JP2006022364A - Treatment agent for forming protective film on metal, and forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a uniform and protective film which does not contain such a substance as to form detectable harmful hexavalent chromium, and has both adequate appearance and adequate corrosion resistance, on the surface of zinc or a zinc alloy, and to satisfy the corrosion resistance, design characteristics and a cost performance, which are bottlenecks for a replaceable technology such as a conventional trivalent-chromium-based rust preventive film to be commercialized. <P>SOLUTION: This treatment agent has a liquid composition comprising: (A) a trivalent chromium ion; (B) one or more anions selected from the group consisting of a chlorine ion, a fluorine ion, a sulfate ion and a nitrate ion; (C) one or more elements selected from the group consisting of Ni, Pd, Pt, Sc, Y, V, Nb, Ta, Cu, Ag and Au; and (D) one or more compounds selected from the group consisting of Si, Al, a compound thereof and an organic acid. The rust preventive film is formed by using the liquid composition. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention is intended to protect various metals, but particularly relates to rust prevention of zinc or zinc alloys and metal materials plated with these metals, and particularly iron coated with zinc and zinc-based alloys. The present invention relates to a liquid rust inhibitor used for rust prevention of parts and rust prevention using the same.

In general, zinc or zinc-based alloy plating (hereinafter referred to as zinc plating) is most widely used as a rust prevention method for ferrous materials and parts. However, when a galvanized iron-based material / part is used as it is, white rust, which is rust of zinc, is immediately generated, and therefore a protective film is usually further formed.
A chromate film treatment is generally used as a protective film usually applied to galvanizing, 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, magnesium and the like.

  Chromate coatings are widely used because they are inexpensive and easily obtain practical corrosion resistance, but all chromate treatment uses harmful hexavalent chromium, so hexavalent chromium that dissolves not only from the treatment solution but also from the treated product. However, it has become a big problem in recent years because it has a bad influence on the human body and the environment. This is a problem that cannot be solved as long as the chromate film is a film that exhibits corrosion resistance due to hexavalent chromium in the film.

  Various inventions have been filed so far for solving the problem of pollution of hexavalent chromium. For example, Japanese Patent Laid-Open Nos. 52-9236, 50-1934, 61-587, 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 H 2731, the corrosion resistance that is stably exhibited is around 12 to 84 hours, which is only 1/20 to 1/2 or less of commonly used colored chromate and black chromate. Absent.
Further, since these films do not have the ability to suppress deterioration of corrosion resistance at the time of film damage, which is called self-repairing property, when the test piece is damaged by cross-cutting or extrusion / bending with a knife, the corrosion resistance in JIS Z2731 is 24. There is only less than an hour.
As a further serious problem, these costs are 5 to 10 times that of conventional colored chromate, and it may be difficult to establish industrially.

  As a specific problem, Japanese Patent Laid-Open No. 52-92936 treats zinc or a zinc alloy with an aqueous solution of one or more selected from the group consisting of Ti and phosphoric acid, phytic acid, tannic acid or hydrogen peroxide. It is characterized by doing. Even if the coating is baked after being processed on a steel plate for a complicated and high temperature for a long time, the corrosion resistance in salt spray is about 240 hours, which is low.

  JP-A-50-1934 describes a colorless glossy chromate composition of zinc or a zinc alloy comprising a mineral acid, a compound that generates trivalent chromium ions, a carboxylic acid, and optionally a reducing agent. 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 discloses a composition containing trivalent chromium ions, silicate, fluoride and acid. The film obtained by this composition also has a uniform gloss chromate appearance, and the corrosion resistance is a low performance of 24 hours or less until white rust occurs.

  Japanese Patent Application Laid-Open No. 2000-234177 describes a chemical conversion treatment solution for zinc or zinc alloy comprising a trivalent chromium compound and a titanium compound, a cobalt compound, a tungsten compound and a silicon compound. This treatment solution is expected to provide a chemical film with relatively high corrosion resistance, but there are large variations for practical use in industry, the treatment conditions are relatively high for a long time, and the drying temperature is higher than before. In addition to the long time, the described treatment liquid has a problem of poor stability and precipitation in a few days. The resulting film has a glossy chromate appearance like the others.

