silicate, phosphoric acid, phosphate, monohydrogen phosphate, dihydrogen phosphate, and zirconium salt, it is possible to readily impart improved anti-corrosion performance to metal or alloy materials in any case where the object to be treated is heated to a temperature above 180°C, or is not heated to a temperature above 180°C and is, for example, at room temperature. ! bhrnn / 77n7 / E / Yl· The organic acid-based treatment agent used herein is an aqueous solution containing an inorganic acid and / or an inorganic salt. Examples of inorganic acids and inorganic salts include silicic acid, silicate, phosphoric acid, phosphate, monohydrogen phosphate, dihydrogen phosphate, sulfuric acid, sulfate, nitric acid, nitrate, molybdenum acid, molybdate, and zirconium salt. For silicic acid and silicate, any of orthosilicic acid and orthosilicate, pyrosilicic acid and pyrosilicate, metasilicic acid and metasilicate, or similar compounds may be used. For phosphoric acid and phosphate, any of orthophosphoric acid and orthophosphate, pyrophosphoric acid and pyrophosphate, metaphosphoric acid and metaphosphate, or similar compounds may be used. As inorganic acids and inorganic salts, preferred substances include silicic acid, silicate, phosphoric acid, phosphate, monohydrogen phosphate, dihydrogen phosphate, and zirconium salts. Silicate, phosphate, monohydrogen phosphate, dihydrogen phosphate, sulfate, nitrate, and molybdate, as inorganic salts, are preferably metal salts, specifically monovalent metal salts such as lithium salt, sodium salt, or potassium salt, or divalent metal salts such as magnesium salt or calcium salt. For example, zirconium carbonate, ammonium zirconium carbonate, potassium zirconium carbonate, and sodium zirconium carbonate are preferred as zirconium salts. As with inorganic acids and inorganic salts, one class of substance may be used alone, or two or more substances may be used in combination. The concentration of the organic acid-based treatment agent (an aqueous solution containing an inorganic acid or inorganic salt), i.e., the amount of inorganic acid and / or inorganic salt in the aqueous solution, is not specifically limited, but is usually preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more. Furthermore, the upper limit of the concentration of the organic acid-based treatment agent, i.e., the upper limit of the amount of inorganic acid and / or inorganic salt in the aqueous solution, is not specifically limited, and the aqueous solution may be saturated. However, it is usually preferably 15% by mass or less, and more preferably 5% by mass or less. The organic acid-based treatment agent may contain, within a range that does not match its desired effect, an additive or additive component such as a pH adjuster, water-soluble crosslinker, water-soluble resin, lubricant, pigment, defoamer, dispersant, anti-settlement agent, leveling agent, thickener, detarnisher, anti-scaling agent, antiseptic agent, UV absorber, dye, or similar. There are cases where it is preferable to add an additive or additive component such as a lubricant to the organic acid-based treatment agent to improve or change the physical properties of an item undergoing anti-corrosion treatment.On the other hand, when it is not necessary to change the physical properties of an article to be subjected to anti-corrosion treatment, it is usually preferable that the inorganic acid-based treatment agent not contain any additive component except for a pH adjuster. Furthermore, it is usually preferable that the organic acid-based treatment agent not contain any solvent other than water, i.e., not contain an organic solvent. However, in some cases, it is preferable to add an organic solvent in a small quantity (e.g., 10% by mass or less, preferably 5% by mass or less) from the standpoint of dispersibility or similar properties. According to one embodiment, the organic acid-based treatment agent used herein preferably contains a lubricant. By adding a lubricant to the organic acid-based treatment agent, it is possible to reduce the coefficient of friction on the surface of an article that has undergone an anti-corrosion treatment as described herein, and it is possible to easily control the coefficient of friction of a surface of an article that has undergone an anti-corrosion treatment as described herein. The lubricant is not particularly limited. Examples include polyolefins and modified polyolefins (polyethylene, modified polyethylene, polypropylene, modified polypropylene, etc.), waxes such as paraffin, carnava wax, fluororesins, melamine cyanurate, and hexagonal boron nitride. Waxes are usually added preferentially and mixed into an emulsion to prepare the organic acid-based treatment agent. Lubricants are commercially available. Examples of lubricants that can be used appropriately are CERAFLOUR 913 (product name), CERAFLOUR CERAFLOUR CERAFLOUR CERAFLOUR 914” (name 916” (name 925” (name 929” (product name), of product), of product), of product), CERAFLOUR CERAFLOUR CERAFLOUR CERAFLOUR 915” (name 917” (name 927” (name 950” (product name) of product) of product) of product) “CERAFLOUR 988” (product name), “CERAFLOUR 1000” (product name), “497” (product name), “AQUACER 507” (product name), “AQUACER 515” (product name), “AQUACER 526” (product name), “AQUACER 531” (product name), “AQUACER 537” (product name), “AQUACER 539” (product name), “AQUACER 552” (product name), “AQUACER 593” (product name), “AQUACER 840” (product name), “AQUACER 1547” (product name), “AQUAMAT 208” (product name), “AQUAMAT 263” (product name), “AQUAMAT 272” (product name), “AQUAMAT 8421” (product name), “HARDAMER PE02” (product name), “HARDAMER PE03” (product name), “HARDAMER PE04” (product name), “CERACOL 79” (product name), which are available from BYK Corporation; SANWAX 161-P (product name), SANWAX 131-P (product name), SANWAX 151-P (product name),SANWAX 171-P (product name), VISCOR 330-P (product name), VISCOR 440-P (product name), VISCOR 550-P (product name), VISCOR 660-P (product name), which are available from Sanyo Chemical Industries, Ltd.; “Hi-WAX 100P” (product name), “Hi-WAX 400P” (product name), “Hi-WAX 800P” (product name), “Hi-WAX 1105A” (product name), “Hi-WAX 2203A” (product name), “Hi-WAX 1120H” (product name), “Hi-WAX 4202E” (product name), “Hi-WAX 405MP” (product name), “Hi-WAX 4051E” (product name), “Hi-WAX 410P” (product name), which are available from Mitsui Chemicals, Inc.; LICOWAX PE 520 (product name), “LICOWAX PE 130” (product name), “LICOWAX PE 190” (product name), “LICOWAX PED 521” (product name), “LICOWAX PED 522” (product name), “LICOWAX PED 153” (product name), “LICOWAX PED 191” (product name), “LICOWAX PED 192” (product name), “LICOWAX 371 FP” (product name),“LYCOCENE “PP 6102” (product name), “LYCOCENE PP 6502” (product name), “LYCOCENE PP 7502” (product name), “LYCOCENE PP 1302” (product name), “LYCOCENE PP 1502” (product name), “LYCOCENE PP 1602” (product name), “LYCOCENE PP 2602” (product name), “LYCOCENE PP 3602” (product name), “LYCOCENE PE 4201” (product name), “LYCOCENE PE 5301” (product name), “LYCOCENE PP MA 1332” (product name), “LYCOCENE PP MA 6252” (product name), “LYCOCENE PP MA 6452” (product name), “LYCOCENE PP MA 7452” (product name), “LYCOCENE PE MA 4221” (product name), “LICOCENE PE MA 4351” “CERIDUST 3620” (product name), “CERIDUST3610” (product name), “CERIDUST 3715” (product name), “CERIDUST 6050 M” (product name), “CERIDUST 9610 F” (product name), “CERIDUST 9630 F” (product name), “CERIDUST 3920 F” (product name), “CERIDUST 3940 F” (product name),“CERIDUST 9202 F” (product name), “CERIDUST 9205 F” (product name), which are available from Clariant; “Epolene E-10” (product name), “Epolene E-10P” (product name), “Epolene E-14” (product name), “Epolene E-14E” (product name), “Epolene E-14EP” (product name), “Epolene E-14P” (product name), “Epolene E-16” (product name), “Epolene E-20” (product name), “Epolene E-20P” (product name), “Epolene EE-2” (product name), “Epolene E-43” (product name), “Epolene E-43P” (product name), which are available from Westlake; “Hi-Disper A-113” (product name), “Hi-Disper A-375” (product name), “Hi-Disper AB-50” (product name), “Hi-Disper AF-41” (product name), “Hi-Disper AQ-73” (product name), “Hi-Disper A-110” (product name), “Hi-Disper A-512” (product name), “Hi-Disper A-348” (product name), “Hi-Disper A-332” (product name), “Hi-Disper A-206N” (product name),“Hi-Disper AD-62” (product name), which are available from Gifu Shellac Manufacturing Co.,Ltd.;, i frfrenn / zznz / E / Yii “nanoFLONE PTFE AQ 60” (product name), “nanoFLONE PTFE AQ 50 SM” (product name), which are available from Shamrock Technologies, Inc.; “Poligen WE 1” (product name), “Poligen WE 3” (product name), “Poligen WE 4” (product name), “Poligen WE 6” (product name), “Poligen Wax V Flakes” (product name), which are available from BASF; and “LUBRON LDW-410” (product name), which are available from DAIKIN INDUSTRIES, LTD. As a lubricant, one class of substance may be used alone, or two or more substances may be used in combination. The amount of lubricant in the organic acid-based treatment agent (an aqueous solution containing an inorganic acid or an inorganic salt) is not particularly limited and may be appropriately selected to obtain a desired coefficient of friction of an article's surface, but is usually preferably 10% by mass or less. Incidentally, the organic acid-based treatment agent used in the present description can be prepared by mixing and dissolving a predetermined amount of an inorganic acid and / or an inorganic salt, as well as an additive or additive component if necessary, in a water solvent by a known method. According to one embodiment, the pH of the organic acid-based treatment agent (an aqueous solution containing an inorganic acid or inorganic salt) used herein is preferably 4 or higher, more preferably 4 to 12. If the pH is less than 4, a surface containing a metal or alloy may be susceptible to the acid. Furthermore, as the pH increases, care may need to be taken in handling for safety reasons. Note that the pH in herein refers to the pH at 20°C. In the present description, since the pH of the organic acid-based treatment agent varies depending on the type and concentration of the inorganic acid and inorganic salt used, sodium hydroxide, potassium hydroxide, lithium hydroxide, nitric acid, or similar may be used as a pH adjuster for the purpose of adjusting the pH to a predetermined value. The object to be treated, to which the anti-corrosion method described herein applies, has a metallic or alloy material on its surface. Specifically, the object to be treated contains a metal or alloy, or has a film or layer containing a metal or alloy on its surface. The film or layer containing a metal or alloy may be present over the entire surface of the object to be treated or may only be formed on a portion of the surface. The metal or alloy materials to which the anti-corrosion method described herein may be applied are not specifically limited. Examples include zinc and zinc alloys such as Zn-Al alloys; aluminum and aluminum alloys such as Al-Mg alloys; iron and iron alloys such as carbon steel; and magnesium alloys such as Mg-Zn alloys. Among them, when an object to be treated contains at least one selected zinc, zinc alloys, aluminum, aluminum alloys, iron, or iron alloys, or has on its surface a film or layer containing at least one selected zinc, zinc alloys, aluminum, aluminum alloys, iron, or iron alloys, the anti-corrosion method described herein can be appropriately applied to that object. In this case, the zinc alloys (or aluminum alloys) may be a zinc-aluminum alloy. As an anti-corrosion treatment for a metal or alloy material, an anti-corrosion film containing zinc, a zinc alloy, aluminum, or an aluminum alloy is generally formed on its surface.Also, in the case where an object to be treated has on its surface this anti-corrosion film containing at least one selected zinc, zinc alloys, aluminum, and aluminum alloys, the anti-corrosion method of the description can be appropriately stacked on that object to be treated to further improve the anti-corrosion performance. According to the anti-corrosion method described, an object to be treated, which contains a metal or alloy or has a film or layer containing a metal or alloy on its surface, is preferably heated to a temperature above 180°C or left unheated, and is treated with the organic acid-based treatment agent described above (an aqueous solution containing an inorganic acid or inorganic salt). The organic acid-based treatment agent may also be heated or left unheated, or it may be cooled to a point where it does not solidify. Treatment with the organic acid-based treatment agent can be carried out, for example, by immersion treatment, in which the object to be treated is immersed in the organic acid-based treatment agent, or by spray treatment, in which the organic acid-based treatment agent is sprayed onto the object to be treated.According to the corrosion protection method of the first embodiment of the present description, an object to be treated has a temperature above 180°C, preferably above 220°C, when treated with the organic acid-based treatment agent. According to the corrosion protection method of the second embodiment of the present description, the temperature of an object to be treated when the object is treated with the organic acid-based treatment agent (an aqueous solution containing at least one selected from silicic acid, silicate, phosphoric acid, phosphate, monohydrogen phosphate, dihydrogen phosphate, and zirconium salt) is not particularly limited and may be 180°C or lower.However, an object to be treated preferably has a temperature above 180°C, and more preferably above 220°C when treated with the organic acid-based treatment agent, in order to further improve its anti-corrosion performance. Incidentally, depending on the type of lubricant added, the coefficient of friction of an article's surface may decrease when the object to be treated has a high temperature, for example, when it exceeds 180°C or higher. According to the anti-corrosion method of both the first and second embodiments, the upper limit value of the temperature of an object to be treated when the object is treated with the organic acid-based treatment agent is not particularly limited, but is usually preferably 350°C or less, more preferably 320°C or less. Furthermore, the temperature of the organic acid-based treatment agent used in treating an object to be treated is not particularly limited, and may be below the boiling point and above the freezing point of the organic acid-based treatment agent (an aqueous solution containing an inorganic acid or an inorganic salt), but is usually preferably around 15 to 50°C from the point of view of cost and ease of operation. The treatment time of an object to be treated with the organic acid-based treatment agent (an aqueous solution containing an inorganic acid or inorganic salt) (in the case of immersion treatment, the time for immersing the object to be treated in the organic acid-based treatment agent; and in the case of spray treatment, the time for spraying the organic acid-based treatment agent onto the object to be treated) is not specifically limited because it may depend on the concentration of the organic acid-based treatment agent or similar. However, it is usually preferably 1 second or more, and more preferably 5 seconds or more.On the other hand, an object to be treated can be treated with the organic acid-based treatment agent for a prolonged time, but from the point of view of productivity and efficiency, it is usually preferably 15 minutes or less, more preferably 10 minutes or less. Note that treatment with the organic acid-based treatment agent does not necessarily have to be carried out on all surfaces of an object to be treated, but it can preferably be carried out on the entire surface or at least on a portion of the surface containing a metal or alloy. For example, in the case of immersion treatment, the entire object to be treated can be immersed in the organic acid-based treatment agent, or only the surface containing a metal or alloy of the object can be immersed in the organic acid-based treatment agent. In the case of spray treatment, the organic acid-based treatment agent can be sprayed on all surfaces, including a surface that does not contain a metal or alloy, but the organic acid-based treatment agent is necessarily only sprayed on the surface containing a metal or alloy. Note that treatment with the organic acid-based treatment agent can be carried out on the entire surface simultaneously or on each surface sequentially. Furthermore, all surfaces of an object to be treated can be treated with the same organic acid-based treatment agent (an aqueous solution containing an inorganic acid or an inorganic salt), or they can be treated with different ones. The heating of the object to be treated and the heating or cooling of the organic acid-based treatment agent can be carried out by known means. The treatment with the organic acid-based treatment agent, specifically immersion and spray treatments, can also be carried out by known means. Furthermore, the treatment conditions, except for the temperature of the object to be treated, the temperature of the organic acid-based treatment agent, and the treatment time, are not particularly limited and can be selected appropriately. In both immersion and spray treatments, it is preferred that the entire surface containing a metal or alloy be treated uniformly. After an object to be treated is treated with the organic acid-based treatment agent (an aqueous solution containing an inorganic acid or an inorganic salt), the object can be subjected to washing with water or similar as required and dried, thereby obtaining an article that has undergone the anti-corrosion treatment of the present description. The drying of an object treated with an organic acid-based treatment agent can be carried out by known means, and the drying conditions are not particularly limited and can be selected appropriately. For example, drying can be done naturally, with air at ordinary temperature, or by centrifugal drying. Drying can be carried out in an atmosphere, in an inert gas such as nitrogen gas, or under reduced pressure. Although the object to be treated can be heated and dried, only the removal of the water solvent is required, and heating the object to a high temperature is not necessary in this description. From a cost and ease of operation standpoint, it is usually preferable not to heat the object to a high temperature. Specifically, it is preferable not to include a step to heat the object to 200°C or higher after treating it with the organic acid-based treatment agent. It is even more preferable not to include a step to heat the object to 150°C or higher. According to one embodiment, an object to be treated, to which the anti-corrosion method described herein is applied, has on its surface a film or layer containing a metal or alloy, such as an anti-corrosion film containing zinc, a zinc alloy, aluminum, or an aluminum alloy. This film or layer containing a metal such as zinc, aluminum, or alloys thereof can be formed by a known method. For example, it can be formed by applying a solution or dispersion liquid containing metal or alloy particles and a binding resin or a precursor thereof (a monomer or oligomer that polymerizes or cures into a binding resin) to a surface of the object to be treated, then heating it to a high temperature to remove the solvent, and, in the case of a binding resin precursor, polymerizing or curing it.The heating temperature to form a film or layer containing a material or alloy is frequently above 250°C or may be above 300°C. In the case of an object to be treated that has on a surface a film or layer containing a metal or alloy, after an article, which is an object to be treated, is heated to a temperature above 250°C or even to a temperature above 300°C to form a film or layer containing a metal or alloy on a surface as described above, the object to be treated may be treated with the organic acid-based treatment agent (an aqueous solution containing an inorganic acid or an inorganic salt) in a state where the object is not cooled so that it has a temperature above 250°C or the object is cooled slightly naturally such that it has a temperature above 180°C.Implementing the anti-corrosion treatment described herein in this manner is preferable because it eliminates the need to cool and reheat an object to be treated after forming a film or layer containing a metal or alloy on a surface, thus shortening the process. Note that there is no particular limitation on a method for forming an anti-corrosion film containing zinc, a zinc alloy, aluminum, or an aluminum alloy on a surface of an article to be treated. For example, the anti-corrosion film can be adequately formed by methods described in Japanese Patent Open to the Public No. 2005-200678 and Japanese Patent Open to the Public No. 2006-52361. Examples From now on, the present description will be described in more detail by means of examples, but it is not limited to mime. <Ejemplo 1> By uniformly mixing the following components, a base coating treatment agent containing zinc flakes as a main component was prepared. Deionized water: 39.06% by mass i frfrenn / zznz / E / Yii Zinc flakes: 32.12% by mass Aluminum flakes: 5.08% by mass DPG (dipropylene glycol): 10.29% by mass Synperonic (registered trademark) 13 / 6.5:3.15% by mass Silquest (registered trademark) A187: 8.66% by mass Schwego foam (registered trademark): 0.40% by mass Ñipar (registered trademark) S10: 0.71% by mass Aerosol (registered trademark) TR70: 0.53% by mass The components listed above under the product names are as follows. Synperonic (registered trademark) 13 / 6.5: polyoxyethylene (6.5) surfactant Silquest (registered trademark) A187: y-glycidoxypropyltrimethoxysilane Schwego foam (registered trademark): defoamer Ñipar (registered trademark) S10:1-nitropropane Aerosol (registered trademark) TR70: anionic surfactant (bistridecyl sodium sulfosuccinate) Additionally, as a dip treatment agent, sodium silicate was dissolved in deionized water to prepare 150 mL of an aqueous solution containing 3% by mass of sodium silicate. The pH of the prepared dip treatment agent was 11.4. Next, five M6 hex flange bolts, which had been steam degreased with dichloromethane and shot blasted, were coated with the base coating treatment agent by an immersion method involving centrifugal agitation (an immersion centrifuge method), preheated to 100°C for 10 minutes in an electric oven, and baked at 330°C for 30 minutes in an electric oven to form a zinc-aluminum coating. The coating deposition rate was 6 g / m². From now on, this process for forming a zinc-aluminum coating will be referred to as the “base treatment.” It was then confirmed that the surface temperature of five bolts removed from the electric furnace was between 265°C and 300°C using an infrared thermometer. The bolts were immersed in 150 mL of an aqueous solution containing 3% by mass of sodium silicate at a solution temperature of 20°C for approximately 10 seconds. The bolts were then removed and dried to prepare five bolts that had undergone both the base treatment and the immersion treatment. The five bolts prepared in this way, which had been subjected to the base treatment (coating deposition amount: 6 g / m2) and the immersion treatment (aqueous sodium silicate solution; surface temperature of the bolts: 265°C to 300°C), were then subjected to a salt spray test in accordance with JIS Z-2371. i frfrenn / zznz / E / Yi The bolts were checked for rust every 168 hours from the start of the test to assess corrosion resistance. As a result, rust formation was not confirmed for any of the five bolts at 840 hours from the start of the salt spray test, and rust formation was confirmed for only one bolt at 1008 hours from the start of the test.<Ejemplo Comparativo 1> Five bolts that had been subjected only to the base treatment were prepared the same as in Example 1, except that after the base treatment, the immersion treatment with the aqueous solution containing 3% by mass of sodium silicate was not carried out and the bolts were cooled to room temperature as they were. The five bolts prepared in this manner, which had only undergone the base treatment (coating deposition rate: 6 g / m²), were then subjected to a salt spray test according to JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was confirmed on two of the five bolts 168 hours after the start of the salt spray test. At 336 hours after the start of the test, rust formation was confirmed on three or more bolts, which was more than half of the five bolts. <Ejemplo 2> Five bolts that had undergone the base treatment and the immersion treatment were prepared the same as in Example 1, except that the rotational frequency of the centrifugal stirring in the centrifugation method in the base treatment was changed to change the amount of coating deposition containing zinc and aluminum to 8 g / m2. The five bolts prepared in this manner, which had undergone the base treatment (coating deposition rate: 8 g / m²) and the immersion treatment (aqueous sodium silicate solution; bolt surface temperature: 265°C to 300°C), were then subjected to a salt spray test in accordance with JIS Z-2371, in the same manner as Example 1, to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts 1008 hours after the start of the salt spray test. <Ejemplo Comparativo 2> Five bolts that had been subjected only to the base treatment were prepared the same as in Example 2, except that after the base treatment, the immersion treatment with the aqueous solution containing 3% by mass of sodium silicate was not carried out and the bolts were cooled to room temperature as they were. The five bolts prepared in this way, which had only undergone the base treatment (coating deposition amount: 8 g / m2), were then subjected to a salt spray test in accordance with JIS Z-2371 in the same way as i frfrenn / zznz / E / Yii Example 1 for evaluating corrosion resistance. As a result, rust formation was confirmed on two of the five bolts 168 hours after the start of the salt spray test. At 336 hours after the start of the test, rust formation was confirmed on three or more bolts, which was more than half of the five bolts.

