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

Abstract

Composition for chemical conversion treatment according to an aspect 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, and can therefore form a chemical conversion coating film that combines a black appearance and high corrosion resistance even when the cumulative treated area increases through fixed-quantity replenishment management. The composition for chemical conversion treatment may have a 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 of 1:1 to 1:10.

Description

TECHNICAL FIELD

[0001] The present invention relates to a composition for chemical conversion treatment that substantially does not contain hexavalent chromium ions, which are harmful to the natural environment, i.e., is hexavalent chromium-free, is capable of forming a black coating film containing trivalent chromium on the metal surface of a member, and has stable performance and a long bath life even when operated under fixed-quantity replenishment management, and relates also to a method for producing a member provided with a chemical conversion coating film formed using the composition for chemical conversion treatment.BACKGROUND ART

[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] In response to this trend, chromate coating films, which are effective as corrosion-protective chemical conversion coating films for members with metal surfaces such as zinc-plated members, are increasingly being formed using, as a composition for forming a chemical conversion coating film by chemical conversion treatment (this composition will be referred to as a "composition for chemical conversion treatment" in the present specification), a composition for chemical conversion treatment containing trivalent chromium ions rather than using a chromate containing hexavalent chromium ions.

[0004] Some of these compositions for chemical conversion treatment form chemical conversion coating films with a black appearance (these chemical conversion coating films will be referred to as "black coating films" in the present specification). They are widely used on members (press-formed products such as plates, housings, hinges, and panels) and parts (fasteners such as bolts and nuts, attachments such as clamps and clips, etc.) for office equipment, electrical equipment, and automobiles. However, problems have arisen in that the stability of these compositions for chemical conversion treatment deteriorates, as well as in that the appearance of the black coating film deteriorates as the cumulative amount of the treated area of members or the like treated with the composition for chemical conversion treatment (simply referred to as a "cumulative treated area," hereinafter) increases, that is, the black appearance is no longer achieved and the coating film turns gray.

[0005] To address the problem of deterioration in the stability, a method has been proposed in which the stability is improved by adding two types of specific organic acids or their salts, for example, as in Patent Document 1. To address the deterioration in appearance of the black coating film due to an increase in the cumulative treated area, a method has been proposed, as in Patent Document 2, in which an organic sulfur compound and an organic phosphonic acid compound composed of one or more compounds selected from the group consisting of organic phosphonic acids and their ions and salts are added.PRIOR ART DOCUMENTS[Patent documents]

[0006] [Patent Document 1] JP6532003B [Patent Document 2] JP4840790B OBJECT AND SUMMARY OF THE INVENTION

[0007] However, the inventors' investigations have revealed that the method of adding two specific organic acids or their salts, as in Patent Document 1, fails to achieve both the high corrosion resistance and the deterioration in appearance due to an increase in the cumulative treated area. It has also been found that the method of adding an organic sulfur compound and an organic phosphonic acid compound, as in Patent Document 2, preferably increases the amount of the above compounds added as the cumulative treated area increases in order to maintain a good black appearance and high corrosion resistance. In other words, it has been revealed that the method of Patent Document 2 leaves room for improvement from the viewpoint of its suitability for fixed-quantity replenishment management, which assumes continuous treatment.

[0008] In this context, a problem to be solved by the present invention is to provide a composition for chemical conversion treatment that can form a chemical conversion coating film that achieves both the black appearance and the high corrosion resistance even when the cumulative treated area increases with fixed-quantity replenishment, and a method for producing a member provided with such a chemical conversion coating film.

[0009] The inventors have conducted extensive research to solve the above problem. As a result, a knowledge has been obtained that by containing a vanadium-containing substance and a hydroxycarboxylic acid-containing substance in a specific ratio, a composition for chemical conversion treatment can be obtained that is capable of forming a chemical conversion coating film in which both the black appearance and the high corrosion resistance are achieved even when the cumulative treated area is increased through fixed-quantity replenishment management.

[0010] An aspect of the present invention obtained based on the above knowledge provides a composition for chemical conversion treatment 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.

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

[0012] In the above composition for chemical conversion treatment, the content of the trivalent chromium-containing substance may be 1 to 10 g / L in terms of chromium equivalent, 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 above composition for chemical conversion treatment may contain one or more substances selected from a group consisting of nickel-containing substances and cobalt-containing substances.

[0014] The above composition for chemical conversion treatment may contain a zinc-containing substance of a content of 15 g / L or less in terms of zinc equivalent.

[0015] Another aspect of the present invention provides a production method for a member provided with a chemical conversion coating film, the method comprising contacting the above composition for chemical conversion treatment with a base material having a surface of a material containing zinc. The composition for chemical conversion treatment may be preferably managed by fixed-quantity replenishment.

[0016] Using the composition for chemical conversion treatment according to the above invention, even when the cumulative treated area increases through fixed-quantity replenishment management, it is possible to consistently form a black coating film that is black in appearance and has excellent corrosion resistance. Therefore, compared to conventional techniques, the composition for chemical conversion treatment according to the present invention stabilizes the quality with simpler management (fixed-quantity replenishment), and it can thus contribute to stabilizing the quality in mass production.BEST MODE FOR CARRYING OUT THE INVENTION

[0017] The composition for chemical conversion treatment according to an 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. 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. The composition for chemical conversion treatment substantially does not contain hexavalent chromium ions, that is, it is a hexavalent chromium-free aqueous composition.

[0018] By carrying out a process of contacting the composition for chemical conversion treatment according to the present embodiment with a member having a surface made of a metal material such as zinc plating, a chemical conversion coating film having a black appearance and high corrosion resistance is formed. Furthermore, since its performance is unlikely to change even when the cumulative treated area increases with fixed-quantity replenishment management, the quality can be stabilized with simple management (fixed-quantity replenishment).

[0019] Each component will be described in detail below.(1) Trivalent Chromium-Containing Substance

[0020] The composition for chemical conversion treatment according to the present embodiment contains a trivalent chromium-containing substance. The trivalent chromium-containing substance is composed of one or more substances selected from the group consisting of trivalent chromium and a water-soluble substance containing trivalent chromium (e.g., trivalent chromium complexes). It is preferred to use a compound capable of generating a trivalent chromium-containing substance in water (referred to as a "trivalent chromium compound," hereinafter) as the raw material for the trivalent chromium-containing substance.

[0021] 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 ones with a reducing agent. The trivalent chromium compound may be composed of only one compound or two or more types. Preferred examples of trivalent chromium compounds are chromium nitrate and chromium chloride. The composition for chemical conversion treatment according to the present invention is substantially free of hexavalent chromium, or so-called hexavalent chromium-free, because hexavalent chromium compounds are not actively added as raw materials to the composition for chemical conversion treatment according to the present invention.

[0022] The content of the trivalent chromium-containing substance is preferably 1 g / L or more in terms of chromium equivalent from the perspective of stably forming a chemical conversion coating film. The upper limit of the trivalent chromium-containing substance content is not particularly limited, but a preferred upper limit is approximately 10 g / L from the perspective of appropriately ensuring the effects of containing the trivalent chromium-containing substance without increasing the burden on wastewater treatment. Furthermore, from the perspective of ease of forming a chemical conversion coating film, the content of the trivalent chromium-containing substance is preferably 2 to 5 g / L.(2) Organic Sulfur Compound

[0023] The composition for chemical conversion treatment according to the present embodiment contains an organic sulfur compound, which is an organic compound containing sulfur as its 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), -CSSH (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-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.

[0024] Among these organic sulfur compounds, it is preferred to include one or more selected from the group consisting of thioglycolic acid, dithiodiglycolic acid, and their ions and salts in order to consistently obtain a black coating film.