  JP-A-61-119677 describes an acidic composition containing trivalent chromium and iron, cobalt, nickel, molybdenum, manganese, aluminum, lanthanum, cerium, lanthanide, a mixture thereof, and nitric acid. Furthermore, compositions containing organic carboxylic acids and 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.

  As described above, conventional technologies generally lack corrosion resistance, single appearance (weak interference colors such as glossy chromate, achromatic appearance), lack of stability, and cost performance (low performance obtained with respect to processing conditions). Had the problem of low.

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

  The object of the present invention is to stably produce a film having uniform and good 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 in. In particular, it is to obtain excellent corrosion resistance, design properties, and cost performance, which are obstacles to the practical application of alternative technologies that have been invented so far.

  As a result of intensive studies conducted by the present inventors in order to solve the problems in the prior art, it has never been achieved by properly blending a specific group composed mainly of various metals and arranged in an appropriate combination. It has been found that excellent corrosion resistance, design properties and cost performance are obtained.

  Furthermore, after forming a rust preventive film with a liquid composition, by forming a protective film with a liquid composition containing one or more selected from the group consisting of silicon, resin, and wax, the above-described further improvement in characteristics can be achieved. In addition, it has been found that the friction coefficient can be controlled.

  That is, 0.01-150 g / L, preferably 0.1-50 g / L of trivalent chromium ions, 0.05-200 g / L, preferably 0.1-100 g / L of chlorine, fluorine, sulfate ions, One or more of nitrate ions and 0.001 to 200 g / L, preferably 0.01 to 50 g / L of Ni, Pd, Pt, Sc, Y, V, Nb, Ta, Cu, Ag, Au, Zn A method of forming a rust-preventing film with a liquid composition containing at least one species and 0.1 to 300 g / L, preferably 0.5 to 100 g / L of Si, Al, compounds thereof, and one or more organic acids In addition, by forming a protective film with a liquid composition containing at least one of Si, oxides thereof, resins, and waxes, corrosion resistance equivalent to or higher than that of conventional colored chromate can be obtained. The appearance of the non-appearance, such as the door was found to be also obtained.

  If any component is less than these ranges, the effect cannot be obtained. On the other hand, if the amount 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. If further added, the ratio of the group consisting of trivalent chromium and Ni, Pd, Pt, Sc, Y, V, Nb, Ta, Cu, Ag, Au, Zn is 1: 500 to 1: 0.0002, preferably 1:30 to 0.002, the ratio of the group consisting of trivalent chromium and Si, Al, their compounds and organic acids is 1: 1000 to 1: 0.01, preferably 1:10 to 1: 0.02. Then, a more excellent corrosion resistant film can be obtained stably.

  Furthermore, if a combination is selected, the combination of trivalent chromium and Ni, Pd, Pt, Sc, V, Nb, Ta, Au and Si, its compound, organic acid, and acid is particularly high. It tends to show corrosion resistance.

  There is no particular designation for the method of supplying any metal, and other necessary components such as acids can be obtained by supplying organic salts, oxoacids, oxoacid salts, etc. in addition to inorganic salts such as chlorides, sulfates and nitrates. It is convenient because ions and the like can be supplied. In particular, sulfuric acid compounds and nitric acid compounds have good corrosion resistance. In addition to these, Si and Al can be supplied as oxides or colloidal oxides. Moreover, adding a stabilizer to the liquid composition is effective for stabilizing the corrosion resistance and the design. Stabilizers include 0.1-100 g / L, preferably 0.5-50 g / L surfactant, hydrogen peroxide, heterocyclic compounds, aliphatic amines, acid amides, aminocarboxylic acids, ammonium salts, fats Aromatic sulfonic acids and aromatic aldehydes are effective. Particularly preferred are nitrogen-containing compounds such as heterocyclic compounds, ureas, aliphatic amines, acid amides, aminocarboxylic acids and ammonium salts, and nitrogen-containing surfactants.