[0058] <Ejemplo 3> Five bolts that had undergone the base treatment and the immersion treatment were prepared the same as in Example 1, except that the rotational frequency of the centrifugal stirring in the centrifugation method in the base treatment was changed to change the amount of coating deposition containing zinc and aluminum to 10 g / m2. The five bolts prepared in this manner, which had undergone the base treatment (coating deposition rate: 10 g / m²) and the immersion treatment (aqueous sodium silicate solution; bolt surface temperature: 265°C to 300°C), were then subjected to a salt spray test in accordance with JIS Z-2371, in the same manner as Example 1, to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts 1008 hours after the start of the salt spray test. <Ejemplo Comparativo 3> Five bolts that had been subjected only to the base treatment were prepared the same as in Example 3, except that after the base treatment, the immersion treatment with the aqueous solution containing 3% by mass of sodium silicate was not carried out and the bolts were cooled to room temperature as they were. The five bolts prepared in this manner, which had only undergone the base treatment (coating deposition rate: 10 g / m²), were then subjected to a salt spray test in accordance with JIS Z-2371, in the same manner as Example 1, to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts at 168 hours from the start of the salt spray test, but rust formation was confirmed in three or more bolts, which was more than half of the five bolts, at 336 hours from the start of the test. <Ejemplo 4> Five bolts that had undergone the base treatment and the immersion treatment were prepared the same as in Example 1, except that the rotational frequency of the centrifugal stirring in the centrifugation method in the base treatment was changed to change the amount of coating deposition containing zinc and aluminum to 12 g / m2. The five bolts prepared in this manner, which had undergone the i frfrenn / zznz / E / Yii base treatment (coating deposition rate: 12 g / m²) and the immersion treatment (aqueous sodium silicate solution; bolt surface temperature: 265°C to 300°C), were then subjected to a salt spray test in accordance with JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for any of the five bolts at 1008 hours from the start of the salt spray test. At 1176 hours from the start of the test, rust formation was not confirmed for any of the five bolts. Rust formation was confirmed on only one bolt at 1344 hours from the start of the test. At 2016 hours from the start of the test, rust formation was confirmed on only one bolt. <Ejemplo Comparativo 4> Five bolts that had been subjected only to the base treatment were prepared the same as in Example 4, except that after the base treatment, the immersion treatment with the aqueous solution containing 3% by mass of sodium silicate was not carried out and the bolts were cooled to room temperature as they were.

