JP4738747B2 - Black film agent and black film forming method - Google Patents

Description

  The present invention relates to an agent and a method for forming a hexavalent chromium-free black film on a zinc member, a zinc alloy member, a zinc-plated product, or a zinc alloy-plated product.

  In general, zinc or zinc alloy plating (for example, zinc-iron alloy plating, zinc-nickel alloy plating) is most widely used as a rust prevention method for ferrous materials and parts. However, since zinc is a rust-prone metal and white rust, which is the rust of zinc, is generated immediately when used as it is, it is generally common to form a protective film.

  The chromate film treatment is generally used as a protective film treatment usually applied to zinc plating or zinc-based alloy plating, and the chromate film treatment is further classified into three types: electrolytic chromate treatment, coating chromate treatment, and reactive chromate treatment. . The chromate treatment is applied not only to zinc but also to aluminum, cadmium and magnesium.

  Chromate film treatment is widely used because it is inexpensive and can easily obtain practical corrosion resistance. However, since all chromate film treatment uses harmful hexavalent chromium, it can be dissolved in not only the treatment solution but also the treated product. In recent years, chromium valence has been a major problem because it has adverse effects on the human body and the environment.

  Various inventions have been filed so far for solving the problem of pollution of hexavalent chromium. For example, Japanese Patent Application Laid-Open No. 52-92936, Japanese Patent Application Laid-Open No. 50-1934, and Japanese Patent Application Laid-Open No. 61-587. JP-A-2000-234177, JP-A-61-119677, and the like. Although these inventions can be noted in that no hexavalent chromium is used, practical performance is not satisfactory. For example, in the salt spray test stipulated in JIS Z 2731, the corrosion resistance that is stably exhibited is about 12 to 84 hours, which is only 1/20 to 1/2 or less of commonly used colored chromate and black chromate. Absent.

  As a specific problem, Japanese Patent Application Laid-Open No. 52-92936 treats zinc or a zinc alloy with an aqueous solution containing titanium ions and one or more of phosphoric acid, phytic acid, tannin and hydrogen peroxide. Although the invention characterized by this is disclosed, it is a treatment on a steel plate, and the corrosion resistance with salt spray is as low as about 240 hours even if the coating is baked after a complicated and high temperature treatment for a long time.

  JP-A-50-1934 discloses a colorless glossy chromate composition of zinc or zinc alloy, which comprises a mineral acid, a compound that generates trivalent chromium ions, a carboxylic acid, and, if necessary, a reducing agent. Yes. With this composition, it is possible to obtain a uniform gloss chromate appearance on zinc or a zinc alloy, but the corrosion resistance in salt spray is very low performance of 48 hours or less until the occurrence of white rust. The composition was poor in stability.

  Japanese Patent Application Laid-Open No. 61-587 describes a composition containing trivalent chromium ions, silicates, fluorides and acids. The coating obtained by this composition also has a uniform glossy chromate appearance, but the corrosion resistance is a low performance of 24 hours or less until white rust occurs.

  JP-A-2000-234177 discloses a chemical conversion treatment solution for zinc or zinc alloy comprising an aqueous solution containing a trivalent chromium compound and at least one metal compound selected from a titanium compound, a cobalt compound, a tungsten compound and a silicon compound. Is described. This treatment solution is expected to provide a conversion coating having a relatively high corrosion resistance, but there are large variations for practical use in industry, the treatment conditions are relatively high and long, and the drying temperature is also high. In addition to the high temperature and long time compared to the conventional method, the described treatment liquid has a problem of poor stability and precipitation in a few days. The resulting coating has a glossy chromate appearance like the others.

  JP-A-61-119677 discloses trivalent chromium ions, hydrogen ions, additional ions selected from iron, cobalt, nickel, molybdenum, manganese, aluminum, lanthanum, cerium, lanthanides and mixtures thereof; An acidic composition containing nitrate ions is described. In addition, compositions containing halogen ions, organic carboxylic acids or silicates are described. With this composition, it is possible to obtain a uniform gloss chromate appearance on zinc or a zinc alloy, but the corrosion resistance in salt spray was not sufficient, and white rust was generated for about 72 hours. In particular, a composition using an organic acid has poor liquid stability, and has a problem that the appearance of the treatment and the pH of the liquid change in several days to several weeks.

