Composition for black trivalent chromium conversion treatment and method for producing member provided with conversion coating film

Abstract

The conversion treatment composition according to one embodiment of the present invention contains a trivalent chromium-containing substance, an organic sulfur compound, an organic phosphonic acid compound, a vanadium-containing substance, and a hydroxycarboxylic acid-containing substance. This makes it possible to form a conversion coating having both a black appearance and a high corrosion resistance even when the cumulative treatment area is increased by quantitative replenishment management. The ratio in this conversion treatment composition between the molar concentration as vanadium of the vanadium-containing substance and the molar concentration as hydroxycarboxylic acid of the hydroxycarboxylic acid-containing substance may be 1 : 1 to 1 : 10.

Description

Trivalent chromium black chemical conversion coating composition and method for manufacturing a member having a chemical conversion coating

[0001] The present invention relates to a chemical conversion treatment composition that is substantially free of hexavalent chromium ions, which are harmful to the natural environment, i.e., is hexavalent chromium-free, is capable of forming a black coating containing trivalent chromium on the metal surface of a component, and has stable performance and a long bath life even when operated with fixed-quantity replenishment, and to a method for producing a component equipped with a chemical conversion coating formed from the chemical conversion treatment composition.

[0002] In recent years, environmental directives such as the RoHS (Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment) Directive and the ELV (End of Life Vehicles) Directive have required restrictions on the use of hazardous substances (such as lead, mercury, cadmium, and hexavalent chromium ions).

[0003] Following this trend, chromate coatings, which are effective as corrosion-preventive chemical conversion coatings for members having metal surfaces such as zinc-plated members, have come to be formed from chemical conversion treatment compositions containing trivalent chromium ions, rather than using chromates containing hexavalent chromium ions as compositions for forming chemical conversion coatings by chemical conversion treatment (in this specification, these compositions are referred to as "chemical conversion treatment compositions").

[0004] Among these chemical conversion treatment compositions, there are those that form chemical conversion coatings that have a black appearance (in this specification, these chemical conversion coatings are referred to as "black coatings"), and are widely used for components (press-molded products such as plates, housings, hinges, and panels) and parts (fastening parts such as bolts and nuts, and fasteners such as clamps and clips) for office equipment, electrical equipment, automobiles, etc. However, there are problems such as a decrease in the stability of the chemical conversion treatment composition, and an increase in the cumulative amount of treated area of ​​the components, etc. treated with the chemical conversion treatment composition (hereinafter abbreviated as "cumulative treated area"), which deteriorates the appearance of the black coating, i.e., the black appearance is not obtained and the coating turns gray.

[0005] To address the problem of decreased stability, a method of improving stability by adding two types of specific organic acids or salts thereof has been proposed, for example, in Patent Document 1. To address the deterioration of the appearance of the black coating due to an increase in the cumulative treatment area, a method of adding an organic sulfur compound and an organic phosphonic acid compound consisting of one or more compounds selected from the group consisting of organic phosphonic acids and their ions and salts has been proposed, for example, in Patent Document 2.

[0006] Patent No. 6532003 Patent No. 4840790

[0007] However, the inventors' investigations revealed that the method of adding two specific organic acids or their salts as in Patent Document 1 cannot achieve both high corrosion resistance and deterioration of appearance due to an increase in cumulative treatment area. It was also found that the method of adding organic sulfur compounds and organic phosphonic acid compounds as in Patent Document 2 preferably increases the amount of the compounds added as the cumulative treatment area increases in order to maintain a good black appearance and high corrosion resistance. In other words, it was revealed that the method of Patent Document 2 has room for improvement in terms of suitability for fixed-quantity replenishment management assuming continuous treatment.

[0008] Therefore, an object of the present invention is to provide a chemical conversion coating composition that can form a chemical conversion coating that has both a black appearance and high corrosion resistance even when the cumulative treatment area increases through quantitative replenishment management, and a method for manufacturing a member having such a chemical conversion coating.