[0065] The five bolts prepared in this manner, which had only undergone the base treatment (coating deposition rate: 12 g / m²), were then subjected to a salt spray test in accordance with JIS Z-2371, in the same manner as Example 1, to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts at 168 hours from the start of the salt spray test, but rust formation was confirmed in two bolts at 336 hours from the start of the test. At 504 hours from the start of the test, rust formation was confirmed in three or more bolts, which was more than half of the five bolts. <Ejemplo 5> As a dip treatment agent, sodium silicate was dissolved in deionized water to prepare 150 mL of an aqueous solution containing 0.1% by mass of sodium silicate. The pH of the prepared dip treatment agent was 10.2. Five bolts that had undergone both the base treatment and the dip treatment were prepared in the same manner as in Example 4, except that the dip treatment was carried out using the 150 mL of the aqueous solution containing 0.1% by mass of sodium silicate at a solution temperature of 20°C instead of the 150 mL of aqueous solution containing 3% by mass of sodium silicate at a solution temperature of 20°C. The five bolts prepared in this manner, which had undergone the base treatment (coating deposition rate: 12 g / m²) and the immersion treatment (aqueous solution containing 0.1% by mass of sodium silicate; bolt surface temperature: 265°C to 300°C), were then subjected to a salt spray test in accordance with JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts at 840 hours from the start of the salt spray test. <Ejemplo 6> As a dip treatment agent, sodium silicate was dissolved in deionized water to prepare 150 mL of an aqueous solution containing 0.3% by mass of sodium silicate. The pH of the prepared dip treatment agent was 10.3. Five bolts that had undergone both the base treatment and the dip treatment were prepared in the same manner as in Example 4, except that the dip treatment was carried out using the 150 mL of the aqueous solution containing 0.3% by mass of sodium silicate at a solution temperature of 20°C instead of the 150 mL of aqueous solution containing 3% by mass of sodium silicate at a solution temperature of 20°C. The five bolts prepared in this manner, which had undergone the base treatment (coating deposition rate: 12 g / m²) and the immersion treatment (aqueous solution containing 0.3% by mass of sodium silicate; bolt surface temperature: 265°C to 300°C), were then subjected to a salt spray test in accordance with JIS Z-2371, in the same manner as Example 1, to evaluate corrosion resistance. As a result, rust formation was not confirmed for any of the five bolts at 840 hours from the start of the salt spray test. At 1008 hours from the start of the test, rust formation was confirmed in one bolt. Also, at 1344 hours from the start of the test, rust formation was confirmed in only one bolt. <Ejemplo 7> As a dip treatment agent, sodium silicate was dissolved in deionized water to prepare 150 mL of an aqueous solution containing 0.5% by mass of sodium silicate. The pH of the prepared dip treatment agent was 10.9. Five bolts that had undergone both the base treatment and the dip treatment were prepared in the same manner as in Example 4, except that the dip treatment was carried out using the 150 mL of the aqueous solution containing 0.5% by mass of sodium silicate at a solution temperature of 20°C instead of the 150 mL of aqueous solution containing 3% by mass of sodium silicate at a solution temperature of 20°C. The five bolts prepared in this manner, which had undergone the base treatment (coating deposition rate: 12 g / m²) and the immersion treatment (aqueous solution containing 0.5% by mass of sodium silicate; bolt surface temperature: 265°C to 300°C), were then subjected to a salt spray test in accordance with JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for any of the five bolts at 1680 hours from the start of the salt spray test. At 1848 hours from the start of the test, rust formation was confirmed in one bolt. Also, at 2016 hours from the start of the test, rust formation was confirmed in only one bolt.<Ejemplo 8> As a dip treatment agent, sodium silicate was dissolved in deionized water to prepare 150 mL of an aqueous solution containing 1% by mass of sodium silicate. The pH of the prepared dip treatment agent was 11.1. Five bolts that had undergone both the base treatment and the dip treatment were prepared in the same manner as in Example 4, except that the dip treatment was carried out using 150 mL of the aqueous solution containing 1% by mass of sodium silicate at a solution temperature of 20°C instead of 150 mL of the aqueous solution containing 3% by mass of sodium silicate at a solution temperature of 20°C. The five bolts prepared in this manner, which had undergone the base treatment (coating deposition rate: 12 g / m²) and the immersion treatment (aqueous solution containing 1% by mass of sodium silicate; bolt surface temperature: 265°C to 300°C), were then subjected to a salt spray test in accordance with JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts 2148 hours after the start of the salt spray test. <Ejemplo 9> As a dip treatment agent, sodium silicate was dissolved in deionized water to prepare 150 mL of an aqueous solution containing 5% by mass of sodium silicate. The pH of the prepared dip treatment agent was 11.5. Five bolts that had undergone both the base treatment and the dip treatment were prepared in the same manner as in Example 4, except that the dip treatment was carried out using 150 mL of the aqueous solution containing 5% by mass of sodium silicate at a solution temperature of 20°C instead of 150 mL of the aqueous solution containing 3% by mass of sodium silicate at a solution temperature of 20°C. The five bolts prepared in this manner, which had undergone the base treatment (coating deposition rate: 12 g / m²) and the immersion treatment (aqueous solution containing 5% by mass of sodium silicate; bolt surface temperature: 265°C to 300°C), were then subjected to a salt spray test in accordance with JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts 1176 hours after the start of the salt spray test. <Ejemplo 10> As a dip treatment agent, sodium silicate was dissolved in deionized water to prepare 150 mL of an aqueous solution containing 10% by mass of sodium silicate. The pH of the prepared dip treatment agent was 11.6. Five bolts that had undergone the base treatment and the dip treatment were prepared in the same way as in Example 4, except that the dip treatment was carried out using 150 mL of the aqueous solution containing 10% by mass of sodium silicate at a solution temperature of 20°C instead of 150 mL of the aqueous solution containing 3% by mass of sodium silicate at a solution temperature of 20°C. The five bolts prepared in this manner, which had undergone the base treatment (coating deposition rate: 12 g / m²) and the immersion treatment (aqueous solution containing 10% sodium silicate by mass; bolt surface temperature: 265°C to 300°C), were then subjected to a salt spray test according to JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for any of the five bolts at 1680 hours from the start of the salt spray test. At 1848 hours from the start of the test, rust formation was confirmed in one bolt. Also, at 2016 hours from the start of the test, rust formation was confirmed in only one bolt. <Ejemplo 11> As a dip treatment agent, sodium silicate was dissolved in deionized water to prepare 150 mL of an aqueous solution containing 15% by mass of sodium silicate. The pH of the prepared dip treatment agent was 11.6. Five bolts that had undergone both the base treatment and the dip treatment were prepared in the same manner as in Example 4, except that the dip treatment was carried out using the 150 mL of the aqueous solution containing 15% by mass of sodium silicate at a solution temperature of 20°C instead of the 150 mL of aqueous solution containing 3% by mass of sodium silicate at a solution temperature of 20°C. The five bolts prepared in this manner, which had undergone the base treatment (coating deposition rate: 12 g / m²) and the immersion treatment (aqueous solution containing 15% sodium silicate by mass; bolt surface temperature: 265°C to 300°C), were then subjected to a salt spray test according to JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for any of the five bolts at 1680 hours from the start of the salt spray test. At 1848 hours from the start of the test, rust formation was confirmed in one bolt. Also, at 2016 hours from the start of the test, rust formation was confirmed in only one bolt. <Ejemplo 12> As a dip treatment agent, sodium dihydrogen phosphate was dissolved in deionized water to prepare 150 mL of an aqueous solution containing 5% by mass of sodium dihydrogen phosphate. The pH of the prepared dip treatment agent was 4.3. Five bolts that had undergone the base treatment and the dip treatment were prepared in the same way as in Example 4, except that the dip treatment was carried out using 150 mL of the aqueous solution containing 5% by mass of sodium dihydrogen phosphate at a solution temperature of 20°C instead of 150 mL of the aqueous solution containing 3% by mass of sodium silicate at a solution temperature of 20°C. The five bolts prepared in this manner, which had undergone the base treatment (coating deposition rate: 12 g / m²) and the immersion treatment (aqueous sodium diacid phosphate solution; bolt surface temperature: 265°C to 300°C), were then subjected to a salt spray test in accordance with JIS Z-2371, in the same manner as Example 1, to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts 1008 hours after the start of the salt spray test. <Ejemplo 13> As a dip treatment agent, ammonium zirconium carbonate (“Bacote 20” [product name] available from Nippon Light Metal Company, Ltd.) was dissolved in deionized water to prepare 150 mL of an aqueous solution containing 5% by mass of ammonium zirconium carbonate. The pH of the prepared dip treatment agent was 9.2. Five bolts that had undergone both the base treatment and the dip treatment were prepared in the same manner as in Example 4, except that the dip treatment was carried out using the 150 mL of the aqueous solution containing 5% by mass of ammonium zirconium carbonate at a solution temperature of 20°C instead of the 150 mL of aqueous solution containing 3% by mass of sodium silicate at a solution temperature of 20°C. The five bolts prepared in this manner, which had undergone the base treatment (coating deposition rate: 12 g / m²) and the immersion treatment (aqueous ammonium zirconium carbonate solution; bolt surface temperature: 265°C to 300°C), were then subjected to a salt spray test in accordance with JIS Z-2371, in the same manner as Example 1, to evaluate corrosion resistance. As a result, rust formation was not confirmed for any of the five bolts at 1008 hours from the start of the salt spray test, and rust formation was confirmed on only one bolt at 1176 hours from the start of the test. <Ejemplo 14> As a dip treatment agent, sodium nitrate was dissolved in deionized water to prepare 150 mL of an aqueous solution containing 5% by mass of sodium nitrate. The pH of the prepared dip treatment agent was 6.8. Five bolts that had undergone both the base treatment and the dip treatment were prepared in the same manner as in Example 4, except that the dip treatment was carried out using 150 mL of the aqueous solution containing 5% by mass of sodium nitrate at a solution temperature of 20°C instead of 150 mL of the aqueous solution containing 3% by mass of sodium silicate at a solution temperature of 20°C. The five bolts prepared in this manner, which had undergone the base treatment (coating deposition rate: 12 g / m²) and the immersion treatment (aqueous sodium nitrate solution; bolt surface temperature: 265°C to 300°C), were then subjected to a salt spray test in accordance with JIS Z-2371, in the same manner as Example 1, to evaluate corrosion resistance. As a result, rust formation was not confirmed for any of the five bolts at 504 hours from the start of the salt spray test, and rust formation was confirmed in only one bolt at 672 hours from the start of the test. <Ejemplo 15> As a dip treatment agent, potassium sulfate was dissolved in deionized water to prepare 150 mL of an aqueous solution containing 5% by mass of potassium sulfate. The pH of the prepared dip treatment agent was 5.8. Five bolts that had undergone both the base treatment and the dip treatment were prepared in the same manner as in Example 4, except that the dip treatment was carried out using 150 mL of the aqueous solution containing 5% by mass of potassium sulfate at a solution temperature of 20°C instead of 150 mL of the aqueous solution containing 3% by mass of sodium silicate at a solution temperature of 20°C. The five bolts prepared in this manner, which had undergone the base treatment (coating deposition rate: 12 g / m²) and the immersion treatment (aqueous potassium sulfate solution; bolt surface temperature: 265°C to 300°C), were then subjected to a salt spray test in accordance with JIS Z-2371, in the same manner as Example 1, to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts 504 hours after the start of the salt spray test. <Ejemplo 16> As a dip treatment agent, potassium molybdate was dissolved in deionized water to prepare 150 mL of an aqueous solution containing 5% by mass of sodium molybdate. The pH of the prepared dip treatment agent was 8.1. Five bolts that had undergone both the base treatment and the dip treatment were prepared in the same manner as in Example 4, except that the dip treatment was carried out using the 150 mL of the aqueous solution containing 5% by mass of sodium molybdate at a solution temperature of 20°C instead of the 150 mL of aqueous solution containing 3% by mass of sodium silicate at a solution temperature of 20°C. The five bolts prepared in this manner, which had undergone the i frfrenn / zznz / E / Yii base treatment (coating deposition rate: 12 g / m²) and the immersion treatment (aqueous sodium molybdate solution; bolt surface temperature: 265°C to 300°C), were then subjected to a salt spray test in accordance with JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts at 336 hours from the start of the salt spray test, and rust formation was confirmed on only one bolt at 504 hours from the start of the test. <Ejemplo Comparativo 5> As a dip treatment agent, a silane coupling agent (“A187T” available from Momentive Performance Materials Japan Co., Ltd.) was dissolved in deionized water to prepare 150 mL of an aqueous solution containing 5% by mass of the silane coupling agent. Five bolts that had undergone the base treatment and the dip treatment were prepared in the same way as in Example 4, except that the dip treatment was carried out using the 150 mL of the aqueous solution containing 5% by mass of the silane coupling agent at a solution temperature of 20°C instead of 150 mL of the aqueous solution containing 3% by mass of sodium silicate at a solution temperature of 20°C. The five bolts prepared in this manner, which had undergone the base treatment (coating deposition rate: 12 g / m²) and the immersion treatment (aqueous solution of silane coupling agent; bolt surface temperature: 265°C to 300°C), were then subjected to a salt spray test in accordance with JIS Z-2371, in the same manner as Example 1, to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts at 168 hours from the start of the salt spray test, but rust formation was confirmed for one bolt at 336 hours from the start of the test. At 504 hours from the start of the test, rust formation was confirmed on three or more bolts, which was more than half of the five bolts. <Ejemplo 17> Five bolts that had undergone the base treatment and the immersion treatment were prepared the same as in Example 1, except that the rotational frequency of the centrifugal stirring in the centrifugation method in the base treatment was changed to change the amount of coating deposition containing zinc and aluminum to 14 g / m2. The five bolts prepared in this manner, which had undergone the base treatment (coating deposition rate: 14 g / m²) and the immersion treatment (aqueous sodium silicate solution; bolt surface temperature: 265°C to 300°C), were then subjected to a salt spray test in accordance with JIS Z-2371 i frfrenn / zznz / E / Yii in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts 1008 hours after the start of the salt spray test. <Ejemplo Comparativo 6> Five bolts that had been subjected only to the base treatment were prepared the same as in Example 17, except that after the base treatment, the immersion treatment with the aqueous solution containing 3% by mass of sodium silicate was not carried out and the bolts were cooled to room temperature as they were. The five bolts prepared in this manner, which had only undergone the base treatment (coating deposition rate: 14 g / m²), were then subjected to a salt spray test according to JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts at 168 hours from the start of the salt spray test, but rust formation was confirmed in two bolts at 336 hours from the start of the test. At 504 hours from the start of the test, rust formation was confirmed in three or more bolts, which was more than half of the five bolts.<Ejemplo 18> As a dip treatment agent, sodium dihydrogen phosphate was dissolved in deionized water to prepare 150 mL of an aqueous solution containing 5% by mass of sodium dihydrogen phosphate. The pH of the prepared dip treatment agent was 4.3. Five bolts that had undergone both the base treatment and the dip treatment were prepared in the same manner as in Example 17, except that the dip treatment was carried out using the 150 mL of the aqueous solution containing 5% by mass of sodium dihydrogen phosphate at a solution temperature of 20°C instead of the 150 mL of aqueous solution containing 3% by mass of sodium silicate at a solution temperature of 20°C. The five bolts prepared in this manner, which had undergone the base treatment (coating deposition rate: 14 g / m²) and the immersion treatment (aqueous sodium diacid phosphate solution; bolt surface temperature: 265°C to 300°C), were then subjected to a salt spray test in accordance with JIS Z-2371, in the same manner as Example 1, to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts 840 hours after the start of the salt spray test. <Ejemplo 19> As a dip treatment agent, potassium sulfate was dissolved in deionized water to prepare 150 mL of an aqueous solution containing 5% by mass of potassium sulfate. The pH of the prepared dip treatment agent was 5.8. Five bolts that had undergone the base treatment and the dip treatment were prepared in the same way as in Example 17, except that the dip treatment was carried out using the 150 mL of the aqueous solution containing 5% by mass of potassium sulfate at a solution temperature of 20°C instead of 150 mL of the aqueous solution containing 3% by mass of sodium silicate at a solution temperature of 20°C. The five bolts prepared in this manner, which had undergone the base treatment (coating deposition rate: 14 g / m²) and the immersion treatment (aqueous potassium sulfate solution; bolt surface temperature: 265°C to 300°C), were then subjected to a salt spray test in accordance with JIS Z-2371, in the same manner as Example 1, to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts 672 hours after the start of the salt spray test. <Ejemplo Comparativo 7> As an immersion treatment agent, sodium citrate was dissolved in deionized water to prepare 150 mL of an aqueous solution containing 5% by mass of sodium citrate. Five bolts that had undergone both the base treatment and the immersion treatment were prepared in the same way as in Example 17, except that the immersion treatment was carried out using the 150 mL of the aqueous solution containing 5% by mass of sodium citrate at a solution temperature of 20°C instead of 150 mL of the aqueous solution containing 3% by mass of sodium silicate at a solution temperature of 20°C. The five bolts prepared in this manner, which had undergone the base treatment (coating deposition rate: 14 g / m²) and the immersion treatment (aqueous sodium citrate solution; bolt surface temperature: 265°C to 300°C), were then subjected to a salt spray test in accordance with JIS Z-2371, in the same manner as Example 1, to evaluate corrosion resistance. As a result, rust formation was confirmed on three or more bolts, which was more than half of the five bolts, 168 hours after the start of the test.