  The invention described in Japanese Patent Publication No. 63-015991 has environmental problems such as wastewater treatment because it contains fluorine in its components.

  Japanese Patent Application Laid-Open No. 2000-509434 also has an environmental problem because the component contains an organic acid.

  In addition, Japanese Patent Publication No. 03-010714 and Japanese Patent Application Laid-Open No. 2000-54157 have the same problems as described above, and these are also interference colors with a thin appearance and a black appearance can be obtained. Absent.

  Japanese Patent Application Laid-Open No. 2003-268562 discloses a method for obtaining a black appearance, because a chelating agent is included in the component, and this chelating agent forms a water-soluble complex with chromium, nickel, or cobalt and inhibits the formation of poorly soluble precipitates. In addition to environmental problems that would impede wastewater treatment, there were also problems such as lack of blackness, appearance problems such as unevenness, and insufficient corrosion resistance, which were not satisfactory.

  As described above, the conventional technologies generally have insufficient corrosion resistance, single appearance (weak interference colors such as glossy chromate, achromatic appearance), lack of stability, and cost performance (performance obtained for processing conditions). We had problems of lowness and environmental problems.

JP-A-52-92936 Japanese Patent Laid-Open No. 50-1934 Japanese Patent Laid-Open No. 61-587 JP 2000-234177 A JP-A-61-119677 Japanese Patent Publication No. 63-015991 JP 2000-509434 A Japanese Patent Publication No. 03-010714 JP 2000-54157 A JP 2003-268562 A

  An object of the present invention is to stably form a film having a uniform and good black appearance and corrosion resistance without using harmful hexavalent chromium in forming a protective film on the surface of metal, particularly zinc or zinc alloy. It is to provide a processing solution and method. In particular, it is to obtain excellent corrosion resistance, design properties, cost performance, and stability, which are obstacles to the practical application of alternative technologies that have been invented so far.

  As a result of intensive studies by the present inventors in order to solve the problems in the prior art, it is uniform even without using fluorine, organic acids, chelating agents, and phosphorus compounds that cause environmental problems in the prior art. It became possible to obtain a film with an excellent black appearance. Moreover, it discovered that the further external appearance improvement and the improvement of corrosion resistance can be aimed at by processing with a specific liquid composition after black film formation.

  The present invention relates to an anion group comprising (A) trivalent chromium and (B) sulfate ion, chlorine ion, chlorine oxyacid ion (for example, chloric acid, chlorous acid, hypochlorous acid and perchloric acid) and nitrate ion. Based on a liquid containing at least one selected from (C) and a sulfur compound, alkaline earth metals (including beryllium, magnesium, calcium, strontium, barium and radium are included for further improving the appearance and corrosion resistance. ), One or more metal ions selected from the group consisting of titanium, zirconium, vanadium, molybdenum, tungsten, manganese, iron, cobalt, nickel, gold, silver, copper, tin and aluminum, phosphorus or boron oxygen acids Ion (for example, phosphate ion, borate ion) and their salts, chelating agents, silicon compounds as appropriate, especially as metals Lucari earth metal, titanium, zirconium, vanadium, iron, cobalt, nickel, tin and aluminum are preferable. As chelating agents, monocarboxylic acids, dicarboxylic acids, tricarboxylic acids, hydroxycarboxylic acids, ammonia, amines, aminocarboxylic acids and the like. And the sulfur compound is preferably an organic sulfur compound. Moreover, the 2nd process liquid further processed after processing with this liquid contains 1 or more types of the group which consists of trivalent chromium, surfactant, and a silicon compound.