[0025] Organic sulfur compounds are considered to be one of the components that directly affect the blackening of the chemical conversion coating film, and the content is preferably 0.1 to 10 g / L. At a content of less than 0.1 g / L, the blackening effect is weak, and even at additions exceeding 10 g / L, the blackening effect saturates. From the perspective of stably forming a black coating film while adequately ensuring the effects of containing 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.(3) Organic Phosphonic Acid Compound

[0026] The "organic phosphonic acid compound" according to the present embodiment means a substance composed of one or more selected from the group consisting of organic phosphonic acids and their ions and salts. Here, the "organic phosphonic acid" refers to a compound having the rational formula R-P(=O)(OH) 2 (where 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 these salts, the sodium ion is often dissociated in the composition for chemical conversion treatment.

[0027] 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 film tends to be insufficient, while even if the content exceeds 20 g / L, the formation of the chemical conversion coating film saturates. From the perspective of stably forming a chemical conversion coating film while appropriately ensuring the effects 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.(4) Vanadium-Containing Substance

[0028] The composition for chemical conversion treatment according to the present embodiment contains a vanadium-containing substance. The vanadium-containing substance is composed of one or more substances selected from the group consisting of water-soluble substances containing vanadium, including vanadium ions and their complexes, as well as vanadium oxyacid ions such as vanadate ions. It is preferred to use a compound capable of generating a vanadium-containing substance in water (referred to as a "vanadium compound," hereinafter) as the raw material for the vanadium-containing substance.

[0029] 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 also be two or more types.

[0030] The molar concentration of the vanadium-containing substance is preferably 0.001 mol / L or more and 1 mol / L or less in terms of vanadium equivalent. If the above molar concentration is less than 0.001 mol / L, it may be difficult to obtain a chemical conversion coating film with a black appearance, while if it exceeds 1 mol / L, the stability of the composition for chemical conversion treatment may tend to decrease. From the perspective of obtaining a good chemical conversion coating while maintaining the stability of the composition for chemical conversion treatment, it may be more preferred for the vanadium-equivalent molar concentration of the vanadium-containing substance to be 0.002 to 0.5 mol / L and particularly preferably 0.005 to 0.1 mol / L.(5) Hydroxycarboxylic Acid-Containing Substance

[0031] The composition for chemical conversion treatment according to the present embodiment contains a hydroxycarboxylic acid-containing substance. In the present specification, the hydroxycarboxylic acid-containing substance is composed of one or more substances selected from the group consisting of water-soluble substances containing hydroxycarboxylic acids, which are carboxylic acids having a hydroxyl group, and substances based thereon. It is preferred to use a water-soluble compound capable of being dissolved in water to generate the hydroxycarboxylic acid-containing substance as the raw material for the hydroxycarboxylic acid-containing substance (the water-soluble compound is referred to as a "water-soluble hydroxycarboxylic acid compound," hereinafter). Water-soluble hydroxycarboxylic acid compounds also include esters that generate hydroxycarboxylic acids upon hydrolysis.

[0032] 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 and potassium salts.

[0033] The molar concentration of the hydroxycarboxylic acid-containing substance is preferably 0.001 mol / L or more and 5 mol / L or less in terms of hydroxycarboxylic acid equivalent. If the above molar concentration is less than 0.001 mol / L, the stability of the composition for chemical conversion treatment may tend to deteriorate, while if the above molar concentration exceeds 5 mol / L, the load during wastewater treatment of the composition for chemical conversion treatment may increase. From the perspective of ensuring the stability and wastewater treatability of the composition for chemical conversion treatment, the hydroxycarboxylic acid-equivalent molar concentration of the hydroxycarboxylic acid-containing substance may be preferably 0.002 to 5 mol / L and particularly preferably 0.005 to 1 mol / L.

[0034] In the composition for chemical conversion treatment according to the present 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 range, a chemical conversion coating film having a black appearance and high corrosion resistance can be consistently obtained even when the cumulative treated area is large.(6) Nickel-Containing Substance and Cobalt-Containing Substance

[0035] The composition for chemical conversion treatment according to the present 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 composed of one or more substances selected from the group consisting of water-soluble substances containing nickel, including nickel ions and their complexes. The cobalt-containing substance is composed of one or more substances selected from the group consisting of water-soluble substances containing cobalt, including cobalt ions and their complexes. The nickel-containing substance contributes to blackening, while the cobalt-containing substance contributes to improvement of corrosion resistance. It is desirable to use compounds (nickel compounds, cobalt compounds) capable of generating the nickel-containing substance and cobalt-containing substance in water as raw materials for the nickel-containing substance and cobalt-containing substance.

[0036] Examples of nickel compounds include nickel chloride, nickel sulfate, nickel nitrate, nickel phosphate, and nickel acetate. The nickel compound may be composed only of one type of compound or may also be composed of two or more types. Examples of cobalt compounds include cobalt chloride, cobalt sulfate, cobalt nitrate, cobalt phosphate, and cobalt acetate. The cobalt compound may be composed only of one type of compound or may also be composed of two or more types.

[0037] When a nickel-containing substance is contained, its content is preferably 0.05 to 5 g / L in terms of nickel equivalent. If its content is less than 0.05 g / L, the effect of improving blackening may be difficult to achieve, while if it exceeds 5 g / L, corrosion resistance may decrease. From the perspective of consistently achieving the blackening effect while minimizing the impact on corrosion resistance, it may be preferred for the nickel-containing substance content to be 0.1 to 3 g / L in terms of nickel equivalent. When a cobalt-containing substance is contained, its content is preferably 0.05 to 5 g / L in terms of cobalt equivalent. If its content is less than 0.05 g / L, the effect of improving corrosion resistance may be difficult to achieve, while if it exceeds 5 g / L, corrosion resistance may rather decrease. From the perspective of consistently achieving the effect of improving corrosion resistance, it may be preferred for the cobalt-containing substance content to be 0.1 to 3 g / L in terms of cobalt equivalent.(7) Other Components

[0038] In addition to the above substances, the composition for chemical conversion treatment according to the present embodiment may contain one or more substances 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 substances selected from the group consisting of polymers such as wax, corrosion inhibitors, surfactants, plastic dispersants, color formers such as dyes and pigments, desiccants, and dispersants. A reducing substance may also be added simultaneously.

[0039] 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 ions may exist in the form of oxyacid ions. When the member (base material) to be subjected to chemical conversion treatment has a surface of a material containing zinc, zinc-containing substances (specifically, zinc ions and their complexes) accumulate in the composition for chemical conversion treatment as the cumulative treated area increases. In general, as the zinc-equivalent concentration of the zinc-containing substance in the composition for chemical conversion treatment increases, it becomes difficult to maintain the black appearance of the chemical conversion coating film. Fortunately, however, the composition for chemical conversion treatment according to the present embodiment can achieve a black appearance even with a zinc-equivalent content of 15 g / L of this zinc-containing substance, so the zinc-containing substance may be contained within this range (15 g / L or less).

[0040] 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. Phosphorus-containing inorganic acids such as phosphoric acid (orthophosphoric acid), polyphosphoric acid, metaphosphoric acid, pyrophosphoric acid, ultraphosphoric acid, hypophosphorous acid, and superphosphoric acid may also be contained. The inorganic acids may be contained in the composition for chemical conversion treatment as ions.

[0041] The molar concentration of these inorganic acids and / or their ions in the composition for chemical conversion treatment is not particularly limited. The total molar concentration of the inorganic acids and their ions, expressed as a ratio to the total molar concentration of trivalent chromium ions and the above metal ions (such as vanadium-containing ions, nickel ions, and cobalt ions), may preferably be 0.1 to 10 and more preferably 0.5 to 3.

[0042] Examples of inorganic colloids include silica sol, alumina sol, titanium sol, and zirconia sol. Examples of silane coupling agents include organic silane coupling agents such as vinyltriethoxysilane.