<Ejemplo 20> Five bolts that had undergone the base treatment and the immersion treatment were prepared the same as in Example 1, except that the rotational frequency of the centrifugal stirring in the centrifugation method in the base treatment was changed to change the amount of coating deposition containing zinc and aluminum to 18 g / m2. The five bolts prepared in this way, which had been subjected to the base treatment (the amount of coating deposition: 18 g / m2) and the immersion treatment (aqueous solution of sodium silicate; the surface temperature of the bolts: 265°C ai frfrenn / zznz / E / Yii The bolts were heated to 300°C, then subjected to a salt spray test in accordance with JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for any of the five bolts at 1008 hours from the start of the salt spray test. Similarly, at 1848 hours from the start of the test, rust formation was not confirmed for any of the five bolts. Rust formation was confirmed on only one bolt at 2016 hours from the start of the test. <Ejemplo Comparativo 8> Five bolts that had been subjected only to the base treatment were prepared the same as in Example 20, except that after the base treatment, the immersion treatment with the aqueous solution containing 3% by mass of sodium silicate was not carried out and the bolts were cooled to room temperature as they were. The five bolts prepared in this manner, which had only undergone the base treatment (coating deposition rate: 18 g / m²), were then subjected to a salt spray test in accordance with JIS Z-2371, in the same manner as Example 1, to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts at 504 hours from the start of the salt spray test, but rust formation was confirmed in three or more bolts, which was more than half of the five bolts, at 672 hours from the start of the test. <Ejemplo 21 > As a dip treatment agent, lithium silicate was dissolved in deionized water to prepare 150 mL of an aqueous solution containing 3% by mass of lithium silicate. The pH of the prepared dip treatment agent was 11.0. Five bolts that had undergone both the base treatment and the dip treatment were prepared in the same manner as in Example 20, except that the dip treatment was carried out using the 150 mL of the aqueous solution containing 3% by mass of lithium silicate at a solution temperature of 20°C instead of the 150 mL of aqueous solution containing 3% by mass of sodium silicate at a solution temperature of 20°C. The five bolts prepared in this manner, which had undergone the base treatment (coating deposition rate: 18 g / m²) and the immersion treatment (aqueous lithium silicate solution; bolt surface temperature: 265°C to 300°C), were then subjected to a salt spray test in accordance with JIS Z-2371, in the same manner as Example 1, to evaluate corrosion resistance. As a result, rust formation was not confirmed for any of the five bolts at 2148 hours from the start of the salt spray test. At 2352 hours from the start of the test, rust formation was confirmed for one bolt. <Ejemplo 22> As a dip treatment agent, potassium silicate was dissolved in deionized water to prepare 150 mL of an aqueous solution containing 3% by mass of potassium silicate. The pH of the prepared dip treatment agent was 11.4. Five bolts that had undergone both the base treatment and the dip treatment were prepared in the same manner as in Example 20, except that the dip treatment was carried out using 150 mL of the aqueous solution containing 3% by mass of potassium silicate at a solution temperature of 20°C instead of 150 mL of the aqueous solution containing 3% by mass of sodium silicate at a solution temperature of 20°C. The five bolts prepared in this manner, which had undergone the base treatment (coating deposition rate: 18 g / m²) and the immersion treatment (aqueous potassium silicate solution; bolt surface temperature: 265°C to 300°C), were then subjected to a salt spray test according to JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for any of the five bolts at 1848 hours from the start of the salt spray test. At 2016 hours from the start of the test, rust formation was confirmed in one bolt. Also, at 2352 hours from the start of the test, rust formation was confirmed in only one bolt. <Ejemplo 23> After the base treatment was carried out in the same manner as in Example 4, the surface temperature of five bolts removed from the electric furnace was confirmed to be between 265°C and 300°C using an infrared thermometer. The bolts were then immersed in 150 mL of the aqueous solution containing 3% by mass of sodium silicate at a solution temperature of 0°C for approximately 60 seconds. The bolts were then removed and dried to prepare five bolts that had undergone both the base treatment and the immersion treatment. The five bolts prepared in this manner, which had undergone the base treatment (coating deposition rate: 12 g / m²) and the immersion treatment (aqueous sodium silicate solution at 0°C; bolt surface temperature: 265°C to 300°C), were then subjected to a salt spray test in accordance with JIS Z-2371, in the same manner as Example 1, to evaluate corrosion resistance. As a result, rust formation was not confirmed for any of the five bolts at 1176 hours from the start of the salt spray test, and rust formation was confirmed on only one bolt at 1680 hours from the start of the test. <Ejemplo 24> Five bolts that had undergone the base treatment and the dip treatment were prepared in the same way as in Example 23, except that the temperature of the dip treatment agent solution, i.e. the aqueous solution containing 3% by mass of sodium silicate, was changed to 50°C. i frfrenn / zznz / E / Yi The five bolts prepared in this manner, which had undergone the base treatment (coating deposition rate: 12 g / m²) and the immersion treatment (aqueous sodium silicate solution at 50°C; bolt surface temperature: 265°C to 300°C), were then subjected to a salt spray test in accordance with JIS Z-2371, in the same manner as Example 1, to evaluate corrosion resistance. As a result, rust formation was not confirmed for any of the five bolts at 1176 hours from the start of the salt spray test, and rust formation was confirmed on only one bolt at 1680 hours from the start of the test. <Ejemplo 25> Five bolts that had undergone the base treatment and the dip treatment were prepared in the same way as in Example 23, except that the temperature of the dip treatment agent solution, i.e., the aqueous solution containing 3% by mass of sodium silicate, was changed to 90°C. The five bolts prepared in this manner, which had undergone the base treatment (coating deposition rate: 12 g / m²) and the immersion treatment (aqueous sodium silicate solution at 90°C; bolt surface temperature: 265°C to 300°C), were then subjected to a salt spray test in accordance with JIS Z-2371, in the same manner as Example 1, to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts 1176 hours after the start of the salt spray test. <Ejemplo 26> After the base treatment was carried out in the same manner as in Example 4, the surface temperature of five bolts removed from the electric oven was confirmed to be between 265°C and 300°C using an infrared thermometer. The bolts were then immersed in 150 mL of the aqueous solution containing 3 wt% sodium diacid phosphate at a solution temperature of 0°C for approximately 60 seconds. The bolts were then removed and dried to prepare five bolts that had undergone both the base treatment and the immersion treatment. The five bolts prepared in this manner, which had undergone the base treatment (coating deposition rate: 12 g / m²) and the immersion treatment (aqueous sodium dihydrogen phosphate solution at 0°C; bolt surface temperature: 265°C to 300°C), were then subjected to a salt spray test in accordance with JIS Z-2371, in the same manner as Example 1, to evaluate corrosion resistance. As a result, rust formation was not confirmed for any of the five bolts at 1176 hours from the start of the salt spray test, and rust formation was confirmed only on one bolt at 1680 hours from the start of the test. <Ejemplo 27> i frfrenn / zznz / E / Yi Five bolts that had undergone the base treatment and the dip treatment were prepared in the same way as in Example 26, except that the temperature of the dip treatment agent solution, i.e., the aqueous solution containing 3% by mass sodium diacid phosphate, was changed to 50°C. The five bolts prepared in this manner, which had undergone the base treatment (coating deposition rate: 12 g / m²) and the immersion treatment (aqueous sodium dihydrogen phosphate solution at 50°C; bolt surface temperature: 265°C to 300°C), were then subjected to a salt spray test in accordance with JIS Z-2371, in the same manner as Example 1, to evaluate corrosion resistance. As a result, rust formation was not confirmed for any of the five bolts at 840 hours from the start of the salt spray test, and rust formation was confirmed only on one bolt at 1176 hours from the start of the test. <Ejemplo 28> After the base treatment was carried out in the same manner as in Example 4, the surface temperature of five bolts removed from the electric furnace was confirmed to be between 265°C and 300°C using an infrared thermometer. The bolts were then immersed in an aqueous solution containing 3% by mass of sodium silicate, the weight of which was one time the total weight of the bolts to be immersed, at a solution temperature of 25°C for approximately 10 seconds. The bolts were then removed and dried to prepare five bolts that had undergone both the base treatment and the immersion treatment. The five bolts prepared in this manner, which had undergone the base treatment (coating deposition rate: 12 g / m²) and the immersion treatment (sodium silicate aqueous solution weighing one time the total weight of the bolts; bolt surface temperature: 265°C to 300°C), were then subjected to a salt spray test in accordance with JIS Z-2371, in the same manner as Example 1, to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts 2352 hours after the start of the salt spray test.<Ejemplo 29> Five bolts that had undergone the base treatment and the dip treatment were prepared the same as in Example 28, except that the amount used of the dip treatment agent, i.e., the aqueous solution containing 3% by mass of sodium silicate, was changed to an amount that weighs 3 times the total weight of the bolts. The five bolts prepared in this manner, which had undergone the base treatment (coating deposition rate: 12 g / m²) and the immersion treatment (sodium silicate aqueous solution weighing three times the total weight of the bolts; bolt surface temperature: 265°C to 300°C), were then subjected to a salt spray test in accordance with JIS Z-2371, in the same manner as Example 1, to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts 2352 hours after the start of the salt spray test.<Ejemplo 30> Five bolts that had undergone the base treatment and the dip treatment were prepared the same as in Example 28, except that the amount used of the dip treatment agent, i.e., the aqueous solution containing 3% by mass of sodium silicate, was changed to an amount that weighs 5 times the total weight of the bolts. The five bolts prepared in this manner, which had undergone the base treatment (coating deposition rate: 12 g / m²) and the immersion treatment (sodium silicate aqueous solution weighing five times the total weight of the bolts; bolt surface temperature: 265°C to 300°C), were then subjected to a salt spray test in accordance with JIS Z-2371, in the same manner as Example 1, to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts at 2520 hours from the start of the salt spray test.<Ejemplo 31 > Five bolts that had undergone the base treatment and the dip treatment were prepared in the same way as in Example 28, except that the amount used of the dip treatment agent, i.e., the aqueous solution containing 3% by mass of sodium silicate, was changed to an amount that weighs 10 times the total weight of the bolts. The five bolts prepared in this manner, which had undergone the base treatment (coating deposition rate: 12 g / m²) and the immersion treatment (sodium silicate aqueous solution weighing 10 times the total weight of the bolts; bolt surface temperature: 265°C to 300°C), were then subjected to a salt spray test in accordance with JIS Z-2371, in the same manner as Example 1, to evaluate corrosion resistance. As a result, rust formation was not confirmed for any of the five bolts at 2016 hours from the start of the salt spray test, and rust formation was confirmed in only one bolt at 2352 hours from the start of the test.<Ejemplo Comparativo 9> A base coating treatment agent containing zinc flakes as a main component was prepared in the same manner as Example 1. Next, five M6 flanged hex head bolts, which had been steam degreased with dichloromethane and shot blasted, were coated with the base coating treatment agent by an immersion method involving centrifugal agitation (an immersion centrifugation method), preheated to 100°C for 10 minutes in an electric oven, and baked at 330°C for 30 minutes in an electric oven to form a zinc-aluminum coating. The coating deposition rate was 12 g / m². From now on, this process for forming a zinc-aluminum coating will be referred to as the “base treatment.” The five bolts taken out of the electric oven were cooled to room temperature as found to prepare five bolts that had only undergone base treatment. The five bolts prepared in this manner, which had undergone only the base treatment, were then subjected to a salt spray test in accordance with JIS Z-2371, in the same manner as Example 1, to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts at 168 hours from the start of the salt spray test, but rust formation was confirmed in two bolts at 336 hours of the test. Rust formation was confirmed in three or more bolts, which was more than half of the five bolts, at 504 hours from the start of the test. <Ejemplo 32> In the same way as Comparative Example 9, five flanged hex head bolts of size M6, which had been subjected to dichloromethane steam degreasing and shot blasting, were coated with the treatment agent for the base coating by an immersion method involving centrifugal stirring (an immersion centrifugation method), preheated to 100°C for 10 minutes in an electric oven, and baked at 330°C for 30 minutes in an electric oven to form a coating containing zinc and aluminum. After this, the five bolts removed from the electric furnace were cooled to room temperature (around 25°C) and immersed in 150 mL of an aqueous solution containing 3% by mass of sodium silicate (pH 11.5) at a solution temperature of 25°C for about 10 seconds. The bolts were then removed and dried to prepare five bolts that had undergone both the base treatment and the immersion treatment. The five bolts prepared in this manner, which had undergone the base treatment and the immersion treatment (aqueous sodium silicate solution; bolt surface temperature: ambient temperature [approximately 25°C]), were then subjected to a salt spray test in accordance with JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts at 672 hours from the start of the salt spray test, and rust formation was confirmed only on two bolts at 840 hours from the start of the test. <Ejemplo 33> In the same way as Comparative Example 9, five flanged hex head bolts of size M6, which had been subjected to dichloromethane steam degreasing and shot blasting, were coated with the treatment agent for the base coating by an immersion method involving centrifugal stirring (an immersion centrifugation method), preheated to 100°C for 10 minutes in an electric oven, and baked at 330°C for 30 minutes in an electric oven to form a coating containing zinc and aluminum. Following this, the surface temperature of five bolts removed from the electric furnace was confirmed to be between 35°C and 60°C using an infrared thermometer. The bolts were then immersed in 150 mL of an aqueous solution containing 3% by mass of sodium silicate (pH 11.5) at a solution temperature of 25°C for approximately 10 seconds. The bolts were then removed and dried to prepare five bolts that had undergone both the base treatment and the immersion treatment. The five bolts prepared in this manner, which had undergone the base treatment and the immersion treatment (aqueous sodium silicate solution; bolt surface temperature: 35°C to 60°C), were then subjected to a salt spray test in accordance with JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts at 840 hours from the start of the salt spray test, and rust formation was confirmed in only two bolts at 1008 hours from the start of the test. <Ejemplo 34> In the same way as Comparative Example 9, five flanged hex head bolts of size M6, which had been subjected to dichloromethane steam degreasing and shot blasting, were coated with the treatment agent for the base coating by an immersion method involving centrifugal stirring (an immersion centrifugation method), preheated to 100°C for 10 minutes in an electric oven, and baked at 330°C for 30 minutes in an electric oven to form a coating containing zinc and aluminum. Following this, the surface temperature of five bolts removed from the electric furnace was confirmed to be between 65°C and 100°C using an infrared thermometer. The bolts were then immersed in 150 mL of an aqueous solution containing 3% by mass of sodium silicate (pH 11.5) at a solution temperature of 25°C for approximately 10 seconds. The bolts were then removed and dried to prepare five bolts that had undergone both the base treatment and the immersion treatment. The five bolts prepared in this manner, which had undergone the i frfrenn / zznz / E / Yii base treatment and immersion treatment (aqueous sodium silicate solution; bolt surface temperature: 65°C to 100°C), were then subjected to a salt spray test in accordance with JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts at 672 hours from the start of the salt spray test, and rust formation was confirmed in only two bolts at 840 hours from the start of the test. <Ejemplo 35> In the same way as Comparative Example 9, five flanged hex head bolts of size M6, which had been subjected to dichloromethane steam degreasing and shot blasting, were coated with the treatment agent for the base coating by an immersion method involving centrifugal stirring (an immersion centrifugation method), preheated to 100°C for 10 minutes in an electric oven, and baked at 330°C for 30 minutes in an electric oven to form a coating containing zinc and aluminum. Following this, the surface temperature of five bolts removed from the electric furnace was confirmed to be between 105°C and 140°C using an infrared thermometer. The bolts were then immersed in 150 mL of an aqueous solution containing 3% by mass of sodium silicate (pH 11.5) at a solution temperature of 25°C for approximately 10 seconds. The bolts were then removed and dried to prepare five bolts that had undergone both the base treatment and the immersion treatment. The five bolts prepared in this manner, which had undergone the base treatment and the immersion treatment (aqueous sodium silicate solution; bolt surface temperature: 105°C to 140°C), were then subjected to a salt spray test in accordance with JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts at 672 hours from the start of the salt spray test, and rust formation was confirmed in only two bolts at 840 hours from the start of the test. <Ejemplo 36> In the same way as Comparative Example 9, five flanged hex head bolts of size M6, which had been subjected to dichloromethane steam degreasing and shot blasting, were coated with the treatment agent for the base coating by an immersion method involving centrifugal stirring (an immersion centrifugation method), preheated to 100°C for 10 minutes in an electric oven, and baked at 330°C for 30 minutes in an electric oven to form a coating containing zinc and aluminum. After this, the surface temperature of five bolts removed from the electric furnace was confirmed to be between 145°C and 180°C using an infrared thermometer, and the bolts were immersed in 150 mL of the aqueous solution containing 3% by mass of sodium silicate (pH 11.5) at a solution temperature of 25°C for approximately 10 seconds. The bolts were then removed and dried to prepare five bolts that had undergone both the base treatment and the immersion treatment. The five bolts prepared in this manner, which had undergone the base treatment and the immersion treatment (aqueous sodium silicate solution; bolt surface temperature: 145°C to 180°C), were then subjected to a salt spray test in accordance with JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for any of the five bolts at 672 hours from the start of the salt spray test, and rust formation was confirmed on only one bolt at 840 hours from the start of the test. Similarly, at 1008 hours from the start of the test, rust formation was confirmed on only one bolt.