[0009] The present inventors conducted extensive research to solve the above problems, and as a result, discovered that by incorporating a vanadium-containing substance and a hydroxycarboxylic acid-containing substance in a specific ratio, it is possible to obtain a chemical conversion coating composition that is capable of forming a chemical conversion coating that has both a black appearance and high corrosion resistance, even when the cumulative treatment area increases with constant supply management.

[0010] The present invention, which was obtained based on the above findings, provides, as one aspect thereof, a chemical conversion treatment composition containing a trivalent chromium-containing substance, an organic sulfur compound, an organic phosphonic acid compound, a vanadium-containing substance, and a hydroxycarboxylic acid-containing substance.

[0011] In the chemical conversion treatment composition, the ratio of the molar concentration of the vanadium-containing substance in terms of vanadium to the molar concentration of the hydroxycarboxylic acid-containing substance in terms of hydroxycarboxylic acid may be 1:1 to 1:10.

[0012] In the chemical conversion treatment composition, the content of the trivalent chromium-containing substance may be 1 to 10 g / L in terms of chromium, the content of the organic sulfur compound may be 0.1 to 10 g / L, and the content of the organic phosphonic acid compound may be 0.1 to 20 g / L.

[0013] The chemical conversion coating composition may contain one or more substances selected from the group consisting of nickel-containing substances and cobalt-containing substances.

[0014] The chemical conversion coating composition may contain a zinc-containing substance in an amount of 15 g / L or less in terms of zinc.

[0015] In another aspect, the present invention provides a method for producing a member having a chemical conversion coating, the method comprising contacting the above-mentioned chemical conversion treatment composition with a substrate having a surface made of a material containing zinc. It may be preferable that the chemical conversion treatment composition be managed by constant replenishment.

[0016] By using the chemical conversion coating composition according to the present invention, it is possible to stably form a black coating that is black in appearance and has excellent corrosion resistance, even when the cumulative treatment area increases through quantitative replenishment control. Therefore, compared to conventional techniques, the chemical conversion coating composition according to the present invention stabilizes quality with simpler control (quantitative replenishment), and can therefore greatly contribute to stabilizing quality in mass production.

[0017] A chemical conversion treatment composition according to one embodiment of the present invention contains a trivalent chromium-containing substance, an organic sulfur compound, an organic phosphonic acid compound, a vanadium-containing substance, and a hydroxycarboxylic acid-containing substance, in which the ratio of the vanadium-equivalent molar concentration of the vanadium-containing substance to the hydroxycarboxylic acid-equivalent molar concentration of the hydroxycarboxylic acid-containing substance is 1:1 to 1:10, and the composition is substantially free of hexavalent chromium ions, i.e., is a hexavalent chromium-free aqueous composition.

[0018] By bringing the chemical conversion coating composition according to this embodiment into contact with a member having a surface made of a metallic material such as zinc plating, a chemical conversion coating with a black appearance and high corrosion resistance is formed. Moreover, since the performance is unlikely to change even if the cumulative treated area increases due to the control of fixed-quantity replenishment, the quality can be stabilized with simple control (fixed-quantity replenishment).

[0019] Each component will be described in detail below. (1) Trivalent chromium-containing substance The chemical conversion treatment composition according to this embodiment comprises a trivalent chromium-containing substance. The trivalent chromium-containing substance is one or more selected from the group consisting of trivalent chromium and water-soluble substances containing it (e.g., trivalent chromium complexes). As a raw material for the trivalent chromium-containing substance, it is preferable to use a compound capable of generating a trivalent chromium-containing substance in water (hereinafter referred to as a "trivalent chromium compound").