[0043] Examples of nitrogen compounds include organic nitrogen compounds such as heterocyclic compounds, ureas, aliphatic amines, acid amides, aminocarboxylic acids, ammonium urea salts, amines, and nitrobenzenesulfonic acid, as well as nitrogen compounds such as urea, ammonium salts, and nitrates. The preferred individual content of each of these is 0.5 to 50 g / L.(8) Solvent

[0044] The solvent for the composition for chemical conversion treatment according to the present embodiment is primarily water. From the perspective of stabilizing the components, water-soluble organic solvents such as alcohols, ethers, and esters may be mixed in. The ratio of organic solvent to the total solvent is not particularly limited, but from the perspective of ensuring appropriate wastewater treatability, a ratio of 10 mass% or less may be preferred.(9) pH

[0045] The pH of the composition for chemical conversion treatment according to the present embodiment is not particularly limited, provided that it is acidic, but a pH range of 1 to 4 is preferred, and a pH of 2 to 3 is particularly preferred from the perspective of stability of the composition for chemical conversion treatment. The pH adjustment may be performed using alkaline substances such as sodium hydroxide, sodium bicarbonate, and ammonia, or acidic substances such as hydrochloric acid, nitric acid, and sulfuric acid.(10) Overcoat

[0046] After the chemical conversion treatment using the composition for chemical conversion treatment according to the present embodiment, washing with water and carrying out an inorganic, organic, or organic-inorganic composite coating before or after drying further improves the corrosion resistance. Inorganic overcoats include silica-based and phosphate-based overcoats, but other overcoats are also possible. Organic overcoats can be used with any paint or resin, and may be water-based or non-water-based. Examples include, but are not limited to, organic coating films such as those of 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 the chemical conversion treatment, or after secondary processing such as secondary processing such as bending or other forming. The number of overcoats is also not limited. The overcoat method is also not particularly limited, and various methods are possible, including paint coating, dip coating, electrostatic coating, electrodeposition coating, and powder coating.(11) Base Material

[0047] Materials for the member (base material) to be chemically treated are not limited, provided that the chemical conversion treatment using the composition for chemical conversion treatment according to the present embodiment proceeds appropriately. An example of the base material is a base material having a surface of a zinc-containing material. Specific examples of such base materials include iron-based members plated with zinc or zinc alloy. Even with such base materials, the composition for chemical conversion treatment according to the present embodiment can be used to perform chemical conversion treatments appropriately over long periods of time, as described previously.[Examples]

[0048] The effects of the present invention will be described below based on examples, but the present invention is not limited to these. Chemical conversion treatments were performed using those in which a phosphorus-containing compound including an organic phosphonic acid compound was contained in a composition for chemical conversion treatment containing an organic sulfur compound and capable of forming a black coating film and the ratio of the vanadium-equivalent molar concentration of a vanadium-containing substance to the hydroxycarboxylic acid-equivalent molar concentration of a hydroxycarboxylic acid-containing substance was 1:0.5 to 1:10. As the cumulative treated area was increased under the fixed-quantity replenishment of the composition for chemical conversion treatment, changes in the appearance and corrosion resistance of the black coating film were confirmed. It is to be note that all of the compositions for chemical conversion treatment used in the examples were substantially free of hexavalent chromium, i.e., so-called hexavalent chromium-free compositions.(1) Preparation of Compositions for Chemical Conversion Treatment

[0049] First, compositions for chemical conversion treatment having the compositions listed in Tables 1 to 3 were prepared. The pH was adjusted to 2.4 using hydrochloric acid and sodium hydroxide. The values of chromium, nickel, and cobalt 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, respectively, in the composition for chemical conversion treatment.

[0050] Table 4 lists compositions for chemical conversion treatment having the compositions of Patent Document 1, which were prepared as comparative examples (Examples 19 to 26). Furthermore, Table 5 lists compositions for chemical conversion treatment having the compositions of Patent Document 2, which were also prepared as comparative examples (Examples 27 and 28). The content of each transition metal (nickel, vanadium, manganese) used in the compositions for chemical conversion treatment according to Examples 20 to 27 was 5 g / L, the median value of the range of 0.1 to 10 g / L, which is considered to be the more preferred addition amount described in Patent Document 1. [Table 1]ComponentExample 1Example 2Example 3Example 4Example 5Example 6Example 7Chromium (g / L)3.73.73.73.73.73.73.7Cobalt (g / L)000000.30.5Nickel (g / L)0.70.70.70.70.70.70.7Diammonium dithioglycolate (g / L)5.35.35.35.35.35.35.3Hydroxyethylidene-1, diphosphonic acid (g / L)2.42.42.42.42.42.42.4Vanadium: Hydroxycarboxylic Acid1:0.51:11:21:51:101:51:5Vanadium (mol / L)0.010.010.010.010.010.010.01Lactic acid (mol / L)0.0050.010.020.050.10.050.05Malic acid (mol / L)0000000Citric acid (mol / L)0000000pH2.42.42.42.42.42.42.4Treatment temperature (°C)35353535353535Treatment time (s)45454545454545 [Table 2] ComponentExample 8Example 9Example 10Example 11Example 12Chromium (g / L)3.73.73.73.73.7Cobalt (g / L)0000.30.5Nickel (g / L)0.70.70.70.70.7Diammonium dithioglycolate (g / L)5.35.35.35.35.3Hydroxyethylidene-1, diphosphonic acid (g / L)2.42.42.42.42.4Vanadium: Hydroxycarboxylic Acid1:11:51:101:51:5Vanadium (mol / L)0.010.010.010.010.01Lactic acid (mol / L)00000Malic acid (mol / L)0.010.050.10.050.05Citric acid (mol / L)00000pH2.42.42.42.42.4Treatment temperature (°C)3535353535Treatment time (s)4545454545 [Table 3] ComponentExample 13Example 14Example 15Example 16Example 17Example 18Chromium (g / L)3.73.73.73.73.73.7Cobalt (g / L)00000.30.5Nickel (g / L)0.70.70.70.70.70.7Diammonium dithioglycolate (g / L)5.35.35.35.35.35.3Hydroxyethylidene-1, diphosphonic acid (g / L)2.42.42.42.42.42.4Vanadium: Hydroxycarboxylic Acid1:11:51:101:51:51:5Vanadium (mol / L)0.010.010.010.010.010.01Lactic acid (mol / L)000000Malic acid (mol / L)000000Citric acid (mol / L)0.010.050.10.050.050.05pH2.42.42.42.42.42.4Treatment temperature (°C)353535353535Treatment time (s)454545454545 [Table 4] Component (g / L)Patent Document 1Example 19Example 20Example 21Example 22Example 23Example 24Example 25Example 26Chromium nitrate1515151515151515Malonic acid10111000Oxalic acid01000111Citric acid55555555Thioglycolic acid55555555Nickel00500500Vanadium00050050Manganese00005005Nitrate ions2020202020202020pH2.02.02.02.02.02.02.02.0Treatment temperature (°C)3030303030303030Treatment time (s)3030303030303030 [Table 5] Component (g / L)Patent Document 2Example 27Example 28Chromium3.73.3Chromium sourceChromium nitrateChromium nitrateCobalt1.40.4Nickel02.4Diammonium dithioglycolate4.02.2Hydroxyethylidene-1, diphosphonic acid0.35.4Oxalic acid03.3pH2.22.2Treatment temperature (°C)3535Treatment time (s)4545 (2) Preparation of Test Members

[0051] Subsequently, the bolts, electrogalvanized according to an ordinary method, were washed with water and then immersed in nitric acid (a 3 mL / L solution of 67.5% nitric acid at a room temperature (25°C) for immersion time of 10 seconds) to activate the surfaces. These test members (base materials) were washed with water for 10 seconds at an ordinary temperature and then immersed for 45 seconds in the compositions for chemical conversion treatment having the compositions listed in Tables 1 to 3, maintained at 35°C and pH 2.4. The test members were removed from the compositions for chemical conversion treatment, washed with water (at an ordinary temperature for 10 seconds), and dried at 80±5°C for 10 minutes.