  As a specific concentration range, trivalent chromium is 0.1 to 30 g / L, preferably 0.5 to 20 g / L, and particularly preferably 1 to 10 g / L. 1 to 100 g / L, preferably 3 to 70 g / L, particularly preferably 10 to 45 g / L, and sulfate ions, chlorine ions, and oxyacid ions of chlorine are 0.05 to 80 g / L, preferably 0.1 To 50 g / L, particularly preferably 0.5 to 20 g / L, and the sulfur compound is 0.1 to 100 g / L, preferably 0.5 to 50 g / L, particularly preferably 1 to 20 g / L, Metal ions are 0.05 to 100 g / L, preferably 0.1 to 60 g / L, particularly preferably 0.5 to 20 g / L, and phosphorus and boron oxyacid ions are 0.05 to 80 g / L, Preferably 0.1-50g L, particularly preferably 0.5 to 20 g / L, chelating agent 0.05 to 70 g / L, preferably 0.1 to 50 g / L, particularly preferably 0.5 to 30 g / L, and silicon The compound is 0.2 to 100 g / L, preferably 1 to 70 g / L, particularly preferably 2 to 40 g / L. Regarding the second treatment liquid to be further treated, the trivalent chromium, the surfactant and the silicon compound are each 0.01 to 5 g / L, preferably 0.1 to 2 g / L. The other components are also thin and are generally 10% to 50% of the concentration used for the black film treating agent.

  If any component is less than these ranges, the effect cannot be obtained. On the other hand, if it is excessive, the effect reaches a peak, and not only is the economic loss large, but in some cases, excessive film formation is not preferable because it causes a decrease in corrosion resistance and a deterioration in appearance. If further added, the weight ratio of trivalent chromium to nitrate ion (nitrate ion / trivalent chromium) is 0.5 to 20, preferably 1 to 10, and the weight ratio of trivalent chromium to sulfur compound (sulfur compound / trivalent). Chromium) is 0.1 to 10, preferably 0.2 to 5, and the weight ratio of trivalent chromium to other metal ions (metal ion / trivalent chromium) is 0.01 to 5, preferably 0.1 When it is 3, it is possible to obtain a film having a more excellent appearance and excellent corrosion resistance.

  Various compounds containing trivalent chromium can be used as a source of trivalent chromium in the treatment liquid of the present invention. Specifically, in addition to salts such as chromium nitrate, chromium sulfate, chromium chloride, chromium phosphate and chromium acetate, compounds obtained by reducing hexavalent chromium compounds such as chromic acid and dichromate to trivalent with a reducing agent are used. It is also possible to do.

  The sources of nitrate ions, sulfate ions, chloride ions, chlorine oxyacid ions, phosphorus oxyacid ions and boron oxyacid ions can also be used as their own acids and salts thereof. Supplying it as a metal salt of other components such as trivalent chromium or supplying it with its own acid or sodium salt or magnesium salt is inexpensive and easily available from an industrial viewpoint. Among these anions, the most important anion is nitrate ion, which is effective in stability of corrosion resistance.

  Many compounds such as sodium sulfide, potassium sulfide, ammonium sulfide, calcium sulfide, sodium thiosulfate, and sodium hydrosulfide can be considered as the sulfur compound, and organic sulfur compounds are particularly preferable. Specifically, thioureas such as thiourea, allylthiourea, ethylenethiourea, diethylthiourea, diphenylthiourea, tolylthiourea, guanylthiourea and acetylthiourea, mercaptoethanol, mercaptohypoxatin, mercaptobenzimidazole and mercaptobenzthiazole Mercaptos, thiocyanic acid and salts thereof, amino compounds such as aminothiazole, etc., including Ouchi Shinsei Chemical Co., Ltd. Noxeller TMU, Noxeller TBT, Noxeller NS-P, Nocrack TBTU and Nocrack NS-10N, Kawaguchi Chemical Industries Accelerator 22-R, Accelerator 22-S, Accelerator BUR-F, Accelerator CZ, Accelerator EUR-H, Accelerator LUR, Accelerator TET, Accelerator TP, etc. are available. In addition, thiocarboxylic acids such as thioformic acid, thioacetic acid, thiomalic acid, thioglycolic acid, thiodiglycolic acid, thiocarbamic acid, thiosalicylic acid and their salts, dithioformic acid, dithioacetic acid, dithioglycolic acid, dithiodiglycolic acid, dithiocarbamine Dithiocarboxylic acids such as acids and salts thereof are useful because they have a skeleton similar to chelating agents.

  Among various metals, especially the addition of alkaline earth metals, titanium, zirconium, vanadium, iron, cobalt, nickel, tin and aluminum is effective in improving corrosion resistance and appearance, and also in molybdenum, iron, cobalt, By adding nickel, silver and copper, a black appearance can be easily obtained. These sources are not particularly limited, but generally nitrates, sulfates and chlorides are used.

