JP7340900B1 - Trivalent chromium black chemical conversion treatment composition and method for producing a member provided with a chemical conversion film - Google Patents

Abstract

The present invention provides a composition for chemical conversion treatment that can form a chemical conversion film that has both a black appearance and high corrosion resistance even when the cumulative treated area increases due to quantitative replenishment management. A composition for chemical conversion treatment 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, the vanadium-containing substance The ratio of the vanadium equivalent molar concentration of the hydroxycarboxylic acid-containing substance to the hydroxycarboxylic acid equivalent molar concentration of the hydroxycarboxylic acid-containing substance may be 1:1 to 1:10. [Selection diagram] None

Description

The present invention substantially does not contain hexavalent chromium ions that are harmful to the natural environment, that is, it is free of hexavalent chromium, and it is possible to form a black film containing trivalent chromium on the metal surface of the member. The present invention relates to a chemical conversion treatment composition that has stable performance and a long bath life even when operated with fixed-dose replenishment, and a method for producing a member provided with a chemical conversion coating formed from the chemical conversion treatment composition.

In recent years, environmentally friendly directives such as RoHS (Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment) and ELV (End of Life Vehicles) have restricted the use of hazardous substances (lead, mercury, cadmium, hexavalent chromium, ions, etc.) is required to be regulated.

In response to this trend, chromate coatings, which are effective as anticorrosive conversion coatings for members with metal surfaces such as galvanized members, are being developed as a composition for forming a chemical conversion coating through chemical conversion treatment (hereinafter referred to as "this composition"). Instead of using chromate salts containing hexavalent chromium ions, chemical conversion treatment compositions containing trivalent chromium ions are now being used as chemical conversion treatment compositions.

Some of these chemical conversion treatment compositions form a chemical conversion film with a black appearance (in this specification, this chemical conversion film is referred to as a "black film"), and are used for office equipment, electrical equipment, automobiles, etc. (press-formed products such as plates, housings, hinges, panels, etc.) and parts (fastening parts such as bolts and nuts, fasteners such as clamps and clips, etc.), but chemical conversion treatment compositions The problem is that the stability of the chemical conversion treatment composition decreases, and the cumulative amount of treated area (hereinafter abbreviated as "cumulative treated area") of parts, etc. treated with the chemical conversion treatment composition increases. The problem is that the appearance of the material deteriorates, that is, the appearance becomes gray instead of black.

To address the problem of decreased stability, for example, as in Patent Document 1, a method has been proposed in which stability is achieved by adding two types of specific organic acids or salts thereof. For deterioration of the appearance of the black film due to an increase in the cumulative treated area, as in Patent Document 2, one or more selected from the group consisting of organic sulfur compounds, organic phosphonic acids, and their ions and salts can be used. A method of adding an organic phosphonic acid compound has been proposed.

Patent No. 6532003 Patent No. 4840790

However, the present inventors have investigated and found that the method of adding a specific organic acid or two types of salts thereof as in Patent Document 1 is unable to achieve both deterioration in appearance due to an increase in cumulative treated area and high corrosion resistance. In the method of adding organic sulfur compounds and organic phosphonic acid compounds as in Patent Document 2, in order to maintain good black appearance and high corrosion resistance, the amount of the above compounds added must be adjusted as the cumulative treated area increases. It has become clear that it is preferable to increase the In other words, it has become clear that the method of Patent Document 2 has room for improvement from the viewpoint of suitability for quantitative supply management assuming continuous processing.

Therefore, the present invention provides a composition for chemical conversion treatment that can form a chemical conversion film that has both a black appearance and high corrosion resistance even when the cumulative treated area increases due to quantitative supply management, and a method for producing a member equipped with the chemical conversion film. The task is to do so.

In order to solve the above problems, the present inventors conducted extensive studies. As a result, by containing a vanadium-containing substance and a hydroxycarboxylic acid-containing substance in a specific ratio, it is possible to form a chemical conversion film that has both a black appearance and high corrosion resistance even when the cumulative treatment area increases through quantitative supply management. It was found that a composition for chemical conversion treatment can be obtained.

One aspect of the present invention obtained based on the above findings includes a trivalent chromium-containing substance, an organic sulfur compound, an organic phosphonic acid compound, a vanadium-containing substance, and a hydroxycarboxylic acid-containing substance. A composition for chemical conversion treatment is provided.

In the above 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 from 1:1 to 1:10.