[0052] In Examples 19 to 26 (Comparative Examples) listed in Table 4, the test members were immersed for 30 seconds in the compositions for chemical conversion treatment maintained at pH 2.0 and 30°C, and in Examples 27 and 28 (Comparative Examples) listed in Table 5, the test members were immersed for 45 seconds in the compositions for chemical conversion treatment maintained at pH 2.2 and 35°C. The test members were removed from the compositions for chemical conversion treatment, washed with water (at an ordinary temperature for 10 seconds), and then dried at 80±5°C for 10 minutes.

[0053] The surface treatments, including the above chemical conversion treatments, were performed on a large number of bolts. The test members for evaluation were those obtained after the first chemical conversion treatment immediately after the bath preparation, and those obtained after the chemical conversion treatments when the cumulative treated area per 1 L reached 250, 500, 750, and 1000 dm 2< . The zinc ion concentration contained in the composition for chemical conversion treatment when the cumulative treated area per 1 L reached 500 dm 2< was approximately 8 g / L, and the zinc ion concentration contained in the composition for chemical conversion treatment when the cumulative treated area per 1 L reached 1000 dm 2< was approximately 15 g / L.(3) Replenishment Method

[0054] As the chemical conversion treatment progressed, the components of the composition for chemical conversion treatment decreased, so a fixed-quantity replenishment was performed every time the treatment area per 1 L increased by 100 dm 2< . The replenishment quantity was determined as follows. First, when the treatment area reached 100 dm 2< per 1 L, the composition for chemical conversion treatment was sampled, from which the chromium concentration was calculated using an ICP optical emission spectrometer ("ARCOS FH522" available from SPECTRO) to determine the amount of chromium reduction in the sample. The amount of chromium reduction in the composition for chemical conversion treatment was calculated by determining the reduction in each component of the composition for chemical conversion treatment at the same rate as this reduction in chromium. As a specific example, if the sample's chromium reduction was 10 mass% when the treatment area per 1 L increased by 100 dm 2< , it was determined that each component of the composition for chemical conversion treatment had decreased by 10 mass%, and replenishment was performed with 1 / 10 the quantity of the composition for chemical conversion treatment at the time of bath preparation.(4) Evaluation Method

[0055] Color tone was determined visually, and corrosion resistance was evaluated using a salt spray test in accordance with JIS Z2371. The presence or absence of white rust was confirmed visually every 24 hours. When the visual white rust area ratio reached 5% of the total area, the cumulative salt spray time for the test member was taken as the time for white rust to appear, and this was used as an index of corrosion resistance.

[0056] The evaluation results are listed in Tables 6 and 7. The columns indicate the appearance and corrosion resistance for the cumulative treated area per 1 L. As a specific example, if it took 96 hours for 5% white rust to appear and the appearance at that time was black, the column would be indicated as "Black / 96 h." [Table 6]ExamplesCumulative treated area per 1 LRemarksInitial liquid (0 dm 2< )250 dm 2< 500 dm 2< 750 dm 2< 1000 dm 2< Example 1Black / 96 hBlack / 96 hBlack / 72 hBlack / 72 hGray / 48 hExample of the inventionExample 2Black / 96 hBlack / 96 hBlack / 96 hBlack / 96 hBlack / 96 hExample of the inventionExample 3Black / 120 hBlack / 120 hBlack / 120 hBlack / 120 hBlack / 120 hExample of the inventionExample 4Black / 120 hBlack / 120 hBlack / 120 hBlack / 120 hBlack / 120 hExample of the inventionExample 5Black / 120 hBlack / 120 hBlack / 120 hBlack / 120 hBlack / 120 hExample of the inventionExample 6Black / 120 hBlack / 120 hBlack / 120 hBlack / 120 hBlack / 120 hExample of the inventionExample 7Black / 144 hBlack / 144 hBlack / 144 hBlack / 120 hBlack / 120 hExample of the inventionExample 8Black / 120 hBlack / 120 hBlack / 120 hBlack / 120 hBlack / 120 hExample of the inventionExample 9Black / 120 hBlack / 120 hBlack / 120 hBlack / 120 hBlack / 120 hExample of the inventionExample 10Black / 120 hBlack / 120 hBlack / 120 hBlack / 120 hBlack / 96 hExample of the inventionExample 11Black / 120 hBlack / 120 hBlack / 120 hBlack / 120 hBlack / 120 hExample of the inventionExample 12Black / 144 hBlack / 144 hBlack / 144 hBlack / 144 hBlack / 120 hExample of the inventionExample 13Black / 120 hBlack / 120 hBlack / 120 hBlack / 120 hBlack / 120 hExample of the inventionExample 14Black / 120 hBlack / 120 hBlack / 120 hBlack / 120 hBlack / 120 hExample of the inventionExample 15Black / 96 hBlack / 96 hBlack / 96 hBlack / 96 hBlack / 96 hExample of the inventionExample 16Black / 120 hBlack / 120 hBlack / 120 hBlack / 120 hBlack / 120 hExample of the inventionExample 17Black / 120 hBlack / 120 hBlack / 120 hBlack / 120 hBlack / 120 hExample of the inventionExample 18Black / 120 hBlack / 120 hBlack / 120 hBlack / 120 hBlack / 120 hExample of the invention [Table 7] Patent Document 1Cumulative treated area per 1 LRemarksInitial liquid (0 dm 2< )250 dm 2< 500 dm 2< 750 dm 2< 1000 dm 2< Example 19Black / 72 hBlack / 72 hBlack / 48 hGray / 24 hGray / 24 hComparative ExampleExample 20Black / 72 hBlack / 72 hBlack / 48 hGray / 24 hGray / 24 hComparative ExampleExample 21Black / 72 hBlack / 48 hBlack / 24 hGray / 24 hGray / 24 hComparative ExampleExample 22Black / 72 hBlack / 72 hBlack / 48 hGray / 24 hGray / 24 hComparative ExampleExample 23Black / 72 hBlack / 72 hBlack / 48 hGray / 24 hGray / 24 hComparative ExampleExample 24Black / 72 hBlack / 48 hBlack / 48 hGray / 24 hGray / 24 hComparative ExampleExample 25Black / 72 hBlack / 72 hBlack / 48 hGray / 24 hGray / 24 hComparative ExampleExample 26Black / 72 hBlack / 48 hBlack / 48 hGray / 24 hGray / 24 hComparative Example Patent Document 2Cumulative treated area per 1 LRemarksInitial liquid (0 dm 2< )250 dm 2< 500 dm 2< 750 dm 2< 1000 dm 2< Example 27Black / 96 hBlack / 72 hBlack / 48 hGray / 48 hGray / 24 hComparative ExampleExample 28Black / 96 hBlack / 72 hBlack / 48 hGray / 24 hGray / 24 hComparative Example

Examples

examples

[Examples]

[0048]The effects of the present invention will be described below based on examples, but the present invention is not limited to these. Chemical conversion treatments were performed using those in which a phosphorus-containing compound including an organic phosphonic acid compound was contained in a composition for chemical conversion treatment containing an organic sulfur compound and capable of forming a black coating film and the ratio of the vanadium-equivalent molar concentration of a vanadium-containing substance to the hydroxycarboxylic acid-equivalent molar concentration of a hydroxycarboxylic acid-containing substance was 1:0.5 to 1:10. As the cumulative treated area was increased under the fixed-quantity replenishment of the composition for chemical conversion treatment, changes in the appearance and corrosion resistance of the black coating film were confirmed. It is to be note that all of the compositions for chemical conversion treatment used in the examples ...