  The content of Si and Al for forming the protective film is 0.001 to 500 g / L, preferably 1 to 300 g / L. If the amount is insufficient, the effect cannot be obtained. May occur. In any of the rust preventive coating and the protective coating, the silicon compound is preferably sodium silicate, potassium silicate, lithium silicate, or colloidal silica having a particle size of 100 nm or less, more preferably 50 nm or less. As the aluminum compound, aluminum sulfate, aluminum chloride, alumina sol, aluminum stearate, aluminum silicate and the like are preferable.

  The resin is not particularly defined, but among them, Teflon resin, epoxy resin film, acrylic resin film, melamine resin, acrylic silica resin, and acrylic Teflon resin are preferable. It is necessary to select an appropriate concentration depending on the corrosion resistance and appearance (gloss, puddle, unevenness), etc., and 1 to 800 g / L, preferably 10 to 500 g / L, tends to obtain high corrosion resistance.

Examples of the organic acid include carboxylic acids such as oxalic acid, malic acid, malonic acid, oxalic acid, acrylic acid, formic acid, acetic acid, tartaric acid, citric acid, glutamic acid, ascorbic acid, inosinic acid, and lactic acid. The content is 0.1 to 500 g / L, preferably 1 to 200 g / L. When the amount is insufficient, the effect cannot be obtained. When the amount is excessive, the effect reaches a peak, resulting in an increase in economic loss and a poor appearance.
There are various types of wax, but petroleum wax, polyurethane wax, polyethylene wax, polypropylene wax, and polyacrylic ester are preferable. Although it cannot be specified unconditionally depending on the required characteristics (friction coefficient, etc.), generally it can be used with little influence on other characteristics if it is in the range of 0.01 to 200 g / L.

  Moreover, as a preferable process condition of rust prevention film preparation by a liquid composition, process time 5-90 second, process temperature 10-80 degreeC, pH 1-4, More preferably, process time 15-60 second, process temperature 25-40 ° C and pH 1.5-3. As preferable treatment conditions for the protective film containing Si or the like, a treatment time of 1 to 60 seconds, a treatment temperature of 5 to 80 ° C., a pH of 7.5 to 14, more preferably a treatment time of 10 to 40 seconds, a treatment temperature of 15 to 60 ° C., The pH is 8 to 13, and the processing temperature is 10 to 30 ° C. depending on the resin.

  Protective coatings obtained by these combinations not only provide corrosion resistance equal to or higher than that of colored chromate, but also proved to be a practical protective coating with the ability to suppress corrosion resistance degradation when the coating is damaged. did. This anti-corrosion ability is a thing that suppresses the occurrence of rust at the time of film damage caused by stepping stones in automobile parts, etc., and is a performance that was hardly obtained in the invention so far, but an extremely important industrial performance It is. In addition, a uniform color tone that could not be obtained in the past can be obtained, and the design is improved.

  This method can perform treatment at a high temperature of 40 to 80 ° C. and a relatively long time of 45 to 90 seconds. However, depending on the application, the economical merit that a conventional reactive chromate treatment facility can be used as it is also of this method. It is also a feature. The treatment conditions for forming the film can be the same as the conventional chromate treatment conditions (liquid temperature 20 to 35 ° C., treatment time 20 to 40 seconds, with stirring), and a protective film made of a composition containing silicon, resin and wax. The treatment conditions for the production may be simply immersed at a liquid temperature of 20 to 50 ° C. for 20 to 40 seconds, and a series of treatments are very easy.

(Function)
By using the acidic aqueous solution specified in the present invention, no harmful hexavalent chromium is used, and a strong insoluble film is formed on the zinc surface with the same processing equipment, processing conditions and processing methods as conventional reactive chromate. Is possible. As a result, not only general users who are worried about elution of hexavalent chromium from the treated product, but also health effects and effects on wild animals of chromate manufacturers and chromate treatment companies that have been exposed to the harmful effects of chromic acid. It becomes possible to solve the problem.