[0020] Examples of trivalent chromium compounds include trivalent chromium salts such as chromium chloride, chromium sulfate, chromium nitrate, chromium phosphate, and chromium acetate, as well as compounds obtained by reducing hexavalent chromium compounds such as chromic acid and dichromate to trivalent chromium with a reducing agent. The trivalent chromium compound may be composed of only one type of compound, or may be composed of multiple types. Preferred examples of trivalent chromium compounds are chromium nitrate and chromium chloride. Note that, since a hexavalent chromium compound is not actively added as a raw material to the chemical conversion treatment composition of the present invention, the chemical conversion treatment composition of the present invention is substantially free of hexavalent chromium, i.e., is so-called hexavalent chromium-free.

[0021] The content of the trivalent chromium-containing substance is preferably 1 g / L or more in terms of chromium equivalent, from the viewpoint of stably forming a chemical conversion coating. The upper limit of the trivalent chromium-containing substance is not particularly limited, but from the viewpoint of appropriately ensuring the effect of the trivalent chromium-containing substance without increasing the burden on wastewater treatment, the upper limit is preferably about 10 g / L. Furthermore, from the viewpoint of ease of forming a chemical conversion coating, the content of the trivalent chromium-containing substance is preferably 2 to 5 g / L.

[0022] (2) Organic Sulfur Compound The chemical conversion coating composition according to this embodiment contains an organic sulfur compound, which is an organic compound containing sulfur as a constituent element. Examples of sulfur-containing functional groups contained in the organic sulfur compound include -SH (mercapto group), -S- (thioether group), >C=S (thioaldehyde group, thioketone group), -COSH (thiocarbosyl group), -SSH (dithiocarbosyl group), -CSNH2 (thioamide group), and -SCN (thiocyanate group, isothiocyanate group). Specific examples of organic sulfur compounds include ammonium thioglycolate, thioglycolic acid, thiomaleic acid, thioacetamide, dithioglycolic acid, ammonium dithioglycolate, ammonium dithiodiglycolate, dithiodiglycolic acid, cysteine, saccharin, thiamine nitrate, sodium N,N-diethyl-dithiocarbamate, 1,3-diethyl-2-thiourea, dipyridine, N-thiazole-2-sulfamylamide, 1,2,3-benzotriazole, 2-thiazoline-2-thiol, thiazole, thiourea, thiozole, sodium thioindoxylate, o-sulfonamidobenzoic acid, sulfanilic acid, orange-2, methyl orange, naphthionic acid, naphthalene-α- Examples include sulfonic acid, 2-mercaptobenzothiazole, 1-naphthol-4-sulfonic acid, Scheffer's acid, sulfadiazine, ammonium rhodanate, potassium rhodanate, sodium rhodanate, rhodanine, ammonium sulfide, sodium sulfide, ammonium sulfate, thioglycerin, thioacetic acid, potassium thioacetate, thiodiacetic acid, 3,3-thiodipropionic acid, and thiosemicarbazide.

[0023] Among these organic sulfur compounds, it is preferable to contain one or more selected from the group consisting of thioglycolic acid, dithiodiglycolic acid, and ions and salts thereof, in order to stably obtain a black coating.

[0024] The organic sulfur compound is considered to be one of the components that directly affects the blackening of the chemical conversion coating, and its content is preferably 0.1 to 10 g / L. If the content is less than 0.1 g / L, the blackening effect is weak, and even if it is added in excess of 10 g / L, the blackening effect saturates. From the viewpoint of stably forming a black coating while appropriately ensuring the effect of the organic sulfur compound, the content of the organic sulfur compound is more preferably 0.3 to 8 g / L, and particularly preferably 0.5 to 6 g / L.