<Ejemplo 37> In the same way as Comparative Example 9, five flanged hex head bolts of size M6, which had been subjected to dichloromethane steam degreasing and shot blasting, were coated with the treatment agent for the base coating by an immersion method involving centrifugal stirring (an immersion centrifugation method), preheated to 100°C for 10 minutes in an electric oven, and baked at 330°C for 30 minutes in an electric oven to form a coating containing zinc and aluminum. Following this, the surface temperature of five bolts removed from the electric furnace was confirmed to be between 185°C and 220°C using an infrared thermometer. The bolts were then immersed in 150 mL of an aqueous solution containing 3% by mass of sodium silicate (pH 11.5) at a solution temperature of 25°C for approximately 10 seconds. The bolts were then removed and dried to prepare five bolts that had undergone both the base treatment and the immersion treatment. The five bolts prepared in this manner, which had undergone the base treatment and the immersion treatment (aqueous sodium silicate solution; bolt surface temperature: 185°C to 220°C), were then subjected to a salt spray test in accordance with JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts at 1176 hours from the start of the salt spray test, and rust formation was confirmed in only one bolt at 1344 hours from the start of the test.<Ejemplo 38> In the same way as Comparative Example 9, five flanged hex head bolts of size M6, which had been subjected to dichloromethane steam degreasing and shot blasting, were coated with the treatment agent for the i frfrenn / zznz / E / Yii base coating by an immersion method involving centrifugal stirring (an immersion centrifugation method), preheated to 100°C for 10 minutes in an electric oven, and baked at 330°C for 30 minutes in an electric oven to form a coating containing zinc and aluminum. Following this, the surface temperature of five bolts removed from the electric furnace was confirmed to be between 225°C and 260°C using an infrared thermometer. The bolts were then immersed in 150 mL of an aqueous solution containing 3% by mass of sodium silicate (pH 11.5) at a solution temperature of 25°C for approximately 10 seconds. The bolts were then removed and dried to prepare five bolts that had undergone both the base treatment and the immersion treatment. The five bolts prepared in this manner, which had undergone the base treatment and the immersion treatment (aqueous sodium silicate solution; bolt surface temperature: 225°C to 260°C), were then subjected to a salt spray test in accordance with JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts at 1176 hours from the start of the salt spray test, and rust formation was confirmed only on one bolt at 1344 hours from the start of the test. <Ejemplo 39> In the same way as Comparative Example 9, five flanged hex head bolts of size M6, which had been subjected to dichloromethane steam degreasing and shot blasting, were coated with the treatment agent for the base coating by an immersion method involving centrifugal stirring (an immersion centrifugation method), preheated to 100°C for 10 minutes in an electric oven, and baked at 330°C for 30 minutes in an electric oven to form a coating containing zinc and aluminum. Following this, the surface temperature of five bolts removed from the electric furnace was confirmed to be between 265°C and 300°C using an infrared thermometer. The bolts were then immersed in 150 mL of an aqueous solution containing 3% by mass of sodium silicate (pH 11.5) at a solution temperature of 25°C for approximately 10 seconds. The bolts were then removed and dried to prepare five bolts that had undergone both the base treatment and the immersion treatment. The five bolts prepared in this manner, which had undergone the base treatment and the immersion treatment (aqueous sodium silicate solution; bolt surface temperature: 265°C to 300°C), were then subjected to a salt spray test in accordance with JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts at 1176 hours from the start of the salt spray test, and rust formation was confirmed only on one bolt at 1344 hours from the start of the test.<Ejemplo 40> In the same way as Comparative Example 9, five flanged hex head bolts of size M6, which had been subjected to dichloromethane steam degreasing and shot blasting, were coated with the treatment agent for the base coating by an immersion method involving centrifugal stirring (an immersion centrifugation method), preheated to 100°C for 10 minutes in an electric oven, and baked at 330°C for 30 minutes in an electric oven to form a coating containing zinc and aluminum. After this, the five bolts removed from the electric oven were cooled to room temperature (around 25°C) and immersed in 150 mL of an aqueous solution containing 3% by mass sodium diacid phosphate (pH 4.4) at a solution temperature of 25°C for about 10 seconds. The bolts were then removed and dried to prepare five bolts that had undergone both the base treatment and the immersion treatment. The five bolts prepared in this manner, which had undergone the base treatment and the immersion treatment (aqueous sodium diacid phosphate solution; bolt surface temperature: ambient temperature [approximately 25°C]), were then subjected to a salt spray test in accordance with JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts at 336 hours from the start of the salt spray test, and rust formation was confirmed in only two bolts at 504 hours from the start of the test. <Ejemplo 41 > In the same way as Comparative Example 9, five flanged hex head bolts of size M6, which had been subjected to dichloromethane steam degreasing and shot blasting, were coated with the treatment agent for the base coating by an immersion method involving centrifugal stirring (an immersion centrifugation method), preheated to 100°C for 10 minutes in an electric oven, and baked at 330°C for 30 minutes in an electric oven to form a coating containing zinc and aluminum. Following this, the surface temperature of five bolts removed from the electric oven was confirmed to be between 35°C and 60°C using an infrared thermometer. The bolts were then immersed in 150 mL of an aqueous solution containing 3% by mass sodium diacid phosphate (pH 4.4) at a solution temperature of 25°C for approximately 10 seconds. The bolts were then removed and dried to prepare five bolts that had undergone both the base treatment and the immersion treatment. i frfrenn / zznz / E / Yii The five bolts prepared in this manner, which had undergone the base treatment and the immersion treatment (aqueous sodium diacid phosphate solution; bolt surface temperature: 35°C to 60°C), were then subjected to a salt spray test in accordance with JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts at 336 hours from the start of the salt spray test, and rust formation was confirmed in only two bolts at 504 hours from the start of the test. <Ejemplo 42> In the same way as Comparative Example 9, five flanged hex head bolts of size M6, which had been subjected to dichloromethane steam degreasing and shot blasting, were coated with the treatment agent for the base coating by an immersion method involving centrifugal stirring (an immersion centrifugation method), preheated to 100°C for 10 minutes in an electric oven, and baked at 330°C for 30 minutes in an electric oven to form a coating containing zinc and aluminum. Following this, the surface temperature of five bolts removed from the electric oven was confirmed to be between 65°C and 100°C using an infrared thermometer. The bolts were then immersed in 150 mL of an aqueous solution containing 3% by mass sodium diacid phosphate (pH 4.4) at a solution temperature of 25°C for approximately 10 seconds. The bolts were then removed and dried to prepare five bolts that had undergone both the base treatment and the immersion treatment. The five bolts prepared in this manner, which had undergone the base treatment and the immersion treatment (aqueous sodium dihydrogen phosphate solution; bolt surface temperature: 65°C to 100°C), were then subjected to a salt spray test in accordance with JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts at 336 hours from the start of the salt spray test, and rust formation was confirmed in only one bolt at 504 hours from the start of the test. Rust formation was confirmed in only two bolts at 672 hours from the start of the test. <Ejemplo 43> In the same way as Comparative Example 9, five flanged hex head bolts of size M6, which had been subjected to dichloromethane steam degreasing and shot blasting, were coated with the treatment agent for the base coating by an immersion method involving centrifugal stirring (an immersion centrifugation method), preheated to 100°C for 10 minutes in an electric oven, and baked at 330°C for 30 minutes in an electric oven to form a coating containing zinc and aluminum. i frfrenn / zznz / E / Yii Following this, the surface temperature of five bolts removed from the electric oven was confirmed to be between 105°C and 140°C using an infrared thermometer. The bolts were then immersed in 150 mL of an aqueous solution containing 3% by mass sodium diacid phosphate (pH 4.4) at a solution temperature of 25°C for approximately 10 seconds. The bolts were then removed and dried to prepare five bolts that had undergone both the base treatment and the immersion treatment. The five bolts prepared in this manner, which had undergone the base treatment and the immersion treatment (aqueous sodium dihydrogen phosphate solution; bolt surface temperature: 105°C to 140°C), were then subjected to a salt spray test in accordance with JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts at 504 hours from the start of the salt spray test, and rust formation was confirmed in only two bolts at 672 hours from the start of the test. <Ejemplo 44> In the same way as Comparative Example 9, five flanged hex head bolts of size M6, which had been subjected to dichloromethane steam degreasing and shot blasting, were coated with the treatment agent for the base coating by an immersion method involving centrifugal stirring (an immersion centrifugation method), preheated to 100°C for 10 minutes in an electric oven, and baked at 330°C for 30 minutes in an electric oven to form a coating containing zinc and aluminum. Following this, the surface temperature of five bolts removed from the electric oven was confirmed to be between 145°C and 180°C using an infrared thermometer. The bolts were then immersed in 150 mL of an aqueous solution containing 3% by mass sodium diacid phosphate (pH 4.4) at a solution temperature of 25°C for approximately 10 seconds. The bolts were then removed and dried to prepare five bolts that had undergone both the base treatment and the immersion treatment. The five bolts prepared in this manner, which had undergone the base treatment and the immersion treatment (aqueous sodium diacid phosphate solution; bolt surface temperature: 145°C to 180°C), were then subjected to a salt spray test in accordance with JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts at 504 hours from the start of the salt spray test, and rust formation was confirmed in only one bolt at 840 hours from the start of the test. Rust formation was confirmed in only two bolts at 1008 hours from the start of the test. <Ejemplo 45> In the same way as Comparative Example 9, five flanged hex head bolts of size M6, which had been steam degreased with dichloromethane and shot blasted, were coated with the treatment agent for the base coating by an immersion method involving centrifugal stirring (an immersion centrifugation method), preheated to 100°C for 10 minutes in an electric oven, and baked at 330°C for 30 minutes in an electric oven to form a coating containing zinc and aluminum. Following this, the surface temperature of five bolts removed from the electric oven was confirmed to be between 185°C and 220°C using an infrared thermometer. The bolts were then immersed in 150 mL of an aqueous solution containing 3% by mass sodium diacid phosphate (pH 4.4) at a solution temperature of 25°C for approximately 10 seconds. The bolts were then removed and dried to prepare five bolts that had undergone both the base treatment and the immersion treatment. The five bolts prepared in this manner, which had undergone the base treatment and the immersion treatment (aqueous sodium diacid phosphate solution; bolt surface temperature: 185°C to 220°C), were then subjected to a salt spray test in accordance with JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts at 840 hours from the start of the salt spray test. <Ejemplo 46> In the same way as Comparative Example 9, five flanged hex head bolts of size M6, which had been subjected to dichloromethane steam degreasing and shot blasting, were coated with the treatment agent for the base coating by an immersion method involving centrifugal stirring (an immersion centrifugation method), preheated to 100°C for 10 minutes in an electric oven, and baked at 330°C for 30 minutes in an electric oven to form a coating containing zinc and aluminum. Following this, the surface temperature of five bolts removed from the electric oven was confirmed to be between 225°C and 260°C using an infrared thermometer. The bolts were then immersed in 150 mL of an aqueous solution containing 3% by mass sodium diacid phosphate (pH 4.4) at a solution temperature of 25°C for approximately 10 seconds. The bolts were then removed and dried to prepare five bolts that had undergone both the base treatment and the immersion treatment. The five bolts prepared in this manner, which had undergone the base treatment and the immersion treatment (aqueous sodium dihydrogen phosphate solution; bolt surface temperature: 225°C to 260°C), were then subjected to a salt spray test in accordance with JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts at 672 hours from the start of the salt spray test, and rust formation was confirmed on only one bolt at 840 hours from the start of the test. <Ejemplo 47> In the same way as Comparative Example 9, five flanged hex head bolts of size M6, which had been subjected to dichloromethane steam degreasing and shot blasting, were coated with the treatment agent for the base coating by an immersion method involving centrifugal stirring (an immersion centrifugation method), preheated to 100°C for 10 minutes in an electric oven, and baked at 330°C for 30 minutes in an electric oven to form a coating containing zinc and aluminum. Following this, the surface temperature of five bolts removed from the electric oven was confirmed to be between 265°C and 300°C using an infrared thermometer. The bolts were then immersed in 150 mL of an aqueous solution containing 3% by mass sodium diacid phosphate (pH 4.4) at a solution temperature of 25°C for approximately 10 seconds. The bolts were then removed and dried to prepare five bolts that had undergone both the base treatment and the immersion treatment. The five bolts prepared in this manner, which had undergone the base treatment and the immersion treatment (aqueous sodium dihydrogen phosphate solution; bolt surface temperature: 265°C to 300°C), were then subjected to a salt spray test in accordance with JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts at 840 hours from the start of the salt spray test. <Ejemplo 48> In the same way as Comparative Example 9, five flanged hex head bolts of size M6, which had been subjected to dichloromethane steam degreasing and shot blasting, were coated with the treatment agent for the base coating by an immersion method involving centrifugal stirring (an immersion centrifugation method), preheated to 100°C for 10 minutes in an electric oven, and baked at 330°C for 30 minutes in an electric oven to form a coating containing zinc and aluminum. Following this, the surface temperature of five bolts removed from the electric furnace was confirmed to be between 65°C and 100°C using an infrared thermometer. The bolts were then immersed in 150 mL of an aqueous solution containing 5% ammonium zirconium carbonate by mass (pH 9.1) at a solution temperature of 25°C for approximately 10 seconds. The bolts were then removed and dried to prepare five bolts that had undergone both the base treatment and the immersion treatment. The five bolts prepared in this manner, which had undergone the i frfrenn / zznz / E / Yii base treatment and immersion treatment (aqueous ammonium zirconium carbonate solution; bolt surface temperature: 65°C to 100°C), were then subjected to a salt spray test in accordance with JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts at 336 hours from the start of the salt spray test, and rust formation was confirmed in only one bolt at 504 hours from the start of the test. Rust formation was confirmed in only two bolts at 672 hours from the start of the test.<Ejemplo 49> In the same way as Comparative Example 9, five flanged hex head bolts of size M6, which had been subjected to dichloromethane steam degreasing and shot blasting, were coated with the treatment agent for the base coating by an immersion method involving centrifugal stirring (an immersion centrifugation method), preheated to 100°C for 10 minutes in an electric oven, and baked at 330°C for 30 minutes in an electric oven to form a coating containing zinc and aluminum. Following this, the surface temperature of five bolts removed from the electric furnace was confirmed to be between 105°C and 140°C using an infrared thermometer. The bolts were then immersed in 150 mL of an aqueous solution containing 5% by mass of ammonium zirconium carbonate (pH 9.1) at a solution temperature of 25°C for approximately 10 seconds. The bolts were then removed and dried to prepare five bolts that had undergone both the base treatment and the immersion treatment. The five bolts prepared in this manner, which had undergone the base treatment and the immersion treatment (aqueous ammonium zirconium carbonate solution; bolt surface temperature: 105°C to 140°C), were then subjected to a salt spray test in accordance with JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts at 504 hours from the start of the salt spray test, and rust formation was confirmed in only two bolts at 672 hours from the start of the test.<Ejemplo 50> In the same way as Comparative Example 9, five flanged hex head bolts of size M6, which had been subjected to dichloromethane steam degreasing and shot blasting, were coated with the treatment agent for the base coating by an immersion method involving centrifugal stirring (an immersion centrifugation method), preheated to 100°C for 10 minutes in an electric oven, and baked at 330°C for 30 minutes in an electric oven to form a coating containing zinc and aluminum. Following this, the surface temperature of five i frfrenn / zznz / E / Yii bolts removed from the electric oven was confirmed to be between 145°C and 180°C using an infrared thermometer. The bolts were then immersed in 150 mL of an aqueous solution containing 5% by mass of ammonium zirconium carbonate (pH 9.1) at a solution temperature of 25°C for approximately 10 seconds. The bolts were then removed and dried to prepare five bolts that had undergone both the base treatment and the immersion treatment. The five bolts prepared in this manner, which had undergone the base treatment and the immersion treatment (aqueous ammonium zirconium carbonate solution; bolt surface temperature: 145°C to 180°C), were then subjected to a salt spray test in accordance with JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts at 840 hours from the start of the salt spray test, and rust formation was confirmed only on one bolt at 1008 hours from the start of the test.