TECHNICAL FIELD

[0001] The present invention relates to a composition for chemical conversion treatment that substantially does not contain hexavalent chromium ions, which are harmful to the natural environment, i.e., is hexavalent chromium-free, is capable of forming a black coating film containing trivalent chromium on the metal surface of a member, and has stable performance and a long bath life even when operated under fixed-quantity replenishment management, and relates also to a method for producing a member provided with a chemical conversion coating film formed using the composition for chemical conversion treatment.BACKGROUND ART

[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] In response to this trend, chromate coating films, which are effective as corrosion-protective chemical conversion coating films for members with metal surfaces such as zinc-plated members, are increasingly being formed using, as a composition for forming a chemical conversion coating film by chemical conversion treatment (this composition will be referred to as a "composition for chemical conversion treatment" in the present specification), a composition for chemical conversion treatment containing trivalent chromium ions rather than using a chromate containing hexavalent chromium ions.

[0004] Some of these compositions for chemical conversion treatment form chemical conversion coating films with a black appearance (these chemical conversion coating films will be referred to as "black coating films" in the present specification). They are widely used on members (press-formed products such as plates, housings, hinges, and panels) and parts (fasteners such as bolts and nuts, attachments such as clamps and clips, etc.) for office equipment, electrical equipment, and automobiles. However, problems have arisen in that the stability of these compositions for chemical conversion treatment deteriorates, as well as in that the appearance of the black coating film deteriorates as the cumulative amount of the treated area of members or the like treated with the composition for chemical conversion treatment (simply referred to as a "cumulative treated area," hereinafter) increases, that is, the black appearance is no longer achieved and the coating film turns gray.

[0005] To address the problem of deterioration in the stability, a method has been proposed in which the stability is improved by adding two types of specific organic acids or their salts, for example, as in Patent Document 1. To address the deterioration in appearance of the black coating film due to an increase in the cumulative treated area, a method has been proposed, as in Patent Document 2, in which an organic sulfur compound and an organic phosphonic acid compound composed of one or more compounds selected from the group consisting of organic phosphonic acids and their ions and salts are added.PRIOR ART DOCUMENTS[Patent documents]

[0006] [Patent Document 1] JP6532003B [Patent Document 2] JP4840790B OBJECT AND SUMMARY OF THE INVENTION

[0007] However, the inventors' investigations have revealed that the method of adding two specific organic acids or their salts, as in Patent Document 1, fails to achieve both the high corrosion resistance and the deterioration in appearance due to an increase in the cumulative treated area. It has also been found that the method of adding an organic sulfur compound and an organic phosphonic acid compound, as in Patent Document 2, preferably increases the amount of the above compounds added as the cumulative treated area increases in order to maintain a good black appearance and high corrosion resistance. In other words, it has been revealed that the method of Patent Document 2 leaves room for improvement from the viewpoint of its suitability for fixed-quantity replenishment management, which assumes continuous treatment.

[0008] In this context, a problem to be solved by the present invention is to provide a composition for chemical conversion treatment that can form a chemical conversion coating film that achieves both the black appearance and the high corrosion resistance even when the cumulative treated area increases with fixed-quantity replenishment, and a method for producing a member provided with such a chemical conversion coating film.

[0009] The inventors have conducted extensive research to solve the above problem. As a result, a knowledge has been obtained that by containing a vanadium-containing substance and a hydroxycarboxylic acid-containing substance in a specific ratio, a composition for chemical conversion treatment can be obtained that is capable of forming a chemical conversion coating film in which both the black appearance and the high corrosion resistance are achieved even when the cumulative treated area is increased through fixed-quantity replenishment management.

[0010] An aspect of the present invention obtained based on the above knowledge provides a composition for chemical conversion treatment 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.

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

[0012] In the above composition for chemical conversion treatment, the content of the trivalent chromium-containing substance may be 1 to 10 g / L in terms of chromium equivalent, 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 above composition for chemical conversion treatment may contain one or more substances selected from a group consisting of nickel-containing substances and cobalt-containing substances.

[0014] The above composition for chemical conversion treatment may contain a zinc-containing substance of a content of 15 g / L or less in terms of zinc equivalent.

[0015] Another aspect of the present invention provides a production method for a member provided with a chemical conversion coating film, the method comprising contacting the above composition for chemical conversion treatment with a base material having a surface of a material containing zinc. The composition for chemical conversion treatment may be preferably managed by fixed-quantity replenishment.

[0016] Using the composition for chemical conversion treatment according to the above invention, even when the cumulative treated area increases through fixed-quantity replenishment management, it is possible to consistently form a black coating film that is black in appearance and has excellent corrosion resistance. Therefore, compared to conventional techniques, the composition for chemical conversion treatment according to the present invention stabilizes the quality with simpler management (fixed-quantity replenishment), and it can thus contribute to stabilizing the quality in mass production.BEST MODE FOR CARRYING OUT THE INVENTION

[0017] The composition for chemical conversion treatment according to an 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. 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. The composition for chemical conversion treatment substantially does not contain hexavalent chromium ions, that is, it is a hexavalent chromium-free aqueous composition.

[0018] By carrying out a process of contacting the composition for chemical conversion treatment according to the present embodiment with a member having a surface made of a metal material such as zinc plating, a chemical conversion coating film having a black appearance and high corrosion resistance is formed. Furthermore, since its performance is unlikely to change even when the cumulative treated area increases with fixed-quantity replenishment management, the quality can be stabilized with simple management (fixed-quantity replenishment).

[0019] Each component will be described in detail below.(1) Trivalent Chromium-Containing Substance

[0020] The composition for chemical conversion treatment according to the present embodiment contains a trivalent chromium-containing substance. The trivalent chromium-containing substance is composed of one or more substances selected from the group consisting of trivalent chromium and a water-soluble substance containing trivalent chromium (e.g., trivalent chromium complexes). It is preferred to use a compound capable of generating a trivalent chromium-containing substance in water (referred to as a "trivalent chromium compound," hereinafter) as the raw material for the trivalent chromium-containing substance.

[0021] 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 ones with a reducing agent. The trivalent chromium compound may be composed of only one compound or two or more types. Preferred examples of trivalent chromium compounds are chromium nitrate and chromium chloride. The composition for chemical conversion treatment according to the present invention is substantially free of hexavalent chromium, or so-called hexavalent chromium-free, because hexavalent chromium compounds are not actively added as raw materials to the composition for chemical conversion treatment according to the present invention.

[0022] The content of the trivalent chromium-containing substance is preferably 1 g / L or more in terms of chromium equivalent from the perspective of stably forming a chemical conversion coating film. The upper limit of the trivalent chromium-containing substance content is not particularly limited, but a preferred upper limit is approximately 10 g / L from the perspective of appropriately ensuring the effects of containing the trivalent chromium-containing substance without increasing the burden on wastewater treatment. Furthermore, from the perspective of ease of forming a chemical conversion coating film, the content of the trivalent chromium-containing substance is preferably 2 to 5 g / L.(2) Organic Sulfur Compound

[0023] The composition for chemical conversion treatment according to the present embodiment contains an organic sulfur compound, which is an organic compound containing sulfur as its 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), -CSSH (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-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.

[0024] Among these organic sulfur compounds, it is preferred to include one or more selected from the group consisting of thioglycolic acid, dithiodiglycolic acid, and their ions and salts in order to consistently obtain a black coating film.

[0025] Organic sulfur compounds are considered to be one of the components that directly affect the blackening of the chemical conversion coating film, and the content is preferably 0.1 to 10 g / L. At a content of less than 0.1 g / L, the blackening effect is weak, and even at additions exceeding 10 g / L, the blackening effect saturates. From the perspective of stably forming a black coating film while adequately ensuring the effects of containing 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.(3) Organic Phosphonic Acid Compound

[0026] The "organic phosphonic acid compound" according to the present embodiment means a substance composed of one or more selected from the group consisting of organic phosphonic acids and their ions and salts. Here, the "organic phosphonic acid" refers to a compound having the rational formula R-P(=O)(OH) 2 (where 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 these salts, the sodium ion is often dissociated in the composition for chemical conversion treatment.