[0025] (3) Organic Phosphonic Acid Compound The term "organic phosphonic acid compound" in this embodiment refers to a substance consisting of one or more compounds selected from the group consisting of organic phosphonic acids and their ions and salts. Here, "organic phosphonic acid" refers to a compound having the rational formula R-P(=O)(OH)2 (R is an organic group) in which an organic group is bonded to a phosphonic group. Examples of organic phosphonic acids include 1-hydroxyethylidene-1,1-diphosphonic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, amino(trimethylenephosphonic acid), ethylenediaminetetra(methylenephosphonic acid), and diethylenetriaminepenta(methylenephosphonic acid). Examples of salts of these organic phosphonic acids include 1-hydroxyethylidene-1,1-diphosphonic acid tetrasodium salt, 1-hydroxyethylidene-1,1-diphosphonic acid trisodium salt, ethylenediaminetetra(methylenephosphonic acid) pentasodium salt, and diethylenetriaminepenta(methylenephosphonic acid) hexasodium salt. In many cases, the sodium ions of these salts are dissociated in the chemical conversion treatment composition.

[0026] The content of the organic phosphonic acid compound is preferably 0.1 to 20 g / L. If the content is less than 0.1 g / L, the formation of the chemical conversion coating is likely to be insufficient, and if the content exceeds 20 g / L, the formation of the chemical conversion coating saturates. From the viewpoint of stably forming the chemical conversion coating while appropriately ensuring the effect of the organic phosphonic acid compound, the content of the organic phosphonic acid compound is more preferably 0.2 to 15 g / L, and particularly preferably 0.3 to 10 g / L.

[0027] (4) Vanadium-Containing Substance The chemical conversion coating composition according to this embodiment contains a vanadium-containing substance. The vanadium-containing substance is one or more selected from the group consisting of water-soluble substances containing vanadium, and includes vanadium ions and complexes thereof, as well as vanadium oxyacid ions such as vanadate ions. As a raw material for the vanadium-containing substance, it is preferable to use a compound capable of producing a vanadium-containing substance in water (hereinafter referred to as a "vanadium compound").

[0028] Examples of vanadium compounds include vanadium chloride, vanadium sulfate, vanadium oxide sulfate, sodium vanadate, potassium vanadate, vanadium(II) oxide, and vanadium(V) oxide. The vanadium compound may be composed of only one type of compound, or may be composed of multiple types of compounds.

[0029] The molar concentration of the vanadium-containing substance is preferably 0.001 mol / L or more and 1 mol / L or less, calculated as vanadium. If the molar concentration is less than 0.001 mol / L, it may be difficult to obtain a chemical conversion coating having a black appearance, and if it exceeds 1 mol / L, the stability of the chemical conversion treatment composition may tend to decrease. From the viewpoint of obtaining a good chemical conversion coating while ensuring the stability of the chemical conversion treatment composition, the molar concentration of the vanadium-containing substance calculated as vanadium may more preferably be 0.002 to 0.5 mol / L, and may particularly preferably be 0.005 to 0.1 mol / L.

[0030] (5) Hydroxycarboxylic Acid-Containing Substance The chemical conversion treatment composition according to this embodiment contains a hydroxycarboxylic acid-containing substance. In this specification, the hydroxycarboxylic acid-containing substance is one or more substances selected from the group consisting of hydroxycarboxylic acids, which are carboxylic acids having a hydroxyl group, and water-soluble substances containing substances based thereon. As a raw material for the hydroxycarboxylic acid-containing substance, it is preferable to use a water-soluble compound that can dissolve in water to produce the hydroxycarboxylic acid-containing substance (hereinafter referred to as a "water-soluble hydroxycarboxylic acid compound"). The water-soluble hydroxycarboxylic acid compound also includes esters that produce hydroxycarboxylic acids upon hydrolysis.

[0031] Examples of hydroxycarboxylic acids include, but are not limited to, monohydroxymonocarboxylic acids such as glycolic acid and lactic acid, monohydroxypolycarboxylic acids such as malic acid and citric acid, polyhydroxymonocarboxylic acids such as ascorbic acid, and polyhydroxypolycarboxylic acids such as tartaric acid. Water-soluble hydroxycarboxylic acid compounds also include salts and ions of these hydroxycarboxylic acids, such as sodium salts and potassium salts.