<Ejemplo 51 > In the same way as Comparative Example 9, five flanged hex head bolts of size M6, which had been subjected to dichloromethane steam degreasing and shot blasting, were coated with the treatment agent for the base coating by an immersion method involving centrifugal stirring (an immersion centrifugation method), preheated to 100°C for 10 minutes in an electric oven, and baked at 330°C for 30 minutes in an electric oven to form a coating containing zinc and aluminum. Following this, the surface temperature of five bolts removed from the electric furnace was confirmed to be between 145°C and 180°C using an infrared thermometer. The bolts were then immersed in 150 mL of an aqueous solution containing 5% ammonium zirconium carbonate by mass (pH 9.1) at a solution temperature of 25°C for approximately 10 seconds. The bolts were then removed and dried to prepare five bolts that had undergone both the base treatment and the immersion treatment. The five bolts prepared in this manner, which had undergone the base treatment and the immersion treatment (aqueous ammonium zirconium carbonate solution; bolt surface temperature: 145°C to 180°C), were then subjected to a salt spray test in accordance with JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts at 840 hours from the start of the salt spray test, and rust formation was confirmed only on one bolt at 1008 hours from the start of the test.<Ejemplo 52> In the same way as Comparative Example 9, five flanged hex head bolts of size M6, which had been subjected to dichloromethane steam degreasing and shot blasting, were coated with the treatment agent for the i frfrenn / zznz / E / Yii base coating by an immersion method involving centrifugal stirring (an immersion centrifugation method), preheated to 100°C for 10 minutes in an electric oven, and baked at 330°C for 30 minutes in an electric oven to form a coating containing zinc and aluminum. Following this, the surface temperature of five bolts removed from the electric furnace was confirmed to be between 225°C and 260°C using an infrared thermometer. The bolts were then immersed in 150 mL of an aqueous solution containing 5% ammonium zirconium carbonate by mass (pH 9.1) at a solution temperature of 25°C for approximately 10 seconds. The bolts were then removed and dried to prepare five bolts that had undergone both the base treatment and the immersion treatment. The five bolts prepared in this manner, which had undergone the base treatment and the immersion treatment (aqueous ammonium zirconium carbonate solution; bolt surface temperature: 225°C to 260°C), were then subjected to a salt spray test in accordance with JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts 1176 hours after the start of the salt spray test.<Ejemplo 53> In the same way as Comparative Example 9, five flanged hex head bolts of size M6, which had been subjected to dichloromethane steam degreasing and shot blasting, were coated with the treatment agent for the base coating by an immersion method involving centrifugal stirring (an immersion centrifugation method), preheated to 100°C for 10 minutes in an electric oven, and baked at 330°C for 30 minutes in an electric oven to form a coating containing zinc and aluminum. Following this, the surface temperature of five bolts removed from the electric furnace was confirmed to be between 265°C and 300°C using an infrared thermometer. The bolts were then immersed in 150 mL of an aqueous solution containing 5% by mass of ammonium zirconium carbonate (pH 9.1) at a solution temperature of 25°C for approximately 10 seconds. The bolts were then removed and dried to prepare five bolts that had undergone both the base treatment and the immersion treatment. The five bolts prepared in this manner, which had undergone the base treatment and the immersion treatment (aqueous ammonium zirconium carbonate solution; bolt surface temperature: 265°C to 300°C), were then subjected to a salt spray test in accordance with JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts 1176 hours after the start of the salt spray test.<Ejemplo Comparativo 10> i frfrenn / zznz / E / Yii In the same way as Comparative Example 9, five flanged hex head bolts of size M6, which had been subjected to dichloromethane steam degreasing and shot blasting, were coated with the treatment agent for the base coating by an immersion method involving centrifugal stirring (an immersion centrifugation method), preheated to 100°C for 10 minutes in an electric oven, and baked at 330°C for 30 minutes in an electric oven to form a coating containing zinc and aluminum. Following this, the surface temperature of five bolts removed from the electric oven was confirmed to be between 145°C and 180°C using an infrared thermometer. The bolts were then immersed in 150 mL of an aqueous solution containing 5% by mass potassium sulfate (pH 5.8) at a solution temperature of 25°C for approximately 10 seconds. The bolts were then removed and dried to prepare five bolts that had undergone both the base treatment and the immersion treatment. The five bolts prepared in this manner, which had undergone the base treatment and the immersion treatment (aqueous potassium sulfate solution; bolt surface temperature: 145°C to 180°C), were then subjected to a salt spray test in accordance with JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts at 168 hours from the start of the salt spray test, but rust formation was confirmed for one bolt at 336 hours from the start of the test. Rust formation was confirmed for two or more bolts at 504 hours from the start of the test. <Ejemplo 54> In the same way as Comparative Example 9, five flanged hex head bolts of size M6, which had been subjected to dichloromethane steam degreasing and shot blasting, were coated with the treatment agent for the base coating by an immersion method involving centrifugal stirring (an immersion centrifugation method), preheated to 100°C for 10 minutes in an electric oven, and baked at 330°C for 30 minutes in an electric oven to form a coating containing zinc and aluminum. Following this, the surface temperature of five bolts removed from the electric oven was confirmed to be between 225°C and 260°C using an infrared thermometer. The bolts were then immersed in 150 mL of an aqueous solution containing 5% by mass potassium sulfate (pH 5.8) at a solution temperature of 25°C for approximately 10 seconds. The bolts were then removed and dried to prepare five bolts that had undergone both the base treatment and the immersion treatment. The five bolts prepared in this manner, which had undergone the base treatment and the immersion treatment (aqueous potassium sulfate solution; surface temperature of the bolts: 225°C to 260°C), were then subjected to a salt spray test in accordance with JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts at 336 hours from the start of the salt spray test, and rust formation was confirmed in only one bolt at 504 hours from the start of the test. Rust formation was confirmed in only two bolts at 672 hours from the start of the test. <Ejemplo 55> In the same way as Comparative Example 9, five flanged hex head bolts of size M6, which had been subjected to dichloromethane steam degreasing and shot blasting, were coated with the treatment agent for the base coating by an immersion method involving centrifugal stirring (an immersion centrifugation method), preheated to 100°C for 10 minutes in an electric oven, and baked at 330°C for 30 minutes in an electric oven to form a coating containing zinc and aluminum. Following this, the surface temperature of five bolts removed from the electric oven was confirmed to be between 265°C and 300°C using an infrared thermometer. The bolts were then immersed in 150 mL of an aqueous solution containing 5% by mass potassium sulfate (pH 5.8) at a solution temperature of 25°C for approximately 10 seconds. The bolts were then removed and dried to prepare five bolts that had undergone both the base treatment and the immersion treatment. The five bolts prepared in this manner, which had undergone the base treatment and the immersion treatment (aqueous potassium sulfate solution; bolt surface temperature: 265°C to 300°C), were then subjected to a salt spray test in accordance with JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts at 504 hours from the start of the salt spray test, and rust formation was confirmed in only one bolt at 672 hours from the start of the test. <Ejemplo Comparativo 11 > In the same way as Comparative Example 9, five flanged hex head bolts of size M6, which had been subjected to dichloromethane steam degreasing and shot blasting, were coated with the treatment agent for the base coating by an immersion method involving centrifugal stirring (an immersion centrifugation method), preheated to 100°C for 10 minutes in an electric oven, and baked at 330°C for 30 minutes in an electric oven to form a coating containing zinc and aluminum. After this, the surface temperature of five bolts removed from the electric oven was confirmed to be between 145°C and 180°C using an infrared thermometer, and the bolts were immersed in 150 mL of the aqueous solution containing 5% by mass of sodium nitrate (pH 6.8) at a solution temperature of 25°C for approximately 10 seconds. The bolts were then removed and dried to prepare five bolts that had undergone both the base treatment and the immersion treatment. The five bolts prepared in this manner, which had undergone the base treatment and the immersion treatment (aqueous sodium nitrate solution; bolt surface temperature: 145°C to 180°C), were then subjected to a salt spray test in accordance with JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts at 168 hours from the start of the salt spray test, but rust formation was confirmed for one bolt at 336 hours from the start of the test. Rust formation was confirmed for two or more bolts at 672 hours from the start of the test. <Ejemplo 56> In the same way as Comparative Example 9, five flanged hex head bolts of size M6, which had been subjected to dichloromethane steam degreasing and shot blasting, were coated with the treatment agent for the base coating by an immersion method involving centrifugal stirring (an immersion centrifugation method), preheated to 100°C for 10 minutes in an electric oven, and baked at 330°C for 30 minutes in an electric oven to form a coating containing zinc and aluminum. Following this, the surface temperature of five bolts removed from the electric oven was confirmed to be between 225°C and 260°C using an infrared thermometer. The bolts were then immersed in 150 mL of an aqueous solution containing 5% by mass of sodium nitrate (pH 6.8) at a solution temperature of 25°C for approximately 10 seconds. The bolts were then removed and dried to prepare five bolts that had undergone both the base treatment and the immersion treatment. The five bolts prepared in this manner, which had undergone the base treatment and the immersion treatment (aqueous sodium nitrate solution; bolt surface temperature: 225°C to 260°C), were then subjected to a salt spray test in accordance with JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts at 336 hours from the start of the salt spray test, and rust formation was confirmed in only one bolt at 504 hours from the start of the test. Rust formation was confirmed in only two bolts at 672 hours from the start of the test. <Ejemplo 57> In the same way as Comparative Example 9, five flanged hex head bolts of size M6, which had been subjected to degreasing with dichloromethane steam and shot blasting, were coated with the treatment agent for the base coating by an immersion method involving centrifugal stirring (an immersion centrifugation method), preheated to 100°C for 10 minutes in an electric oven, and baked at 330°C for 30 minutes in an electric oven to form a coating containing zinc and aluminum. Following this, the surface temperature of five bolts removed from the electric furnace was confirmed to be between 265°C and 300°C using an infrared thermometer. The bolts were then immersed in 150 mL of an aqueous solution containing 5% by mass of sodium nitrate (pH 6.8) at a solution temperature of 25°C for approximately 10 seconds. The bolts were then removed and dried to prepare five bolts that had undergone both the base treatment and the immersion treatment. The five bolts prepared in this manner, which had undergone the base treatment and the immersion treatment (aqueous sodium nitrate solution; bolt surface temperature: 265°C to 300°C), were then subjected to a salt spray test in accordance with JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was not confirmed for the five bolts at 504 hours from the start of the salt spray test, and rust formation was confirmed in only one bolt at 672 hours from the start of the test. <Ejemplo Comparativo 12> In the same way as Comparative Example 9, five flanged hex head bolts of size M6, which had been subjected to dichloromethane steam degreasing and shot blasting, were coated with the treatment agent for the base coating by an immersion method involving centrifugal stirring (an immersion centrifugation method), preheated to 100°C for 10 minutes in an electric oven, and baked at 330°C for 30 minutes in an electric oven to form a coating containing zinc and aluminum. After this, the five bolts removed from the electric oven were cooled to room temperature (around 25°C) and immersed in 150 mL of an aqueous solution containing 5% sodium citrate by mass at a solution temperature of 25°C for about 10 seconds. The bolts were then removed and dried to prepare five bolts that had undergone both the base treatment and the immersion treatment. The five bolts prepared in this manner, which had undergone the base treatment and the immersion treatment (aqueous sodium citrate solution; bolt surface temperature: ambient temperature [approximately 25°C]), were then subjected to a salt spray test in accordance with JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was confirmed on one of the five bolts at 168 hours from the start of the salt spray test. At 336 hours from the start of the test, rust formation was confirmed on two bolts. <Ejemplo Comparativo 13> In the same way as Comparative Example 9, five flanged hex head bolts of size M6, which had been subjected to dichloromethane steam degreasing and shot blasting, were coated with the treatment agent for the base coating by an immersion method involving centrifugal stirring (an immersion centrifugation method), preheated to 100°C for 10 minutes in an electric oven, and baked at 330°C for 30 minutes in an electric oven to form a coating containing zinc and aluminum. Following this, the surface temperature of five bolts removed from the electric oven was confirmed to be between 225°C and 260°C using an infrared thermometer. The bolts were then immersed in 150 mL of an aqueous solution containing 5% sodium citrate at a solution temperature of 25°C for approximately 10 seconds. The bolts were then removed and dried to prepare five bolts that had undergone both the base treatment and the immersion treatment. The five bolts prepared in this manner, which had undergone the base treatment and the immersion treatment (aqueous sodium citrate solution; bolt surface temperature: 225°C to 260°C), were then subjected to a salt spray test in accordance with JIS Z-2371 in the same manner as Example 1 to evaluate corrosion resistance. As a result, rust formation was confirmed on one of the five bolts 168 hours after the start of the salt spray test. At 336 hours after the start of the test, rust formation was confirmed on two bolts. <Ejemplo 58> As a dip treatment agent, sodium silicate was dissolved in deionized water to prepare an aqueous solution containing 5% by mass of sodium silicate. The pH of the prepared dip treatment agent was 11.4 (20°C). Next, a cold-rolled steel sheet measuring 150 mm × 70 mm × 0.8 mm was degreased with dichloromethane and then heated in an electric furnace at 330°C for 15 minutes. After confirming that the surface temperature of the cold-rolled steel sheet removed from the electric furnace was between 265°C and 300°C using an infrared thermometer, the cold-rolled steel sheet was immersed in 150 mL of an aqueous solution containing 5% by mass of sodium silicate at a solution temperature of 20°C for approximately 10 seconds, then removed and dried. The cold-rolled steel sheet, which had been subjected to immersion treatment in this manner, was then subjected to a salt spray test in accordance with JIS Z-2371 to evaluate corrosion resistance. Figures 1A and 1B are photographs of the cold-rolled steel sheet that had been subjected to immersion treatment, at 1 hour and 5 hours from the start of the salt spray test, respectively. <Ejemplo Comparativo 14> A cold-rolled steel sheet for corrosion resistance evaluation was prepared in the same manner as Example 58, except that after heating in an electric furnace at 330°C for 15 minutes, the immersion treatment with the aqueous sodium silicate solution was not carried out and the sheet was cooled to room temperature as it was. The cold-rolled steel sheet that had not undergone immersion treatment was then subjected to a salt spray test in accordance with JIS Z-2371 to evaluate corrosion resistance. Figures 2A and 2B are photographs of the cold-rolled steel sheet that had not undergone immersion treatment, 1 hour and 5 hours after the start of the salt spray test, respectively. The cold-rolled steel sheet of Example 58, which had been subjected to immersion treatment with the aqueous sodium silicate solution, prevented rust formation as compared to the cold-rolled steel sheet of Comparative Example 14, which had not been subjected to immersion treatment. <Ejemplo 59> By uniformly mixing the following components, a base coating treatment agent containing zinc flakes as a main component was prepared. Deionized water: 39.06% by mass Zinc flakes: 32.12% by mass Aluminum flakes: 5.08% by mass DPG (dipropylene glycol): 10.29% by mass Synperonic (registered trademark) 13 / 6.5: 3.15% by mass Silquest (registered trademark) A187: 8.66% by mass Schwego foam (registered trademark): 0.40% by mass Ñipar (registered trademark) S10: 0.71% by mass Aerosol (registered trademark) TR70: 0.53% by mass The components listed above under the product names are as follows. Synperonic (registered trademark) 13 / 6.5: polyoxyethylene (6.5) surfactant Silquest (registered trademark) A187: y-glycidoxypropyltrimethoxysilane Schwego foam (registered trademark): defoamer i frfrenn / zznz / E / Yii Ñipar (registered trademark) S10:1-nitropropane Aerosol (registered trademark) TR70: anionic surfactant (bistridecyl sodium sulfosuccinate) Additionally, as an immersion treatment agent, sodium silicate was dissolved in deionized water containing 1% by mass of sodium silicate to prepare 1000 mL of an aqueous solution containing 1% by mass of sodium silicate. Next, five M10 flanged hex head bolts, which had been steam degreased with dichloromethane and shot blasted, were coated with the base coating treatment agent by an immersion method involving centrifugal agitation (an immersion centrifuge method), preheated to 100°C for 10 minutes in an electric oven, and baked at 330°C for 30 minutes in an electric oven to form a zinc-aluminum coating. The coating deposition rate was 14 g / m². From now on, this process for forming a zinc-aluminum coating will be referred to as the “base treatment.” It was then confirmed that the surface temperature of five bolts removed from the electric furnace was between 185°C and 220°C using an infrared thermometer. The bolts were immersed in 1000 mL of an aqueous solution containing 1% by mass of sodium silicate at a solution temperature of 20°C for approximately 1 minute. The bolts were then removed and dried to prepare five bolts that had undergone both the base treatment and the immersion treatment. The five bolts prepared in this manner, which had undergone the base treatment and the immersion treatment (aqueous solution containing 1% by mass of sodium silicate; bolt surface temperature: 185°C to 220°C), were then subjected to a surface friction coefficient measurement according to ISO 16047 HH to calculate the average friction coefficient value. The average friction coefficient was 0.243. The five bolts prepared in this manner, which had undergone base treatment and immersion treatment (aqueous solution containing 1% by mass of sodium silicate; bolt surface temperature: 185°C to 220°C), were then subjected to a salt spray test in accordance with JIS Z-2371. Rust formation was confirmed on the bolts every 168 hours from the start of the test to assess corrosion resistance. As a result, rust formation was not confirmed for any of the five bolts at 1176 hours from the start of the salt spray test, and rust formation was confirmed on only one bolt at 1344 hours from the start of the test. <Ejemplo 60> As an immersion treatment agent, sodium silicate AND A lubricant, i frfrenn / zznz / E / Yii “AQUACER 593” (product name) available from BYK Corporation (hereafter referred to as “lubricant a”) was dissolved and mixed in deionized water to thereby include 1% by mass of sodium silicate and 1% by mass of lubricant to prepare 1000 mL of an aqueous solution containing 1% by mass of sodium silicate and 1% by mass of lubricant a. Five bolts that had