  As the chelating agent, monocarboxylic acid, dicarboxylic acid, tricarboxylic acid, hydroxycarboxylic acid, ammonia, amine, aminocarboxylic acid and salts thereof can be used. Among these, carboxylic acids, in particular, oxalic acid, malic acid, malonic acid, oxalic acid, acrylic acid, formic acid, acetic acid, tartaric acid, citric acid, glutamic acid, ascorbic acid, inosinic acid, lactic acid and their salts have a uniform appearance. This is effective for increasing the thickness of the coating film and the film.

  As the silicon compound, sodium silicate, potassium silicate, lithium silicate, or colloidal silica having a particle size of 200 nm or less, more preferably colloidal silica having a particle size of 100 nm or less is preferable.

  The same supply source can be used for the second treatment liquid. In addition, one or more anions selected from the group consisting of sulfate ion, chlorine ion, nitrate ion, phosphorus oxyacid ion, chlorine oxyacid ion and boron oxyacid ion; alkaline earth metal, titanium, zirconium, Ions of one or more metals selected from the group consisting of vanadium, molybdenum, tungsten, manganese, iron, cobalt, nickel, gold, silver, copper, tin and aluminum; and monocarboxylic acids, dicarboxylic acids, tricarboxylic acids, hydroxy One or more chelating agents selected from the group consisting of carboxylic acids, ammonia, amines, aminocarboxylic acids and their salts; one or more may be selected, but if a plurality is supplied, salts Can be supplied at the same time. As for the surfactant, an appropriate amount of various commercially available surfactants may be used, and it can be used for fine adjustment of the friction coefficient depending on the surfactant type and concentration. As the surfactant, various surfactants can be used, and cationic surfactants are particularly preferable, and aliphatic amine salts, quaternary ammonium salts, and EO-added quaternary ammonium salts are more preferable. Specifically, Farmin, Cotamine, Sanisole (above trade name, Kao Corporation), Duomin, Armac, Arcard, Esocard (above trade name, Lion Corporation), Cation (trade name, Nippon Oil & Fats Co., Ltd.) And Adecamin (trade name, Asahi Denka Kogyo Co., Ltd.).

  It is also possible to apply a commercially available overcoat agent to these films. There are no particular limitations on the overcoat agent, and there are overcoat agents containing resins such as acrylic resins, epoxy resins, olefin resins, phenol resins, alkyd resins, melamine resins, silicates, and the like. More specifically, for example, Cosmar Coat (trade name, Kansai Paint Co., Ltd.), Triner TR-170 (trade name, Nippon Surface Chemical Co., Ltd.), Finigard (trade name, Coventya Co., Ltd.) and the like can be used.

  As a method of treating a zinc-based substrate using these treatment liquids, there is a method of bringing the substrate into contact with the treatment liquid once or a plurality of times. Types of galvanizing include a cyan bath, an acid bath, and a zincate bath, and zinc-alloy plating includes an acid bath and a zincate bath. Any of the baths can be used for plating, but a zincate bath, particularly preferably a zincate bath of a type excellent in throwing power is preferable (for example, Hyper Zincate (trade name): Nippon Surface Chemical Co., Ltd.). If necessary, the substrate to be treated is immersed in a thin nitric acid aqueous solution, hydrochloric acid aqueous solution, mixed acid aqueous solution or the like, and then the treatment according to the present invention is performed. Appropriate treatment liquid conditions include a liquid temperature of 10 to 70 ° C., preferably 15 to 60 ° C., particularly preferably 20 to 45 ° C., an immersion time of 10 to 120 seconds, preferably 15 to 90 seconds, and more preferably 25. -60 seconds, pH is 0.5-4.5, preferably 1.0-4.0, more preferably 1.5-3.0. The conditions of the second treatment liquid are such that the liquid temperature is 5 to 50 ° C., preferably 10 to 40 ° C., more preferably 15 to 35 ° C., the immersion time is 1 to 60 seconds, preferably 5 to 45 seconds, and more preferably. 10 to 35 seconds. In the case of trivalent chromium, the pH is 1 to 6, preferably 2 to 5. However, the surfactant and the silicon compound have an appropriate pH depending on the type, and may be acidic, neutral or alkaline. Further, in the case of overcoating these coatings, a method of bringing the substrate into contact with the treatment liquid once or a plurality of times, preferably a method of immersing, is adopted in the same manner as described above, but under the appropriate conditions of each overcoat agent. There is a need. In any step, it is preferable to perform proper liquid agitation and rocking of the processed material.