[0032] The molar concentration of the hydroxycarboxylic acid-containing substance is preferably 0.001 mol / L or more and 5 mol / L or less, calculated as hydroxycarboxylic acid. If the molar concentration is less than 0.001 mol / L, the stability of the chemical conversion treatment composition may tend to decrease, while if it exceeds 5 mol / L, the load when treating the chemical conversion treatment composition as wastewater may increase. From the viewpoint of appropriately ensuring the stability and wastewater treatability of the chemical conversion treatment composition, the molar concentration of the hydroxycarboxylic acid-containing substance calculated as hydroxycarboxylic acid may more preferably be 0.002 to 5 mol / L, and particularly preferably be 0.005 to 1 mol / L.

[0033] In the chemical conversion treatment composition according to this embodiment, the ratio of the vanadium-equivalent molar concentration of the vanadium-containing substance to the hydroxycarboxylic acid-equivalent molar concentration of the hydroxycarboxylic acid-containing substance is 1: 1 to 1: 10. By adjusting the molar concentrations of the vanadium-containing substance and the hydroxycarboxylic acid-containing substance within the above ranges, a chemical conversion coating having a black appearance and high corrosion resistance can be stably obtained even if the cumulative treatment area is large.

[0034] (6) Nickel-containing substance, cobalt-containing substance The chemical conversion coating composition according to this embodiment may contain one or more substances selected from the group consisting of nickel-containing substances and cobalt-containing substances. The nickel-containing substance is one or more substances selected from the group consisting of water-soluble substances containing nickel, including nickel ions and complexes thereof. The cobalt-containing substance is one or more substances selected from the group consisting of water-soluble substances containing cobalt, including cobalt ions and complexes thereof. The nickel-containing substance contributes to blackening, and the cobalt-containing substance contributes to improving corrosion resistance. As raw materials for the nickel-containing substance and the cobalt-containing substance, it is desirable to use compounds (nickel compounds, cobalt compounds) capable of producing the nickel-containing substance and the cobalt-containing substance in water.

[0035] Examples of nickel compounds include nickel chloride, nickel sulfate, nickel nitrate, nickel phosphate, nickel acetate, etc., and the nickel compound may consist of only one compound or multiple compounds. Examples of cobalt compounds include cobalt chloride, cobalt sulfate, cobalt nitrate, cobalt phosphate, cobalt acetate, etc., and the cobalt compound may consist of only one compound or multiple compounds.

[0036] When a nickel-containing substance is contained, its content is preferably 0.05 to 5 g / L in terms of nickel. If its content is less than 0.05 g / L, the effect of improving blackening may be difficult to obtain, and if it exceeds 5 g / L, corrosion resistance may be reduced. From the viewpoint of stably obtaining the blackening effect while suppressing the influence on corrosion resistance, it may be preferable that the content of the nickel-containing substance be 0.1 to 3 g / L in terms of nickel. When a cobalt-containing substance is contained, its content is preferably 0.05 to 5 g / L in terms of cobalt. If its content is less than 0.05 g / L, the effect of improving corrosion resistance may be difficult to obtain, and if it exceeds 5 g / L, corrosion resistance may actually be reduced. From the viewpoint of stably obtaining the effect of improving corrosion resistance, it may be preferable that the content of the cobalt-containing substance be 0.1 to 3 g / L in terms of cobalt.

[0037] (7) Other Components In addition to the above substances, the chemical conversion coating composition according to this embodiment may contain one or more components selected from the group consisting of metal ions, inorganic acids and their anions, inorganic colloids, silane coupling agents, nitrogen compounds, and fluorine compounds. It may also contain one or more components selected from the group consisting of polymers such as waxes, corrosion inhibitors, surfactants, plastic dispersants, color formers such as dyes and pigments, desiccants, and dispersants. A reducing substance may also be added simultaneously.