undergone the base treatment and the dip treatment were prepared the same as in Example 59, except that the dip treatment was carried out using 1000 mL of the aqueous solution containing 1% by mass of sodium silicate and 1% by mass of lubricant a at a solution temperature of 20°C instead of 1000 mL of the aqueous solution containing 1% by mass of sodium silicate at a solution temperature of 20°C.Note that lubricant a (“AQUACER 593” available from BYK Corporation) is an aqueous emulsion that includes a modified polypropylene wax as a base. The five bolts prepared in this way, which had been subjected to the base treatment and the immersion treatment (aqueous solution containing 1% by mass of sodium silicate and 1% by mass of lubricant a; surface temperature of the bolts: 185°C to 220°C), were then subjected to a measurement of the surface coefficient of friction according to the ISO16047 HH method to calculate the average value of the coefficient of friction in the same way as Example 59. The average coefficient of friction was 0.173. The five bolts prepared in this manner, which had undergone the base treatment and the immersion treatment (aqueous solution containing 1% by mass of sodium silicate and 1% by mass of lubricant a; bolt surface temperature: 185°C to 220°C), were then subjected to a salt spray test in accordance with JIS Z-2371, and it was confirmed whether the bolts had rusted every 168 hours from the start of the test to evaluate corrosion resistance, in the same manner as Example 59. As a result, rust formation was not confirmed for the five bolts at 1176 hours from the start of the salt spray test. <Ejemplo 61 > As a dip treatment agent, sodium silicate, and lubricant, “AQUACER 593” (product name) available from BYK Corporation (lubricant a) was dissolved and mixed in deionized water to include 1% by mass of sodium silicate and 5% by mass of the lubricant to prepare 1000 mL of an aqueous solution containing 1% by mass of sodium silicate and 5% by mass of lubricant a. Five bolts that had undergone the base treatment and the dip treatment were prepared in the same way as in Example 59, except that the dip treatment was carried out using 1000 mL of the aqueous solution containing 1% by mass of sodium silicate and 5% by mass of lubricant a at a solution temperature of 20°C instead of 1000 mL of the aqueous solution containing 1% by mass of sodium silicate at a solution temperature of i frfrenn / zznz / E / Yii 20°C. The five bolts prepared in this way, which had been subjected to the base treatment and the immersion treatment (aqueous solution containing 1% by mass of sodium silicate and 5% by mass of lubricant a; surface temperature of the bolts: 185°C to 220°C), were then subjected to a measurement of the surface coefficient of friction according to the ISO16047 HH method to calculate the average value of the coefficient of friction in the same way as Example 59. The average coefficient of friction was 0.154. The five bolts prepared in this manner, which had undergone the base treatment and the immersion treatment (aqueous solution containing 1% by mass of sodium silicate and 5% by mass of lubricant a; bolt surface temperature: 185°C to 220°C), were then subjected to a salt spray test in accordance with JIS Z-2371, and it was confirmed whether the bolts had rusted every 168 hours from the start of the test to evaluate corrosion resistance, in the same manner as Example 59. As a result, rust formation was not confirmed for the five bolts at 1176 hours from the start of the salt spray test.<Ejemplo 62> As a dip treatment agent, sodium silicate and a lubricant, “AQUACER 497” (product name) available from BYK Corporation (hereafter referred to as “lubricant b”) was dissolved and mixed in deionized water to include 1% by mass of sodium silicate and 3% by mass of lubricant b to prepare 1000 mL of an aqueous solution containing 1% by mass of sodium silicate and 3% by mass of lubricant b. Five bolts that had undergone the base treatment and the dip treatment were prepared in the same way as in Example 59, except that the dip treatment was carried out using 1000 mL of the aqueous solution containing 1% by mass of sodium silicate and 3% by mass of lubricant b at a solution temperature of 20°C instead of 1000 mL of the aqueous solution containing 1% by mass of sodium silicate at a solution temperature of 20°C.Note that lubricant b (“AQUACER 497” available from BYK Corporation) is an aqueous emulsion that includes a paraffin wax as a base. The five bolts prepared in this way, which had been subjected to the base treatment and the immersion treatment (aqueous solution containing 1% by mass of sodium silicate and 3% by mass of lubricant b; surface temperature of the bolts: 185°C to 220°C), were then subjected to a measurement of the surface coefficient of friction according to the ISO16047 HH method to calculate the coefficient of friction in the same way as Example 59. The average coefficient of friction was 0.111. The five bolts prepared in this manner, which had undergone the base treatment and the immersion treatment (aqueous solution containing 1% by mass of sodium silicate and 3% by mass of lubricant b; bolt surface temperature: 185°C to 220°C), were then subjected to a salt spray test in accordance with JIS Z-2371, and it was confirmed whether the bolts had rusted every 168 hours from the start of the test to evaluate corrosion resistance, in the same manner as Example 59. As a result, rust formation was not confirmed for the five bolts at 1008 hours from the start of the salt spray test. <Ejemplo 63> As a dip treatment agent, sodium silicate and a lubricant, “AQUACER 497” (product name) available from BYK Corporation (lubricant b) was dissolved and mixed in deionized water to include 1% by mass of sodium silicate and 5% by mass of lubricant b to prepare 1000 mL of an aqueous solution containing 1% by mass of sodium silicate and 5% by mass of lubricant b. Five bolts that had been subjected to the base treatment and the dip treatment were prepared the same as in Example 59, except that the dip treatment was carried out using 1000 mL of the aqueous solution containing 1% by mass of sodium silicate and 5% by mass of lubricant b at a solution temperature of 20°C instead of 1000 mL of the aqueous solution containing 1% by mass of sodium silicate at a solution temperature of 20°C. The five bolts prepared in this way, which had been subjected to the base treatment and the immersion treatment (aqueous solution containing 1% by mass of sodium silicate and 5% by mass of lubricant b; surface temperature of the bolts: 185°C to 220°C), were then subjected to a measurement of the surface coefficient of friction according to the ISO16047 HH method to calculate the coefficient of friction in the same way as Example 59. The average coefficient of friction was 0.098. The five bolts prepared in this manner, which had undergone the base treatment and the immersion treatment (aqueous solution containing 1% by mass of sodium silicate and 5% by mass of lubricant b; bolt surface temperature: 185°C to 220°C), were then subjected to a salt spray test in accordance with JIS Z-2371, and it was confirmed whether the bolts had rusted every 168 hours from the start of the test to evaluate corrosion resistance, in the same manner as Example 59. As a result, rust formation was not confirmed for the five bolts at 1008 hours from the start of the salt spray test.<Ejemplo 64> As a dip treatment agent, sodium silicate and lubricant, “AQUACER 1547” (product name) available from BYK Corporation (hereafter referred to as “lubricant c”) was dissolved and mixed in deionized water to thereby include 1% by mass of sodium silicate and 3% by mass of lubricant c to prepare 1000 mL of an aqueous solution containing 1% by mass of sodium silicate and 3% by mass of lubricant c. Five bolts that had undergone the base treatment and the dip treatment were prepared the same as in Example 59, except that the dip treatment was carried out using 1000 mL of the aqueous solution containing 1% by mass of sodium silicate and 3% by mass of lubricant c at a solution temperature of 20°C instead of 1000 mL of the aqueous solution containing 1% by mass of sodium silicate at a solution temperature of 20°C.Note that lubricant c (“AQUACER 1547 available from BYK Corporation”) is an aqueous emulsion that includes a modified polyethylene wax as a base. The five bolts prepared in this way, which had been subjected to the base treatment and the immersion treatment (aqueous solution containing 1% by mass of sodium silicate and 3% by mass of lubricant c; surface temperature of the bolts: 185°C to 220°C), were then subjected to a measurement of the surface coefficient of friction according to the ISO16047 HH method to calculate the coefficient of friction in the same way as Example 59. The average coefficient of friction was 0.120. The five bolts prepared in this manner, which had undergone the base treatment and the immersion treatment (aqueous solution containing 1% by mass of sodium silicate and 3% by mass of lubricant c; surface temperature of the bolts: 185°C to 220°C), were then subjected to a salt spray test in accordance with JIS Z-2371, and it was confirmed whether the bolts had rusted every 168 hours from the start of the test to evaluate corrosion resistance, in the same manner as Example 59. As a result, rust formation was not confirmed for the five bolts at 1008 hours from the start of the salt spray test.<Ejemplo 65> As a dip treatment agent, sodium silicate and a lubricant, “AQUACER 1547” (product name) available from BYK Corporation (the lubricant c) was dissolved and mixed in deionized water to include 1% by mass of sodium silicate and 5% by mass of lubricant c to prepare 1000 mL of an aqueous solution containing 1% by mass of sodium silicate and 5% by mass of lubricant c. Five bolts that had been subjected to the base treatment and the dip treatment were prepared in the same way as in Example 59, except that the dip treatment was carried out using 1000 mL of the aqueous solution containing 1% by mass of sodium silicate and 5% by mass of lubricant c at a solution temperature of 20°C instead of 1000 mL of the aqueous solution containing 1% by mass of sodium silicate at a solution temperature of 20°C. The five bolts prepared in this way, which had been subjected to the base treatment and the immersion treatment (aqueous solution containing 1% by mass of sodium silicate and 5% by mass of lubricant c; surface temperature of the bolts: 185°C to 220°C), were then subjected to a measurement of the surface coefficient of friction according to the ISO16047 HH method to calculate the coefficient of friction in the same way as Example 59. The average coefficient of friction was 0.105. The five bolts prepared in this manner, which had undergone the base treatment and the immersion treatment (aqueous solution containing 1% by mass of sodium silicate and 5% by mass of lubricant c; bolt surface temperature: 185°C to 220°C), were then subjected to a salt spray test in accordance with JIS Z-2371, and it was confirmed whether the bolts had rusted every 168 hours from the start of the test to evaluate corrosion resistance, in the same manner as Example 59. As a result, rust formation was not confirmed for the five bolts at 1008 hours from the start of the salt spray test. <Ejemplo 66> As a dip treatment agent, sodium silicate and lubricant, “LUBRON LDW-410” (product name) available from DAIKIN INDUSTRIES, LTD. (hereafter referred to as “lubricant d’j” was dissolved and mixed in deionized water to include 1% by mass of sodium silicate and 3% by mass of lubricant d to prepare 1000 mL of an aqueous solution containing 1% by mass of sodium silicate and 3% by mass of lubricant d. Five bolts that had undergone the base treatment and the dip treatment were prepared the same as in Example 59, except that the dip treatment was carried out using 1000 mL of the aqueous solution containing 1% by mass of sodium silicate and 3% by mass of lubricant d at a solution temperature of 20°C instead of 1000 mL of the aqueous solution containing 1% by mass of sodium silicate at a solution temperature of 20°C.Note that the lubricant d (“LUBRON LDW-410” available from DAIKIN INDUSTRIES, LTD.) is a dispersion liquid in which fine particles of low molecular weight fluororesin are dispersed in water. The five bolts prepared in this way, which had been subjected to the base treatment and the immersion treatment (aqueous solution containing 1% by mass of sodium silicate and 3% by mass of lubricant d; surface temperature of the bolts: 185°C to 220°C), were then subjected to a measurement of the surface coefficient of friction according to the ISO16047 HH method to calculate the coefficient of friction in the same way as Example 59. The average coefficient of friction was 0.166. The five bolts prepared in this manner, which had undergone the base treatment and the immersion treatment (aqueous solution containing 1% by mass of sodium silicate and 3% by mass of lubricant d; bolt surface temperature: 185°C to 220°C), were then subjected to a salt spray test in accordance with JIS Z-2371, and it was confirmed whether the bolts had rusted every 168 hours from the start of the test to evaluate corrosion resistance, in the same manner as Example 59. As a result, rust formation was not confirmed for the five bolts at 1008 hours from the start of the salt spray test. <Ejemplo 67> As a dip treatment agent, sodium silicate and a lubricant, “LUBRON LDW-410” (product name) available from DAIKIN INDUSTRIES, LTD. (the lubricant d) was dissolved and mixed in deionized water to include 1% by mass of sodium silicate and 5% by mass of lubricant d to prepare 1000 mL of an aqueous solution containing 1% by mass of sodium silicate and 5% by mass of lubricant d. Five bolts that had undergone the base treatment and the dip treatment were prepared in the same way as in Example 59, except that the dip treatment was carried out using 1000 mL of the aqueous solution containing 1% by mass of sodium silicate and 5% by mass of lubricant d at a solution temperature of 20°C instead of 1000 mL of the aqueous solution containing 1% by mass of sodium silicate at a solution temperature of 20°C. The five bolts prepared in this way, which had been subjected to the base treatment and the immersion treatment (aqueous solution containing 1% by mass of sodium silicate and 5% by mass of lubricant d; surface temperature of the bolts: 185°C to 220°C), were then subjected to a measurement of the surface coefficient of friction according to the ISO16047 HH method to calculate the coefficient of friction in the same way as Example 59. The average coefficient of friction was 0.173. The five bolts prepared in this manner, which had undergone the base treatment and the immersion treatment (aqueous solution containing 1% by mass of sodium silicate and 5% by mass of lubricant d; bolt surface temperature: 185°C to 220°C), were then subjected to a salt spray test in accordance with JIS Z-2371, and it was confirmed whether the bolts had rusted every 168 hours from the start of the test to evaluate corrosion resistance, in the same manner as Example 59. As a result, rust formation was not confirmed for the five bolts at 1008 hours from the start of the salt spray test. <Ejemplo 68> As a dip treatment agent, sodium silicate and a lubricant, “AQUACER 593” (product name) available from BYK Corporation (lubricant a) was dissolved and mixed in deionized water to include 1% by mass of sodium silicate and 3% by mass of the lubricant to prepare 1000 mL of an aqueous solution containing 1% by mass of sodium silicate and 3% by mass of lubricant a. Five bolts that had undergone the base treatment and the dip treatment were prepared the same as in Example 59, except that the dip treatment was carried out: using i frfrenn / zznz / E / Yii 1000 mL of the aqueous solution containing 1% by mass of sodium silicate and 3% by mass of the lubricant at a solution temperature of 20°C instead of 1000 mL of the aqueous solution containing 1% by mass of sodium silicate at a solution temperature of 20°C; and with the surface temperature of the bolts from 235°C to 270°C. The five bolts prepared in this way, which had been subjected to the base treatment and the immersion treatment (aqueous solution containing 1% by mass of sodium silicate and 3% by mass of lubricant a; surface temperature of the bolts: 235°C to 270°C), were then subjected to a measurement of the surface coefficient of friction according to the ISO16047 HH method to calculate the coefficient of friction in the same way as Example 59. The average coefficient of friction was 0.162. The five bolts prepared in this manner, which had undergone the base treatment and the immersion treatment (aqueous solution containing 1% by mass of sodium silicate and 3% by mass of lubricant a; bolt surface temperature: 235°C to 270°C), were then subjected to a salt spray test in accordance with JIS Z-2371, and it was confirmed whether the bolts had rusted every 168 hours from the start of the test to evaluate corrosion resistance, in the same manner as Example 59. As a result, rust formation was not confirmed for the five bolts at 1176 hours from the start of the salt spray test. <Ejemplo 69> As a dip treatment agent, sodium silicate and a lubricant, “AQUACER 593” (product name) available from BYK Corporation (the lubricant a) was dissolved and mixed in deionized water to include 1% by mass of sodium silicate and 3% by mass of the lubricant to prepare 1000 mL of an aqueous solution containing 1% by mass of sodium silicate and 3% by mass of lubricant a. Five bolts that had been subjected to the base treatment and the dip treatment were prepared the same as in Example 59, except that the dip treatment was carried out: using 1000 mL of the aqueous solution containing 1% by mass of sodium silicate and 3% by mass of lubricant a at a solution temperature of 20°C instead of 1000 mL of the aqueous solution containing 1% by mass of sodium silicate at a solution temperature of 20°C; and with the surface temperature of the bolts from 85°C to 120°C. The five bolts prepared in this way, which had been subjected to the base treatment and the immersion treatment (aqueous solution containing 1% by mass of sodium silicate and 3% by mass of lubricant a; surface temperature of the bolts: 85°C to 120°C), were then subjected to a measurement of the surface coefficient of friction according to the ISO16047 HH method to calculate the coefficient of friction in the same way as Example 59. The average coefficient of friction was 0.166. The five bolts prepared in this manner, which had been subjected to the i frfrenn / zznz / E / Yii base treatment and the immersion treatment (aqueous solution containing 1% by mass of sodium silicate and 3% by mass of lubricant a; bolt surface temperature: 85°C to 120°C), were then subjected to a salt spray test in accordance with JIS Z-2371, and it was confirmed whether the bolts had rusted every 168 hours from the start of the test to evaluate corrosion resistance, in the same manner as Example 59. As a result, rust formation was not confirmed for the five bolts at 672 hours from the start of the salt spray test. <Ejemplo Comparativo 15> Five bolts that had been subjected only to the base treatment were prepared the same as in Example 59, except that after the base treatment, the immersion treatment with the aqueous solution containing 1% by mass of sodium silicate was not carried out and the bolts were cooled to room temperature as they were. The five bolts prepared in this way, which had been subjected only to the base treatment, were then subjected to a measurement of the surface coefficient of friction according to the ISO16047 HH method to calculate the average value of the coefficient of friction in the same way as Example 59. The average coefficient of friction was 0.228. The five bolts prepared in this manner, which had undergone only the base treatment, were then subjected to a salt spray test in accordance with JIS Z-2371. Rust formation was confirmed every 168 hours from the start of the test to assess corrosion resistance, in the same manner as Example 59. As a result, rust formation was not confirmed for all five bolts at 168 hours from the start of the salt spray test, but rust formation was confirmed in two or more bolts at 336 hours from the start of the test. [Industrial Applicability] According to the present description, it is possible to readily impart improved corrosion resistance to a metal or alloy material. Furthermore, according to the present description, it is possible to provide an article that has superior corrosion resistance compared to that of the related art.