  In the present invention, a hexavalent chromium-free black film is formed on a zinc-based member. According to the present invention, it has become possible to obtain a coating having a uniform design-rich appearance and excellent corrosion resistance, which could not be obtained by conventional techniques, while reducing the burden on the environment.

  For example, since trivalent chromium has a low concentration, the amount of sludge generated during wastewater treatment is reduced, and loss due to liquid assembly can be suppressed. In addition, since fluorine, boron, organic acid, chelating agent, phosphoric acid, etc. are not essential components, the corresponding emission control items can be reduced, and coagulation inhibition is difficult to occur, so that actual wastewater treatment is easy. Compared with the case where it contained, it has many advantages, such as being able to reduce processing cost. In addition, it is excellent in stability over time, and there is no change in pH or change in appearance even after standing for 1 month, in order to maintain the performance equivalent to or higher than the coating treatment using hexavalent chromium which is the initial performance, It is possible to provide an extremely durable and practical treatment liquid that can save the trouble of renewing the liquid and can reduce the running cost by extending the life of the liquid.

  Up until now, the harmful effects of hexavalent chromium have been talked about, but it has been difficult to switch. Since many of the conventional problems have been solved by the present invention, it will be used in a wide range of fields in the future, and switching from hexavalent chromium will proceed.

  Hereinafter, the present invention will be described by way of examples. In the test, after performing appropriate pretreatment such as degreasing and acid dipping of the test piece, after applying either zinc plating (zincate) or zinc alloy plating (Strong Zinc; Nippon Surface Chemical Co., Ltd.), if necessary The treatment was performed after immersion in nitric acid. The plating film thickness was 8 to 10 μm in any plating. The corrosion resistance was evaluated by a salt spray test according to JIS Z 2371.

Example 1
A zinc-iron alloy plated product was treated with a treatment solution containing 15 g / L of chromium nitrate, 2 g / L of sodium nitrate, and 5 g / L of thioglycolic acid. The liquid temperature was 40 ° C., the immersion time was 55 seconds, and the pH was 2.2 under mild stirring. After lightly washing with water, drying was performed at 60 to 80 ° C. for 5 minutes. A glossy black film was obtained.

Example 2
The galvanized product was treated with a treatment solution containing chromium nitrate 25 g / L, cobalt nitrate 8 g / L, and thioglycolic acid 8 g / L. The liquid temperature was 35 ° C., the immersion time was 50 seconds, and the pH was 2.5 under mild stirring. After lightly washing with water, drying was performed at 80 to 100 ° C. for 5 minutes. A glossy black film was obtained.

Example 3
The galvanized product was treated with a treatment solution containing 15 g / L chromium nitrate, 5 g / L chromium sulfate, 5 g / L cobalt nitrate, 2 g / L nickel nitrate, and 10 g / L thioglycolic acid. The liquid temperature was 35 ° C., the immersion time was 45 seconds, and the pH was 1.8 under mild stirring. After lightly washing with water, drying was performed at 50 to 70 ° C. for 5 minutes. A glossy black film was obtained.

Example 4
The galvanized product was treated with a treatment solution containing 17 g / L of chromium nitrate, 8 g / L of cobalt nitrate, 2 g / L of nickel nitrate, and 5 g / L of sodium dithioglycolate. The liquid temperature was 28 ° C., the immersion time was 60 seconds, and the pH was 2.1 under mild stirring. After lightly washing with water, drying was performed at 60 to 80 ° C. for 10 minutes. A glossy black film was obtained.

Example 5
The galvanized product was treated with a treatment solution containing chromium nitrate 25 g / L, chromium sulfate 5 g / L, cobalt nitrate 15 g / L, thioglycolic acid 10 g / L, and oxalic acid 2 g / L. The liquid temperature was 35 ° C., the immersion time was 45 seconds, and the pH was 1.8 under mild stirring. After lightly washing with water, drying was performed at 50 to 70 ° C. for 5 minutes. A glossy black film was obtained.