[0038] Examples of metal ions include ions of Na, K, Ag, Au, Ru, Nb, Ta, Pt, Pd, Fe, Ca, Mg, Zr, Sc, Ti, Mn, Cu, Zn, Sn, Y, Mo, Hf, Te, and W, and these may exist in the form of oxyacid ions. When the member (substrate) to be chemically treated has a surface made of a zinc-containing material, zinc-containing substances (specifically, zinc ions and their complexes) that are water-soluble substances containing zinc accumulate in the chemical conversion treatment composition as the cumulative treatment area increases. Generally, as the zinc-equivalent concentration of the zinc-containing substance in the chemical conversion treatment composition increases, it becomes difficult to maintain the black appearance of the chemical conversion coating. However, the chemical conversion treatment composition according to this embodiment can obtain a black appearance even when the zinc-equivalent content of the zinc-containing substance is 15 g / L, and therefore may contain the zinc-containing substance within this range (15 g / L or less).

[0039] Examples of inorganic acids include hydrohalic acids such as hydrochloric acid, hydrofluoric acid, and hydrobromic acid, chloric acid, perchloric acid, chlorous acid, hypochlorous acid, sulfuric acid, sulfurous acid, nitric acid, and nitrous acid, and may also contain inorganic acids containing phosphorus such as phosphoric acid (orthophosphoric acid), polyphosphoric acid, metaphosphoric acid, pyrophosphoric acid, ultraphosphoric acid, hypophosphorous acid, and superphosphoric acid. The inorganic acid may be contained in the chemical conversion treatment composition as an ion.

[0040] The molar concentration of these inorganic acids and / or their ions in the chemical conversion treatment composition is not particularly limited. The ratio of the total molar concentration of the inorganic acids and their ions to the total molar concentration of trivalent chromium ions and the above metal ions (ions including vanadium, nickel ions, cobalt ions, etc.) may preferably be 0.1 to 10, and more preferably 0.5 to 3.

[0041] Examples of inorganic colloids include silica sol, alumina sol, titanium sol, and zirconia sol, and examples of silane coupling agents include organic silane coupling agents such as vinyltriethoxysilane.

[0042] Examples of the nitrogen compound include organic nitrogen compounds such as heterocyclic compounds, ureas, aliphatic amines, acid amides, aminocarboxylic acids, ammonium salt urea, amines, and nitrobenzenesulfonic acid, as well as nitrogen compounds such as urea, ammonium salts, and nitrates, and the preferred content of each of these compounds is 0.5 to 50 g / L.

[0043] (8) Solvent The solvent of the chemical conversion treatment composition according to this embodiment is mainly water, and from the viewpoint of stabilizing the contained components, a water-soluble organic solvent such as alcohol, ether, ester, etc. may be mixed in. The ratio of the organic solvent to the total solvent is not particularly limited, but from the viewpoint of ensuring appropriate wastewater treatability, it may be preferable to set it to 10 mass % or less.

[0044] (9) pH The pH of the chemical conversion treatment composition according to this embodiment is not particularly limited as long as it is acidic, but is preferably in the range of pH 1 to 4, and from the viewpoint of the stability of the chemical conversion treatment composition, particularly preferably pH 2 to 3. The pH may be adjusted using an alkaline substance such as sodium hydroxide, sodium bicarbonate, or ammonia, or an acidic substance such as hydrochloric acid, nitric acid, or sulfuric acid.

[0045] (10) Overcoat: After chemical conversion treatment using the chemical conversion treatment composition according to this embodiment, rinsing with water and applying an inorganic, organic, or organic-inorganic composite coating before or after drying further improves corrosion resistance. Examples of inorganic overcoats include silica-based and phosphate-based overcoats, but other overcoats are also possible. Examples of organic overcoats include paints and resins, and both aqueous and non-aqueous overcoats can be used. Examples of organic overcoats include, but are not limited to, organic coatings such as polyethylene, polyvinyl chloride, polystyrene, polypropylene, acrylic resin, methacrylic resin, polycarbonate, polyamide, polyacetal, fluororesin, urea resin, phenolic resin, unsaturated polyester resin, polyurethane, alkyd resin, epoxy resin, and melamine resin. The overcoat can be applied immediately after drying after chemical conversion treatment or after secondary processing such as bending. There are no limitations on the number of overcoats. The overcoat method is also not particularly limited, and various methods are possible, including paint application, dip coating, electrostatic coating, electrodeposition coating, and powder coating.