In the above composition for chemical conversion treatment, the content of the trivalent chromium-containing substance is 1 to 10 g/L in terms of 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 10 g/L. The content may be 0.1 to 20 g/L.

The above composition for chemical conversion treatment may contain one or more types selected from the group consisting of nickel-containing substances and cobalt-containing substances.

The above composition for chemical conversion treatment may contain a zinc-containing substance in an amount of 15 g/L or less in terms of zinc.

Another aspect of the present invention is a method for producing a member provided with a chemical conversion film, the method comprising bringing the above chemical conversion treatment composition into contact with a base material having a surface of a material containing zinc. provide. It may be preferable that the chemical conversion treatment composition be managed by fixed-quantity replenishment.

By using the composition for chemical conversion treatment according to the above invention, it is possible to stably form a black film that has a black appearance and has excellent corrosion resistance even when the cumulative treatment area increases due to quantitative supply management. . For this reason, the composition for chemical conversion treatment according to the present invention can stabilize quality with simple management (quantitative replenishment) compared to conventional techniques, and therefore can greatly contribute to stabilizing quality in mass production.

A chemical conversion treatment composition 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 containing substance to the hydroxycarboxylic acid equivalent molar concentration of the hydroxycarboxylic acid-containing substance is 1:1 to 1:10, and it does not substantially contain hexavalent chromium ions. It is a chromium-free aqueous composition.

A chemical conversion film having a black appearance and high corrosion resistance is formed by contacting a member having a surface made of a metallic material such as zinc plating with the chemical conversion treatment composition according to the present embodiment. Moreover, even if the cumulative processing area increases with quantitative supply management, the performance does not change easily, so quality can be stabilized with simple management (quantitative supply).

Each component will be explained in detail below.
(1) Substance containing trivalent chromium The composition for chemical conversion treatment according to this embodiment includes a substance containing trivalent chromium. The trivalent chromium-containing substance is composed of one or more types selected from the group consisting of trivalent chromium and water-soluble substances containing this (trivalent chromium complexes are exemplified). It is preferable to use a compound capable of producing a trivalent chromium-containing substance in water (hereinafter referred to as a "trivalent chromium compound") as a raw material for the trivalent chromium-containing substance.

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 hexavalent chromium compounds such as chromic acid and dichromate using a reducing agent. Examples include compounds reduced to trivalent. The trivalent chromium compound may be composed of only one type of compound, or may be composed of multiple types. Examples of preferred trivalent chromium compounds are chromium nitrate and chromium chloride. In addition, since a hexavalent chromium compound is not actively added as a raw material to the chemical conversion treatment composition according to the present invention, the chemical conversion treatment composition according to the present invention does not substantially contain hexavalent chromium. , so-called hexavalent chromium-free.

The content of the trivalent chromium-containing substance is preferably 1 g/L or more in terms of chromium from the viewpoint of stably forming a chemical conversion film. The upper limit of the trivalent chromium-containing substance is not particularly limited, but it is preferable to set the upper limit to about 10 g/L from the viewpoint of appropriately ensuring the effect of containing the trivalent chromium-containing substance and not increasing the burden of waste liquid treatment. Furthermore, from the viewpoint of ease of forming a chemical conversion film, the content of the trivalent chromium-containing substance is preferably 2 to 5 g/L.

(2) Organic sulfur compound The composition for chemical conversion treatment according to the present embodiment contains an organic sulfur compound that is an organic compound containing sulfur as a constituent element. The sulfur-containing functional groups contained in organic sulfur compounds 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, Schaffer's acid, sulfadiazine, rhodanammonium, rhodan potash, rhodan soda, rhodanine, ammonium sulfide, sodium sulfide, ammonium sulfate, thioglycerin, thioacetic acid, potassium thioacetate, thiodiacetic acid, 3,3-thio Dipropionic acid and thiosemicarbazide are mentioned.

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

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

(3) Organic phosphonic acid compound The "organic phosphonic acid compound" according to the present embodiment means a substance consisting of one or more types selected from the group consisting of organic phosphonic acids, ions and salts thereof. Here, the term "organic phosphonic acid" refers to an acid having the formula RP(=O)(OH) ₂ (R is an organic group), in which an organic group is bonded to a phosphonic group. 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). acid) is exemplified. 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, An example is diethylenetriaminepenta(methylenephosphonic acid) heptasodium salt. These salts often contain dissociated sodium ions in the composition for chemical conversion treatment.