[0027] 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 film tends to be insufficient, while even if the content exceeds 20 g / L, the formation of the chemical conversion coating film saturates. From the perspective of stably forming a chemical conversion coating film while appropriately ensuring the effects 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.(4) Vanadium-Containing Substance

[0028] The composition for chemical conversion treatment according to the present embodiment contains a vanadium-containing substance. The vanadium-containing substance is composed of one or more substances selected from the group consisting of water-soluble substances containing vanadium, including vanadium ions and their complexes, as well as vanadium oxyacid ions such as vanadate ions. It is preferred to use a compound capable of generating a vanadium-containing substance in water (referred to as a "vanadium compound," hereinafter) as the raw material for the vanadium-containing substance.

[0029] 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 also be two or more types.

[0030] The molar concentration of the vanadium-containing substance is preferably 0.001 mol / L or more and 1 mol / L or less in terms of vanadium equivalent. If the above molar concentration is less than 0.001 mol / L, it may be difficult to obtain a chemical conversion coating film with a black appearance, while if it exceeds 1 mol / L, the stability of the composition for chemical conversion treatment may tend to decrease. From the perspective of obtaining a good chemical conversion coating while maintaining the stability of the composition for chemical conversion treatment, it may be more preferred for the vanadium-equivalent molar concentration of the vanadium-containing substance to be 0.002 to 0.5 mol / L and particularly preferably 0.005 to 0.1 mol / L.(5) Hydroxycarboxylic Acid-Containing Substance

[0031] The composition for chemical conversion treatment according to the present embodiment contains a hydroxycarboxylic acid-containing substance. In the present specification, the hydroxycarboxylic acid-containing substance is composed of one or more substances selected from the group consisting of water-soluble substances containing hydroxycarboxylic acids, which are carboxylic acids having a hydroxyl group, and substances based thereon. It is preferred to use a water-soluble compound capable of being dissolved in water to generate the hydroxycarboxylic acid-containing substance as the raw material for the hydroxycarboxylic acid-containing substance (the water-soluble compound is referred to as a "water-soluble hydroxycarboxylic acid compound," hereinafter). Water-soluble hydroxycarboxylic acid compounds also include esters that generate hydroxycarboxylic acids upon hydrolysis.

[0032] 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 and potassium salts.

[0033] The molar concentration of the hydroxycarboxylic acid-containing substance is preferably 0.001 mol / L or more and 5 mol / L or less in terms of hydroxycarboxylic acid equivalent. If the above molar concentration is less than 0.001 mol / L, the stability of the composition for chemical conversion treatment may tend to deteriorate, while if the above molar concentration exceeds 5 mol / L, the load during wastewater treatment of the composition for chemical conversion treatment may increase. From the perspective of ensuring the stability and wastewater treatability of the composition for chemical conversion treatment, the hydroxycarboxylic acid-equivalent molar concentration of the hydroxycarboxylic acid-containing substance may be preferably 0.002 to 5 mol / L and particularly preferably 0.005 to 1 mol / L.

[0034] In the composition for chemical conversion treatment according to the present 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 range, a chemical conversion coating film having a black appearance and high corrosion resistance can be consistently obtained even when the cumulative treated area is large.(6) Nickel-Containing Substance and Cobalt-Containing Substance

[0035] The composition for chemical conversion treatment according to the present 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 composed of one or more substances selected from the group consisting of water-soluble substances containing nickel, including nickel ions and their complexes. The cobalt-containing substance is composed of one or more substances selected from the group consisting of water-soluble substances containing cobalt, including cobalt ions and their complexes. The nickel-containing substance contributes to blackening, while the cobalt-containing substance contributes to improvement of corrosion resistance. It is desirable to use compounds (nickel compounds, cobalt compounds) capable of generating the nickel-containing substance and cobalt-containing substance in water as raw materials for the nickel-containing substance and cobalt-containing substance.

[0036] Examples of nickel compounds include nickel chloride, nickel sulfate, nickel nitrate, nickel phosphate, and nickel acetate. The nickel compound may be composed only of one type of compound or may also be composed of two or more types. Examples of cobalt compounds include cobalt chloride, cobalt sulfate, cobalt nitrate, cobalt phosphate, and cobalt acetate. The cobalt compound may be composed only of one type of compound or may also be composed of two or more types.

[0037] When a nickel-containing substance is contained, its content is preferably 0.05 to 5 g / L in terms of nickel equivalent. If its content is less than 0.05 g / L, the effect of improving blackening may be difficult to achieve, while if it exceeds 5 g / L, corrosion resistance may decrease. From the perspective of consistently achieving the blackening effect while minimizing the impact on corrosion resistance, it may be preferred for the nickel-containing substance content to be 0.1 to 3 g / L in terms of nickel equivalent. When a cobalt-containing substance is contained, its content is preferably 0.05 to 5 g / L in terms of cobalt equivalent. If its content is less than 0.05 g / L, the effect of improving corrosion resistance may be difficult to achieve, while if it exceeds 5 g / L, corrosion resistance may rather decrease. From the perspective of consistently achieving the effect of improving corrosion resistance, it may be preferred for the cobalt-containing substance content to be 0.1 to 3 g / L in terms of cobalt equivalent.(7) Other Components

[0038] In addition to the above substances, the composition for chemical conversion treatment according to the present embodiment may contain one or more substances 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 substances selected from the group consisting of polymers such as wax, corrosion inhibitors, surfactants, plastic dispersants, color formers such as dyes and pigments, desiccants, and dispersants. A reducing substance may also be added simultaneously.

[0039] 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 ions may exist in the form of oxyacid ions. When the member (base material) to be subjected to chemical conversion treatment has a surface of a material containing zinc, zinc-containing substances (specifically, zinc ions and their complexes) accumulate in the composition for chemical conversion treatment as the cumulative treated area increases. In general, as the zinc-equivalent concentration of the zinc-containing substance in the composition for chemical conversion treatment increases, it becomes difficult to maintain the black appearance of the chemical conversion coating film. Fortunately, however, the composition for chemical conversion treatment according to the present embodiment can achieve a black appearance even with a zinc-equivalent content of 15 g / L of this zinc-containing substance, so the zinc-containing substance may be contained within this range (15 g / L or less).

[0040] 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. Phosphorus-containing inorganic acids such as phosphoric acid (orthophosphoric acid), polyphosphoric acid, metaphosphoric acid, pyrophosphoric acid, ultraphosphoric acid, hypophosphorous acid, and superphosphoric acid may also be contained. The inorganic acids may be contained in the composition for chemical conversion treatment as ions.

[0041] The molar concentration of these inorganic acids and / or their ions in the composition for chemical conversion treatment is not particularly limited. The total molar concentration of the inorganic acids and their ions, expressed as a ratio to the total molar concentration of trivalent chromium ions and the above metal ions (such as vanadium-containing ions, nickel ions, and cobalt ions), may preferably be 0.1 to 10 and more preferably 0.5 to 3.

[0042] Examples of inorganic colloids include silica sol, alumina sol, titanium sol, and zirconia sol. Examples of silane coupling agents include organic silane coupling agents such as vinyltriethoxysilane.