[0046] (11) Substrate There are no material limitations on the member (substrate) to be chemically treated, as long as the chemical conversion treatment using the chemical conversion treatment composition according to this embodiment proceeds appropriately. An example of a substrate is a substrate having a surface made of a material containing zinc, and a specific example of such a substrate is a member made of an iron-based material that has been plated with zinc or a zinc alloy. Even with such a substrate, as described above, the chemical conversion treatment composition according to this embodiment can perform chemical conversion treatment appropriately over a long period of time.

[0047] The effects of the present invention will be described below based on examples, but the present invention is not limited thereto. Chemical conversion treatments were performed using a chemical conversion treatment composition containing an organic sulfur compound and capable of forming a black coating, which contained a phosphorus-containing compound including an organic phosphonic acid compound, and in which the ratio of the vanadium-equivalent molar concentration of the vanadium-containing substance to the hydroxycarboxylic acid-equivalent molar concentration of the hydroxycarboxylic acid-containing substance was in the range of 1:0.5 to 1:10. The chemical conversion treatment composition was replenished in a fixed amount, and changes in the appearance and corrosion resistance of the black coating were observed as the cumulative treatment area increased. Note that all of the chemical conversion treatment compositions used in the examples were so-called hexavalent chromium-free compositions, which are essentially free of hexavalent chromium.

[0048] (1) Preparation of Chemical Conversion Treatment Compositions First, chemical conversion treatment compositions having the compositions shown in Tables 1 to 3 were prepared. The pH was adjusted to 2.4 using hydrochloric acid and sodium hydroxide. The chromium, nickel, and cobalt values ​​in the tables represent the chromium-equivalent content of the chromium-containing substance, the nickel-equivalent content of the nickel-containing substance, and the cobalt-equivalent content of the cobalt-containing substance in the chemical conversion treatment composition, respectively.

[0049] Chemical conversion treatment compositions having the compositions disclosed in Patent Document 1 were prepared as comparative examples (Examples 19 to 26) and Table 4 show chemical conversion treatment compositions having the compositions disclosed in Patent Document 2 were prepared as comparative examples (Examples 27 and 28). The content of the transition metals (nickel, vanadium, manganese) used in the chemical conversion treatment compositions of Examples 20 to 27 was 5 g / L, which is the median value of the range of 0.1 to 10 g / L that is considered to be a more preferred addition amount as described in Patent Document 1.

[0050]

[0051]

[0052]

[0053]

[0054]

[0055] (2) Preparation of Test Members Next, the bolts that had been electrogalvanized according to a conventional method were washed with water and then immersed in nitric acid (a 3 mL / L solution of 67.5% nitric acid, at room temperature (25°C), for 10 seconds) to activate the surface. This test member (substrate) was further washed with water at room temperature for 10 seconds, and then immersed for 45 seconds in a chemical conversion treatment composition having the composition shown in Tables 1 to 3 and maintained at pH 2.4 and 35°C. The test member was removed from the chemical conversion treatment composition, washed with water (room temperature, 10 seconds), and then dried at 80±5°C for 10 minutes.

[0056] In Examples 19 to 26 (Comparative Examples) shown in Table 4, the test members were immersed for 30 seconds in the chemical conversion treatment compositions maintained at pH 2.0 and 30° C., and in Examples 27 and 28 (Comparative Examples) shown in Table 5, the test members were immersed for 45 seconds in the chemical conversion treatment compositions maintained at pH 2.2 and 35° C. The test members were removed from the chemical conversion treatment compositions, washed with water (at room temperature for 10 seconds), and then dried at 80±5° C. for 10 minutes.