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 a chemical conversion film tends to be insufficient, and even if it exceeds 20 g/L, the formation of a chemical conversion film is saturated. From the viewpoint of stably forming a chemical conversion film while appropriately ensuring the effect of containing the organic phosphonic acid compound, the content of the organic phosphonic acid compound is more preferably 0.2 to 15 g/L, and 0.2 to 15 g/L. .3 to 10 g/L is particularly preferred.

(4) Vanadium-containing substance The chemical conversion treatment composition according to this embodiment contains a vanadium-containing substance. The vanadium-containing substance is composed of one or more selected from the group consisting of vanadium-containing water-soluble substances, and includes vanadium ions, complexes thereof, and vanadium oxygen acid ions such as vanadate ions. It is preferable to use a compound capable of producing a vanadium-containing substance in water (hereinafter referred to as a "vanadium compound") as a raw material for the vanadium-containing substance.

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.

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. If the above molar concentration is less than 0.001 mol/L, it may be difficult to obtain a chemical conversion film with 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 film while ensuring the stability of the chemical conversion treatment composition, it may be more preferable that the vanadium equivalent molar concentration of the vanadium-containing substance is 0.002 to 0.5 mol/L, It may be particularly preferable to set the amount to 0.005 to 0.1 mol/L.

(5) Hydroxycarboxylic acid-containing substance The chemical conversion treatment composition according to this embodiment contains a hydroxycarboxylic acid-containing substance. In the present specification, the hydroxycarboxylic acid-containing substance is composed of one or more types selected from the group consisting of hydroxycarboxylic acid, which is a carboxylic acid having a hydroxyl group, and a water-soluble substance containing a substance based on the hydroxycarboxylic acid. As the raw material for the hydroxycarboxylic acid-containing substance, it is preferable to use a water-soluble compound (hereinafter referred to as "water-soluble hydroxycarboxylic acid compound") that can be dissolved in water to produce a hydroxycarboxylic acid-containing substance. Water-soluble hydroxycarboxylic acid compounds also include esters that produce hydroxycarboxylic acids upon hydrolysis.

Examples of hydroxycarboxylic acids include 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. Examples include, but are not limited to. Water-soluble hydroxycarboxylic acid compounds also include salts and ions of these hydroxycarboxylic acids, such as sodium salts and potassium salts.

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. If the above molar concentration is less than 0.001 mol/L, the stability of the chemical conversion treatment composition may tend to decrease, and if it exceeds 5 mol/L, the load during wastewater treatment of the chemical conversion treatment composition increases. There are cases. From the viewpoint of appropriately ensuring the stability and wastewater treatment properties of the chemical conversion treatment composition, it may be more preferable that the hydroxycarboxylic acid equivalent molar concentration of the hydroxycarboxylic acid-containing substance is 0.002 to 5 mol/L. , 0.005 to 1 mol/L may be particularly preferable.

In the chemical conversion treatment composition according to the present embodiment, 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 is 1:1 to 1:10. By adjusting the molar concentration of the vanadium-containing substance and the molar concentration of the hydroxycarboxylic acid-containing substance within the above range, a chemical conversion film with a black appearance and high corrosion resistance can be stably obtained even if the cumulative treated area is large. .

(6) Nickel-containing substance, cobalt-containing substance The composition for chemical conversion treatment according to the present embodiment may contain one or more types selected from the group consisting of nickel-containing substances and cobalt-containing substances. The nickel-containing substance is composed of one or more types selected from the group consisting of water-soluble substances containing nickel, and includes nickel ions and complexes thereof. The cobalt-containing substance is composed of one or more selected from the group consisting of cobalt-containing water-soluble substances, and includes cobalt ions and complexes thereof. Nickel-containing substances contribute to blackening, and cobalt-containing substances contribute to improving corrosion resistance. It is desirable to use a compound (nickel compound, cobalt compound) that can produce a nickel-containing substance and a cobalt-containing substance in water as a raw material for the nickel-containing substance and the cobalt-containing substance.

Examples of nickel compounds include nickel chloride, nickel sulfate, nickel nitrate, nickel phosphate, nickel acetate, etc. The nickel compound may be composed of only one type of compound or may be composed of multiple types. Good too. Examples of cobalt compounds include cobalt chloride, cobalt sulfate, cobalt nitrate, cobalt phosphate, and cobalt acetate, and cobalt compounds may be composed of only one type of compound or may be composed of multiple types. Good too.