[0043] Examples of nitrogen compounds include organic nitrogen compounds such as heterocyclic compounds, ureas, aliphatic amines, acid amides, aminocarboxylic acids, ammonium urea salts, amines, and nitrobenzenesulfonic acid, as well as nitrogen compounds such as urea, ammonium salts, and nitrates. The preferred individual content of each of these is 0.5 to 50 g / L.(8) Solvent

[0044] The solvent for the composition for chemical conversion treatment according to the present embodiment is primarily water. From the perspective of stabilizing the components, water-soluble organic solvents such as alcohols, ethers, and esters may be mixed in. The ratio of organic solvent to the total solvent is not particularly limited, but from the perspective of ensuring appropriate wastewater treatability, a ratio of 10 mass% or less may be preferred.(9) pH

[0045] The pH of the composition for chemical conversion treatment according to the present embodiment is not particularly limited, provided that it is acidic, but a pH range of 1 to 4 is preferred, and a pH of 2 to 3 is particularly preferred from the perspective of stability of the composition for chemical conversion treatment. The pH adjustment may be performed using alkaline substances such as sodium hydroxide, sodium bicarbonate, and ammonia, or acidic substances such as hydrochloric acid, nitric acid, and sulfuric acid.(10) Overcoat

[0046] After the chemical conversion treatment using the composition for chemical conversion treatment according to the present embodiment, washing with water and carrying out an inorganic, organic, or organic-inorganic composite coating before or after drying further improves the corrosion resistance. Inorganic overcoats include silica-based and phosphate-based overcoats, but other overcoats are also possible. Organic overcoats can be used with any paint or resin, and may be water-based or non-water-based. Examples include, but are not limited to, organic coating films such as those of 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 the chemical conversion treatment, or after secondary processing such as secondary processing such as bending or other forming. The number of overcoats is also not limited. The overcoat method is also not particularly limited, and various methods are possible, including paint coating, dip coating, electrostatic coating, electrodeposition coating, and powder coating.(11) Base Material

[0047] Materials for the member (base material) to be chemically treated are not limited, provided that the chemical conversion treatment using the composition for chemical conversion treatment according to the present embodiment proceeds appropriately. An example of the base material is a base material having a surface of a zinc-containing material. Specific examples of such base materials include iron-based members plated with zinc or zinc alloy. Even with such base materials, the composition for chemical conversion treatment according to the present embodiment can be used to perform chemical conversion treatments appropriately over long periods of time, as described previously.[Examples]

[0048] The effects of the present invention will be described below based on examples, but the present invention is not limited to these. Chemical conversion treatments were performed using those in which a phosphorus-containing compound including an organic phosphonic acid compound was contained in a composition for chemical conversion treatment containing an organic sulfur compound and capable of forming a black coating film and the ratio of the vanadium-equivalent molar concentration of a vanadium-containing substance to the hydroxycarboxylic acid-equivalent molar concentration of a hydroxycarboxylic acid-containing substance was 1:0.5 to 1:10. As the cumulative treated area was increased under the fixed-quantity replenishment of the composition for chemical conversion treatment, changes in the appearance and corrosion resistance of the black coating film were confirmed. It is to be note that all of the compositions for chemical conversion treatment used in the examples were substantially free of hexavalent chromium, i.e., so-called hexavalent chromium-free compositions.(1) Preparation of Compositions for Chemical Conversion Treatment

[0049] First, compositions for chemical conversion treatment having the compositions listed in Tables 1 to 3 were prepared. The pH was adjusted to 2.4 using hydrochloric acid and sodium hydroxide. The values of chromium, nickel, and cobalt 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, respectively, in the composition for chemical conversion treatment.

[0050] Table 4 lists compositions for chemical conversion treatment having the compositions of Patent Document 1, which were prepared as comparative examples (Examples 19 to 26). Furthermore, Table 5 lists compositions for chemical conversion treatment having the compositions of Patent Document 2, which were also prepared as comparative examples (Examples 27 and 28). The content of each transition metal (nickel, vanadium, manganese) used in the compositions for chemical conversion treatment according to Examples 20 to 27 was 5 g / L, the median value of the range of 0.1 to 10 g / L, which is considered to be the more preferred addition amount described in Patent Document 1. [Table 1]ComponentExample 1Example 2Example 3Example 4Example 5Example 6Example 7Chromium (g / L)3.73.73.73.73.73.73.7Cobalt (g / L)000000.30.5Nickel (g / L)0.70.70.70.70.70.70.7Diammonium dithioglycolate (g / L)5.35.35.35.35.35.35.3Hydroxyethylidene-1, diphosphonic acid (g / L)2.42.42.42.42.42.42.4Vanadium: Hydroxycarboxylic Acid1:0.51:11:21:51:101:51:5Vanadium (mol / L)0.010.010.010.010.010.010.01Lactic acid (mol / L)0.0050.010.020.050.10.050.05Malic acid (mol / L)0000000Citric acid (mol / L)0000000pH2.42.42.42.42.42.42.4Treatment temperature (°C)35353535353535Treatment time (s)45454545454545 [Table 2] ComponentExample 8Example 9Example 10Example 11Example 12Chromium (g / L)3.73.73.73.73.7Cobalt (g / L)0000.30.5Nickel (g / L)0.70.70.70.70.7Diammonium dithioglycolate (g / L)5.35.35.35.35.3Hydroxyethylidene-1, diphosphonic acid (g / L)2.42.42.42.42.4Vanadium: Hydroxycarboxylic Acid1:11:51:101:51:5Vanadium (mol / L)0.010.010.010.010.01Lactic acid (mol / L)00000Malic acid (mol / L)0.010.050.10.050.05Citric acid (mol / L)00000pH2.42.42.42.42.4Treatment temperature (°C)3535353535Treatment time (s)4545454545 [Table 3] ComponentExample 13Example 14Example 15Example 16Example 17Example 18Chromium (g / L)3.73.73.73.73.73.7Cobalt (g / L)00000.30.5Nickel (g / L)0.70.70.70.70.70.7Diammonium dithioglycolate (g / L)5.35.35.35.35.35.3Hydroxyethylidene-1, diphosphonic acid (g / L)2.42.42.42.42.42.4Vanadium: Hydroxycarboxylic Acid1:11:51:101:51:51:5Vanadium (mol / L)0.010.010.010.010.010.01Lactic acid (mol / L)000000Malic acid (mol / L)000000Citric acid (mol / L)0.010.050.10.050.050.05pH2.42.42.42.42.42.4Treatment temperature (°C)353535353535Treatment time (s)454545454545 [Table 4] Component (g / L)Patent Document 1Example 19Example 20Example 21Example 22Example 23Example 24Example 25Example 26Chromium nitrate1515151515151515Malonic acid10111000Oxalic acid01000111Citric acid55555555Thioglycolic acid55555555Nickel00500500Vanadium00050050Manganese00005005Nitrate ions2020202020202020pH2.02.02.02.02.02.02.02.0Treatment temperature (°C)3030303030303030Treatment time (s)3030303030303030 [Table 5] Component (g / L)Patent Document 2Example 27Example 28Chromium3.73.3Chromium sourceChromium nitrateChromium nitrateCobalt1.40.4Nickel02.4Diammonium dithioglycolate4.02.2Hydroxyethylidene-1, diphosphonic acid0.35.4Oxalic acid03.3pH2.22.2Treatment temperature (°C)3535Treatment time (s)4545 (2) Preparation of Test Members

[0051] Subsequently, the bolts, electrogalvanized according to an ordinary method, were washed with water and then immersed in nitric acid (a 3 mL / L solution of 67.5% nitric acid at a room temperature (25°C) for immersion time of 10 seconds) to activate the surfaces. These test members (base materials) were washed with water for 10 seconds at an ordinary temperature and then immersed for 45 seconds in the compositions for chemical conversion treatment having the compositions listed in Tables 1 to 3, maintained at 35°C and pH 2.4. The test members were removed from the compositions for chemical conversion treatment, washed with water (at an ordinary temperature for 10 seconds), and dried at 80±5°C for 10 minutes.

[0052] In Examples 19 to 26 (Comparative Examples) listed in Table 4, the test members were immersed for 30 seconds in the compositions for chemical conversion treatment maintained at pH 2.0 and 30°C, and in Examples 27 and 28 (Comparative Examples) listed in Table 5, the test members were immersed for 45 seconds in the compositions for chemical conversion treatment maintained at pH 2.2 and 35°C. The test members were removed from the compositions for chemical conversion treatment, washed with water (at an ordinary temperature for 10 seconds), and then dried at 80±5°C for 10 minutes.