[0057] The surface treatment including the above chemical conversion treatment was carried out on a large number of bolts, and the components obtained by the first chemical conversion treatment immediately after the bath preparation, with cumulative treatment areas per 1 L of 250, 500, 750, and 1000 dm 2 The test member obtained by the chemical conversion treatment when the cumulative treatment area per 1 L was 500 dm2 was used as the test member for evaluation. 2 When this occurs, the zinc ion concentration contained in the chemical conversion treatment composition is approximately 8 g / L, and the cumulative treatment area per 1 L is 1000 dm 2 When this occurred, the zinc ion concentration contained in the chemical conversion treatment composition was approximately 15 g / L.

[0058] (3) Replenishment method As the chemical conversion treatment progresses, the components of the chemical conversion treatment composition decrease. 2 The amount of water to be replenished was determined as follows: First, when the treatment area was 100 dm per 1 L, 2At the time of reaching the target, the chemical conversion treatment composition was sampled, and the chromium concentration was calculated using an ICP optical emission spectrometer (ARCOS FH522 manufactured by Spectro Inc.) to determine the amount of chromium reduction in the sample. The amount of reduction in the chemical conversion treatment composition was calculated by determining that each component of the chemical conversion treatment composition had decreased at the same rate as this amount of chromium reduction. As a specific example, when the treatment area per 1 L was 100 dm 2 When the amount of chromium loss in the sample when the amount of chromium was increased was 10% by mass, it was determined that each component of the chemical conversion treatment composition had decreased by 10% by mass, and a composition having 1 / 10 the amount of the chemical conversion treatment composition at the time of bath preparation was replenished.

[0059] (4) Evaluation Method The color tone was judged visually, and the corrosion resistance was evaluated by a salt spray test in accordance with JIS Z 2371. The presence or absence of white rust was confirmed visually every 24 hours, and when the visual white rust area ratio reached 5% of the total, the cumulative salt spray time of the test member was taken as the white rust occurrence time and used as an index of corrosion resistance.

[0060] The evaluation results are shown in Tables 6 and 7. The columns show the appearance and corrosion resistance for the cumulative treatment area per liter. As a specific example, if the time it took for 5% white rust to appear was 96 hours and the appearance at this time was black, this is shown as "black / 96 hours."

[0061]

[0062]

Claims

1. A chemical conversion treatment composition comprising a trivalent chromium-containing substance, an organic sulfur compound, an organic phosphonic acid compound, a vanadium-containing substance, and a hydroxycarboxylic acid-containing substance.

2. The chemical conversion treatment composition according to claim 1, wherein the ratio of the vanadium-equivalent molar concentration of the vanadium-containing substance to the hydroxycarboxylic acid-equivalent molar concentration of the hydroxycarboxylic acid-containing substance is 1:1 to 1:

10.

3. The chemical conversion treatment composition according to claim 1 or 2, wherein the content of the trivalent chromium-containing substance is 1 to 10 g / L calculated as chromium, the content of the organic sulfur compound is 0.1 to 10 g / L, and the content of the organic phosphonic acid compound is 0.1 to 20 g / L.

4. The chemical conversion coating composition according to claim 1 or 2, which contains at least one substance selected from the group consisting of nickel-containing substances and cobalt-containing substances.

5. The chemical conversion treatment composition according to claim 1 or 2, which contains a zinc-containing substance in an amount of 15 g / L or less calculated as zinc.

6. A method for producing a member having a chemical conversion coating, comprising contacting a chemical conversion treatment composition according to claim 1 or 2 with a substrate having a surface made of a material containing zinc.

7. The method according to claim 6, wherein the chemical conversion treatment composition is managed by constant supply.

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