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

(7) Other components In addition to the above-mentioned substances, the chemical conversion treatment composition according to the present embodiment is 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 contain one or more types. It may further contain one or more selected from the group consisting of polymers such as waxes, corrosion inhibitors, surfactants, plastic dispersants, pigment forming agents such as dyes and pigments, drying agents, and dispersants. good. Further, a reducing substance may be added at the same time.

Metal ions include 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 ions are exemplified, and may exist in the form of oxygen acid ions. In addition, when the member (base material) to be chemically treated has a surface of a material containing zinc, as the cumulative treatment area increases, the zinc-containing substance (a water-soluble substance containing zinc) is added to the chemical conversion treatment composition. Specifically, zinc ions and their complexes are exemplified.) are accumulated. Generally, when the concentration of zinc-containing substances in a chemical conversion treatment composition increases in terms of zinc, it becomes difficult to maintain the black appearance of the chemical conversion coating. Since it is possible to obtain a black appearance even if the zinc content of the substance is 15 g/L, the zinc-containing substance may be contained within that range (15 g/L or less).

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. For example, it may contain phosphorus-containing inorganic acids 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.

The molar concentration of these inorganic acids and/or their ions in the chemical conversion treatment composition is not particularly limited. The total molar concentration of the inorganic acid and its ions can be from 0.1 to 10 as a ratio to the total molar concentration of trivalent chromium ions and the above metal ions (ions containing vanadium, nickel ions, cobalt ions, etc.). In some cases, it is preferable, and in some cases, 0.5 to 3 is more preferable.

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.

Nitrogen compounds include heterocyclic compounds, ureas, aliphatic amines, acid amides, aminocarboxylic acids, ammonium salts, urea, amines, organic nitrogen compounds such as nitrobenzenesulfonic acid, and nitrogen compounds such as urea, ammonium salts, and nitrates. The compounds are exemplified, and their preferred content is individually 0.5 to 50 g/L.

(8) Solvent The solvent of the chemical conversion treatment composition according to the present embodiment is mainly water, and from the viewpoint of stabilizing the contained components, a water-soluble organic solvent such as alcohol, ether, or ester may be mixed. good. Although the ratio of the organic solvent to the total solvent is not particularly limited, it may be preferably 10% by mass or less from the viewpoint of ensuring appropriate wastewater treatment properties.

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

(10) Overcoat After the chemical conversion treatment using the chemical conversion treatment composition according to the present embodiment, the corrosion resistance is further improved by washing with water and applying an inorganic, organic, or organic-inorganic composite coating before or after drying. Examples of inorganic overcoats include silica-based and phosphoric acid-based overcoats, and other overcoats are also possible. The organic overcoat is not limited to paints or resins, and may be water-based or non-aqueous. Organic coatings such as polyethylene, polyvinyl chloride, polystyrene, polypropylene, acrylic resin, methacrylic resin, polycarbonate, polyamide, polyacetal, fluororesin, urea resin, phenol resin, unsaturated polyester resin, polyurethane, alkyd resin, epoxy resin, melamine resin, etc. Examples include, but are not limited to. The overcoat may be performed immediately after drying after chemical conversion treatment, or after secondary processing such as bending or other molding, and there is no limit to the number of overcoats. The method of overcoating is not particularly limited, and various methods such as coating, dipping, electrostatic coating, electrodeposition, and powder coating are possible.

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

Hereinafter, the effects of the present invention will be explained based on Examples, but the present invention is not limited thereto. A phosphorus-containing compound containing an organic phosphonic acid compound is added to a chemical conversion treatment composition that contains an organic sulfur compound and can form a black film, and the vanadium-equivalent molar concentration of the vanadium-containing substance and hydroxycarboxylic acid of the hydroxycarboxylic acid-containing substance are determined. A chemical conversion treatment was carried out using a substance containing the acid in a molar concentration ratio of 1:0.5 to 1:10. When replenishing the chemical conversion treatment composition, changes in the appearance of the black film and changes in corrosion resistance were confirmed when the cumulative treated area was increased by quantitative replenishment. The chemical conversion treatment compositions used in the Examples were all so-called hexavalent chromium-free compositions that did not substantially contain hexavalent chromium.

(1) Preparation of composition for chemical conversion treatment First, compositions for chemical conversion treatment 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 values for chromium, nickel, and cobalt in the table are the content of chromium-containing substances in terms of chromium, the content of nickel-containing substances in terms of nickel, and the content of cobalt-containing substances in terms of cobalt, respectively, in the chemical conversion treatment composition. .