Example 6
The galvanized product was treated with a treatment liquid containing chromium nitrate 22 g / L, cobalt nitrate 7 g / L, thiomalic acid 6 g / L, potassium dithiodiglycolate 5 g / L, colloidal silica 4 g / L, and sulfuric acid 1 g / L. The liquid temperature was 40 ° C., the immersion time was 40 seconds, and the pH was 2.2 under mild stirring. After lightly washing with water, drying was performed at 50 to 70 ° C. for 5 minutes. A glossy black film was obtained.

Example 7
Chromium nitrate 23 g / L, cobalt nitrate 6 g / L, thioglycolic acid 4 g / L, sodium dithiodiglycolate 4 g / L, oxalic acid 3 g / L, ammonia 1 g / L, sulfuric acid 1 g / L, 75% phosphoric acid 1 g / L The galvanized product was treated with a treatment solution containing. The liquid temperature was 35 ° C., the immersion time was 35 seconds, and the pH was 2.4 under mild stirring. After lightly washing with water, drying was performed at 50 to 70 ° C. for 5 minutes. A glossy black film was obtained.

Example 8
Chromium nitrate 23 g / L, cobalt nitrate 6 g / L, nickel sulfate 1 g / L, thioglycolic acid 4 g / L, sodium dithiodiglycolate 2 g / L, thiomalic acid 2 g / L, malonic acid 3 g / L, sulfuric acid 1 g / L The galvanized product was treated with a treatment liquid containing 4 g / L of colloidal silica. The liquid temperature was 25 ° C., the immersion time was 60 seconds, and the pH was 2.3 under mild stirring. After lightly washing with water, drying was performed at 50 to 70 ° C. for 5 minutes. A glossy black film was obtained.

Example 9
Chromium nitrate 23g / L, chromium sulfate 3g / L, cobalt nitrate 6g / L, nickel sulfate 1g / L, thioglycolic acid 4g / L, ammonium dithioglycolate 3g / L, sulfuric acid 1g / L, colloidal silica 4g / L The galvanized product was treated with the treating solution. The liquid temperature was 35 ° C., the immersion time was 50 seconds, and the pH was 2.2 under mild stirring. After lightly washing with water, drying was performed at 80 to 100 ° C. for 10 minutes. A glossy black film was obtained.

Examples 10-13
After being treated with the treatment liquids of Examples 3, 5, 7, and 9 and washed with water, they were further immersed in a 25 ° C. aqueous solution of pH 3.8 containing 0.5 g / L of trivalent chromium for 20 seconds without drying. These were dried, and it was set as Examples 10, 11, 12, and 13 in order. Compared with Examples 3, 5, 7, and 9, the gloss was further increased and a uniform appearance was obtained.

Examples 14-17
After treating with the treatment liquids of Examples 3, 5, 7, and 9 and washing with water, the samples were further immersed in a 30 ° C. aqueous solution of pH 9 containing 2 g / L of colloidal silica for 20 seconds, and then dried. In Example 14, 15, 16, and 17. Compared with Examples 3, 5, 7, and 9, the gloss was further increased and a uniform appearance was obtained.

Examples 18-21
After being treated with the treatment liquids of Examples 3, 5, 7, and 9 and washed with water, the solution was further dried in a 20 ° C. aqueous solution of pH 3.9 containing 2.5 g / L of chromium nitrate and 1 g / L of cobalt nitrate without drying. After dipping for a second, each was dried and in order of Examples 18, 19, 20, and 21. Compared with Examples 3, 5, 7, and 9, the gloss was further increased and a uniform appearance was obtained.

Examples 22-30
The test pieces of Examples 1, 2, 4, 6, 8, 10, 11, 12, and 13 were further immersed in Cosmer NC (trade name) at 23 ° C. for 20 seconds and then dried, and Examples 22, 23, and 24, respectively. 25, 26, 27, 28, 29, 30. A very glossy black appearance was obtained.