[0053] The surface treatments, including the above chemical conversion treatments, were performed on a large number of bolts. The test members for evaluation were those obtained after the first chemical conversion treatment immediately after the bath preparation, and those obtained after the chemical conversion treatments when the cumulative treated area per 1 L reached 250, 500, 750, and 1000 dm 2< . The zinc ion concentration contained in the composition for chemical conversion treatment when the cumulative treated area per 1 L reached 500 dm 2< was approximately 8 g / L, and the zinc ion concentration contained in the composition for chemical conversion treatment when the cumulative treated area per 1 L reached 1000 dm 2< was approximately 15 g / L.(3) Replenishment Method

[0054] As the chemical conversion treatment progressed, the components of the composition for chemical conversion treatment decreased, so a fixed-quantity replenishment was performed every time the treatment area per 1 L increased by 100 dm 2< . The replenishment quantity was determined as follows. First, when the treatment area reached 100 dm 2< per 1 L, the composition for chemical conversion treatment was sampled, from which the chromium concentration was calculated using an ICP optical emission spectrometer ("ARCOS FH522" available from SPECTRO) to determine the amount of chromium reduction in the sample. The amount of chromium reduction in the composition for chemical conversion treatment was calculated by determining the reduction in each component of the composition for chemical conversion treatment at the same rate as this reduction in chromium. As a specific example, if the sample's chromium reduction was 10 mass% when the treatment area per 1 L increased by 100 dm 2< , it was determined that each component of the composition for chemical conversion treatment had decreased by 10 mass%, and replenishment was performed with 1 / 10 the quantity of the composition for chemical conversion treatment at the time of bath preparation.(4) Evaluation Method

[0055] Color tone was determined visually, and corrosion resistance was evaluated using a salt spray test in accordance with JIS Z2371. The presence or absence of white rust was confirmed visually every 24 hours. When the visual white rust area ratio reached 5% of the total area, the cumulative salt spray time for the test member was taken as the time for white rust to appear, and this was used as an index of corrosion resistance.

[0056] The evaluation results are listed in Tables 6 and 7. The columns indicate the appearance and corrosion resistance for the cumulative treated area per 1 L. As a specific example, if it took 96 hours for 5% white rust to appear and the appearance at that time was black, the column would be indicated as "Black / 96 h." [Table 6]ExamplesCumulative treated area per 1 LRemarksInitial liquid (0 dm 2< )250 dm 2< 500 dm 2< 750 dm 2< 1000 dm 2< Example 1Black / 96 hBlack / 96 hBlack / 72 hBlack / 72 hGray / 48 hExample of the inventionExample 2Black / 96 hBlack / 96 hBlack / 96 hBlack / 96 hBlack / 96 hExample of the inventionExample 3Black / 120 hBlack / 120 hBlack / 120 hBlack / 120 hBlack / 120 hExample of the inventionExample 4Black / 120 hBlack / 120 hBlack / 120 hBlack / 120 hBlack / 120 hExample of the inventionExample 5Black / 120 hBlack / 120 hBlack / 120 hBlack / 120 hBlack / 120 hExample of the inventionExample 6Black / 120 hBlack / 120 hBlack / 120 hBlack / 120 hBlack / 120 hExample of the inventionExample 7Black / 144 hBlack / 144 hBlack / 144 hBlack / 120 hBlack / 120 hExample of the inventionExample 8Black / 120 hBlack / 120 hBlack / 120 hBlack / 120 hBlack / 120 hExample of the inventionExample 9Black / 120 hBlack / 120 hBlack / 120 hBlack / 120 hBlack / 120 hExample of the inventionExample 10Black / 120 hBlack / 120 hBlack / 120 hBlack / 120 hBlack / 96 hExample of the inventionExample 11Black / 120 hBlack / 120 hBlack / 120 hBlack / 120 hBlack / 120 hExample of the inventionExample 12Black / 144 hBlack / 144 hBlack / 144 hBlack / 144 hBlack / 120 hExample of the inventionExample 13Black / 120 hBlack / 120 hBlack / 120 hBlack / 120 hBlack / 120 hExample of the inventionExample 14Black / 120 hBlack / 120 hBlack / 120 hBlack / 120 hBlack / 120 hExample of the inventionExample 15Black / 96 hBlack / 96 hBlack / 96 hBlack / 96 hBlack / 96 hExample of the inventionExample 16Black / 120 hBlack / 120 hBlack / 120 hBlack / 120 hBlack / 120 hExample of the inventionExample 17Black / 120 hBlack / 120 hBlack / 120 hBlack / 120 hBlack / 120 hExample of the inventionExample 18Black / 120 hBlack / 120 hBlack / 120 hBlack / 120 hBlack / 120 hExample of the invention [Table 7] Patent Document 1Cumulative treated area per 1 LRemarksInitial liquid (0 dm 2< )250 dm 2< 500 dm 2< 750 dm 2< 1000 dm 2< Example 19Black / 72 hBlack / 72 hBlack / 48 hGray / 24 hGray / 24 hComparative ExampleExample 20Black / 72 hBlack / 72 hBlack / 48 hGray / 24 hGray / 24 hComparative ExampleExample 21Black / 72 hBlack / 48 hBlack / 24 hGray / 24 hGray / 24 hComparative ExampleExample 22Black / 72 hBlack / 72 hBlack / 48 hGray / 24 hGray / 24 hComparative ExampleExample 23Black / 72 hBlack / 72 hBlack / 48 hGray / 24 hGray / 24 hComparative ExampleExample 24Black / 72 hBlack / 48 hBlack / 48 hGray / 24 hGray / 24 hComparative ExampleExample 25Black / 72 hBlack / 72 hBlack / 48 hGray / 24 hGray / 24 hComparative ExampleExample 26Black / 72 hBlack / 48 hBlack / 48 hGray / 24 hGray / 24 hComparative Example Patent Document 2Cumulative treated area per 1 LRemarksInitial liquid (0 dm 2< )250 dm 2< 500 dm 2< 750 dm 2< 1000 dm 2< Example 27Black / 96 hBlack / 72 hBlack / 48 hGray / 48 hGray / 24 hComparative ExampleExample 28Black / 96 hBlack / 72 hBlack / 48 hGray / 24 hGray / 24 hComparative Example

Examples

examples

[Examples]

[0048]The effects of the present invention will be described below based on examples, but the present invention is not limited to these. Chemical conversion treatments were performed using those in which a phosphorus-containing compound including an organic phosphonic acid compound was contained in a composition for chemical conversion treatment containing an organic sulfur compound and capable of forming a black coating film and the ratio of the vanadium-equivalent molar concentration of a vanadium-containing substance to the hydroxycarboxylic acid-equivalent molar concentration of a hydroxycarboxylic acid-containing substance was 1:0.5 to 1:10. As the cumulative treated area was increased under the fixed-quantity replenishment of the composition for chemical conversion treatment, changes in the appearance and corrosion resistance of the black coating film were confirmed. It is to be note that all of the compositions for chemical conversion treatment used in the examples ...

Claims

1. A composition for chemical conversion treatment 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 composition for chemical conversion treatment according to claim 1, wherein a ratio of a vanadium-equivalent molar concentration of the vanadium-containing substance to a hydroxycarboxylic acid-equivalent molar concentration of the hydroxycarboxylic acid-containing substance is 1:1 to 1:10.

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

4. The composition for chemical conversion treatment according to claim 1 or 2, comprising one or more substances selected from a group consisting of nickel-containing substances and cobalt-containing substances.

5. The composition for chemical conversion treatment according to claim 1 or 2, comprising a zinc-containing substance of a content of 15 g / L or less in terms of zinc equivalent.

6. A production method for a member provided with a chemical conversion coating film, the method comprising contacting the composition for chemical conversion treatment according to claim 1 or 2 with a base material having a surface of a material containing zinc.

7. The production method according to claim 6, wherein the composition for chemical conversion treatment is managed by fixed-quantity replenishment.

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