Further, in Table 4, chemical conversion treatment compositions having the composition of Patent Document 1 were prepared as comparative examples (Example 19 to Example 26). Furthermore, in Table 5, chemical conversion treatment compositions having the composition of Patent Document 2 were prepared as comparative examples (Example 27 and Example 28). The content of the transition metals (nickel, vanadium, manganese) used in the chemical conversion treatment compositions according to Examples 20 to 27 ranges from 0.1 to 0.1, which is the more preferable addition amount described in Patent Document 1. The median value of 10 g/L was set at 5 g/L.

(2) Preparation of test members Next, the electrogalvanized bolts were washed with water according to the usual method, and then immersed in nitric acid (3 mL/L solution of 67.5% nitric acid, liquid temperature at room temperature (25°C), immersion time 10 seconds) to activate the surface. This test member (base material) was further washed with water for 10 seconds at room temperature, 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 pulled out of the chemical conversion treatment composition was washed with water (room temperature, 10 seconds) and then dried at 80±5° C. for 10 minutes.

In addition, in Examples 19 to 26 (comparative examples) shown in Table 4, test members were immersed for 30 seconds in a chemical conversion treatment composition maintained at pH 2.0 and 30°C. In Example 27 and Example 28 (comparative example), the test member was immersed for 45 seconds in a chemical conversion treatment composition maintained at pH 2.2 and 35°C. The test member pulled out of the chemical conversion treatment composition was washed with water (room temperature, 10 seconds) and then dried at 80±5° C. for 10 minutes.

Surface treatment including the above chemical conversion treatment was performed on a large number of bolts, and when the cumulative treated area per 1L of the member obtained by the first chemical conversion treatment immediately after bath construction was 250, 500, 750, 1000 dm ² The test member obtained by the chemical conversion treatment was used as the test member for evaluation. The concentration of zinc ions contained in the chemical conversion treatment composition when the cumulative treated area per 1L is 500 ^dm2 is approximately 8 g/L, and the concentration of zinc ions contained in the chemical conversion treatment composition when the cumulative treated area per 1L is 1000 ^dm2 . The zinc ion concentration contained in the treatment composition was approximately 15 g/L.

(3) Replenishment method Since the components of the chemical conversion treatment composition decrease as the chemical conversion treatment progresses, quantitative replenishment was performed every time the treated area per liter increased by 100 dm ² . The supply amount was determined as follows. First, the composition for chemical conversion treatment is sampled when the treatment area reaches 100 dm ² per liter, and the chromium concentration is calculated using an ICP emission spectrometer ("ARCOS FH522" manufactured by SPECTRO) to determine the amount of chromium reduction in the sample. It was determined that each component of the chemical conversion treatment composition decreased at the same rate as this amount of chromium decrease, and the decrease amount of the chemical conversion treatment composition was calculated. As a specific example, if the amount of chromium reduced in the sample was 10% by mass when the treated area per 1L increased by ^100dm2 , it would be determined that each component of the chemical conversion treatment composition had decreased by 10% by mass, and the construction A composition having an amount 1/10 of the chemical conversion treatment composition used in the bath was replenished.

(4) Evaluation method 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 visually confirmed every 24 hours, and when the white rust area ratio reached 5% of the total, the accumulated salt water spray time of the test member was taken as the white rust generation time and used as an index of corrosion resistance.

The evaluation results are shown in Tables 6 and 7. The columns show the appearance and corrosion resistance based on the cumulative treated area per liter. As a specific example, if the time for 5% white rust to occur is 96 hours, and the appearance at this time is black, it is displayed as "black/96 hours."

Claims (7)

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. 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 from 1:1 to 1:10. The content of the trivalent chromium-containing substance is 1 to 10 g/L in terms of 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. The composition for chemical conversion treatment according to claim 1 or 2. The composition for chemical conversion treatment according to claim 1 or 2, which contains one or more types selected from the group consisting of nickel-containing substances and cobalt-containing substances. The composition for chemical conversion treatment according to claim 1 or 2, which contains a zinc-containing substance in an amount of 15 g/L or less in terms of zinc. A method for manufacturing a member provided with a chemical conversion film, the method comprising bringing the composition for chemical conversion treatment according to claim 1 or 2 into contact with a base material having a surface of a material containing zinc. 7. The manufacturing method according to claim 6, wherein the chemical conversion treatment composition is managed by quantitative supply.