Comparative Example 1
The galvanized product was treated with a commercially available black chromate agent (MB-342A (trade name, Nippon Surface Chemical Co., Ltd.); 200 ml / L, black B; 10 ml / L; containing about 2 g / L of hexavalent chromium). The liquid temperature was 30 ° C., and the treatment time was 90 seconds under mild stirring. After lightly washing with water, drying was performed at 80 to 100 ° C. for 10 minutes. A glossy black film was obtained.

Comparative Example 2
The galvanized product was treated with a treatment solution containing 50 g / L of chromium chloride hexahydrate, 3 g / L of cobalt nitrate, 100 g / L of sodium nitrate, and 31.2 g / L of malonic acid. The liquid temperature was 30 ° C., the immersion time was 40 seconds, and the pH was 2.0, with gentle stirring. After lightly washing with water, drying was performed at 80 to 100 ° C. for 10 minutes.
The obtained film was an interference color, and a glossy black film was not obtained.

Comparative Example 3
Trivalent chromium 2g / L, nitrate ion 0.4g / L, phosphate ion 12g / L, sulfate ion 2g / L, malonic acid 12g / L, cobalt 1g / L, nickel 0.5g / L, silicon 1g / L The galvanized product was treated with the treating solution. The solution temperature was 30 ° C., the immersion time was 60 seconds, and the pH was 2.5 under mild stirring. After lightly washing with water, drying was performed at 80 to 100 ° C. for 10 minutes. A blackish film with weak interference was obtained.

[Salt spray test]
Corrosion resistance of the test pieces of Examples 3, 5, 7, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21 and Comparative Examples 1, 2, 3 and salt spray test It was evaluated by. In Comparative Example 2, after 72 hours, Examples 3, 5, 7, and 9 and Comparative Examples 1 and 3 showed white rust generation of 5% with respect to the surface area of the test piece after 120 hours. In Examples 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, and 21, 5% white rust was observed after 168 hours. In Examples 22, 23, 24, 25, 26, 27, 28, 29, and 30, white rust did not occur even after 168 hours, or less than 5%. Even if hexavalent chromium was not used, corrosion resistance equivalent to or better than the coating treatment using hexavalent chromium could be obtained.

[Stability test]
Examples 1, 3, 5, 7, 9, and 11 and Comparative Examples 2 and 3 were allowed to stand at room temperature (about 25 ° C.) for 1 month. In all the comparative examples, the pH decreased by 0.3 or more in 3 or 4 days. The test piece treated with the liquid one week later had a non-uniform appearance with unevenness, and the corrosion resistance by spraying with salt water had decreased to 72 hours or less until the occurrence of 5% white rust. The treatment liquids of the examples showed no change in pH, appearance, and corrosion resistance even after being left for one month.

Claims (6)

(A) at least one selected from the group consisting of trivalent chromium and (B) sulfate ions, chlorine ions, chlorine oxyacids and nitrate ions, (C) an organic sulfur compound, and (D) a particle size Including colloidal silica of 200 nm or less,
A hexavalent chromium-free black coating solution for surface treatment of zinc plating or zinc alloy plating formed in a zincate bath, further comprising at least one selected from the group consisting of phosphorus oxyacid ions and boron oxyacid ions.   Furthermore, it contains ions of one or more metals selected from the group consisting of alkaline earth metals, titanium, zirconium, vanadium, molybdenum, tungsten, manganese, iron, cobalt, nickel, gold, silver, copper, tin and aluminum. The treatment liquid according to 1.   Furthermore, the processing liquid of Claim 1 or Claim 2 containing a chelating agent.   The processing solution according to claim 3, wherein the chelating agent is at least one selected from the group consisting of monocarboxylic acids, dicarboxylic acids, tricarboxylic acids, hydroxycarboxylic acids, ammonia, amines, aminocarboxylic acids and salts thereof.   The metal ion is one or more selected from the group consisting of metal ions of alkaline earth metals, titanium, zirconium, vanadium, iron, cobalt, nickel, tin, and aluminum. The processing liquid as described. A zinc member, a zinc alloy member, a zinc-plated product, or a zinc alloy-plated product each formed in a zincate bath is brought into contact with the treatment liquid according to any one of claims 1 to 5 once or a plurality of times. A method of forming a hexavalent chromium-free black film characterized by