Claims

1. An anti-corrosion method, characterized in that it comprises: a step for treating an object to be treated, which contains a metal or an alloy or has on a surface a film or layer containing a metal or an alloy, and has been heated to a temperature above 180°C, with an aqueous solution containing an inorganic acid or an inorganic salt.

2. The anti-corrosion method according to claim 1, characterized in that the object to be treated has a temperature above 220°C when treated with the aqueous solution.

3. The anti-corrosion method according to claim 1 or 2, characterized in that the aqueous solution containing an inorganic acid or an inorganic salt is an aqueous solution containing at least one selected from silicic acid, silicate, phosphoric acid, phosphate, monohydrogen phosphate, dihydrogen phosphate, sulfuric acid, sulfate, nitric acid, nitrate, molybdenum acid, molybdate, and zirconium salt.

4. The anti-corrosion method according to any of claims 1 to 3, characterized in that the aqueous solution contains 0.1% by mass or more of an inorganic acid and / or an inorganic salt.

5. The anti-corrosion method according to any of claims 1 to 4, characterized in that the aqueous solution containing an inorganic acid or an inorganic salt further contains a lubricant.

6. The anti-corrosion method according to any of claims 1 to 5, characterized in that the aqueous solution containing an inorganic acid or an inorganic salt has a pH of 4 or more.

7. The anti-corrosion method according to any of claims 1 to 6, characterized in that it does not comprise: a step for heating the object to be treated to a temperature of 200°C or more after treating the object to be treated with the aqueous solution.

8. An anti-corrosion method, characterized in that it comprises: a step for treating an object to be treated, which contains a metal or an alloy or has on a surface a film or layer containing a metal or an alloy, with an aqueous solution containing at least one selected from silicic acid, silicate, phosphoric acid, phosphate, monohydrogen phosphate, dihydrogen phosphate, and zirconium salt.

9. The anti-corrosion method according to claim 8, characterized in that the aqueous solution containing an inorganic acid or an inorganic salt further contains a lubricant.

10. The anti-corrosion method according to claim 8 or 9, characterized in that it does not comprise: a step for heating the object to be treated to a temperature of 200°C or more after treating the object to be treated with the aqueous solution.

11. The anti-corrosion method according to any of claims 1 to 10, characterized in that the object to be treated contains at least one selected from zinc, zinc alloys, aluminum, aluminum alloys, iron, and iron alloys, or has on a surface a film or layer containing at least one selected from zinc, zinc alloys, aluminum, aluminum alloys, iron, and iron alloys.

12. An article, characterized in that it is treated with anti-corrosion by the anti-corrosion method, in accordance with any of claims 1 to 11.