  The trivalent chromium-containing composition selected from the four groups described in the present invention not only solves the pollution problem of hexavalent chromium, but also at the time of damage to the film, which is difficult to obtain with conventional alternative techniques. It also becomes possible to provide corrosion inhibition capability. That is, conventionally, the prevention without using hexavalent chromium such as JP-A-52-92936, JP-A-50-1934, JP-A-61-587, JP-A-2000-234177, JP-A-61-119677, etc. Rust films have been proposed.

  However, these films do not have the self-healing ability referred to in the conventional chromate film or are very weak. Therefore, when the film is damaged, the corrosion resistance in the salt spray test is about 24 to 72 hours, which is not practical. In addition, a lot of things with moderate weight such as bolts are dropped or collided with each other (co-displacement during processing). The line did not perform well. In some cases, the composition lacks the stability of the treatment liquid.

  In JP-A No. 2003-313675, the ability to suppress a decrease in corrosion resistance at the time of film damage is also added, but there are many essential components and Co is described, and JP-A No. 2003-166075 also discloses a Co-containing trivalent chromium treatment agent. Is described.

The hexavalent chromium-free chemical conversion coating on zinc plating or zinc alloy plating, which has started to be distributed in the market due to environmental problems, is a combination of trivalent chromium treatment containing Co in order to give the ability to suppress the deterioration of corrosion resistance when the coating is damaged. Is often used. Co-containing trivalent chromium treating agents have come to be used even in actual factory lines, and conversion and combination of hexavalent chromate to Co-containing trivalent chromium treating agents has been conventionally performed.
However, when the hexavalent chromate treatment solution and the Co-containing trivalent chromium treatment solution are simultaneously treated in the factory line, the time elapses when sodium bisulfite, Co, and trivalent chromium used as the hexavalent chromium reducing agent are mixed. At the same time, new problems such as detection of hexavalent chromium were confirmed.

Since Co is not used in the present invention, these problems in wastewater treatment are also solved. In the present invention, as a result of investigation, it was confirmed that sufficient rust prevention ability was obtained even if Co was not contained. Although the detailed reaction mechanism has not been clarified, each of the four components in this patent does not provide the ability to suppress corrosion resistance degradation when the film is damaged. It was found that the ability to suppress corrosion resistance reduction can be obtained.
Furthermore, the present invention not only provides higher corrosion resistance but also improves the cost performance and allows the friction coefficient to be controlled by adding wax or the like.

Hereinafter, the present invention will be described by way of examples.
In the test, after performing appropriate pretreatment such as degreasing and nitric acid immersion on the test piece, either zinc plating (Zn), zinc-iron alloy plating (Zn / Fe), or zinc-nickel alloy plating (Zn / Ni) Used after applying. The thickness of the plating was 8-9 μm for any plating.
Evaluation shows the time which white salt rust generate | occur | produced by performing the salt spray test according to JISZ2301. Unless otherwise specified, no changes were observed in the liquid appearance, pH, and treated appearance after standing for 1 week.

  From the results shown in the table, the present invention was able to provide a protective film that imparts corrosion resistance equivalent to that of conventional chromate treatment with hexavalent chromium by a synergistic effect by combining all four types of components (A to D). It is. Moreover, sufficient corrosion resistance cannot be obtained if one or two kinds of components essential to the present invention are lacking as in Comparative Examples 2 to 7, but according to the present invention, Comparative Examples 1, 8, and 9 (hexavalent chromium is added). Excellent corrosion resistance equivalent to or better than that of the conventional example of use) can be obtained.

Claims (10)

  (A) one or more members selected from the group consisting of trivalent chromium ions, (B) chlorine, fluorine, sulfate ions and nitrate ions, (C) Ni, Pd, Pt, Sc, Y, V, Nb, Ta, A rust preventive film is formed from a liquid composition containing one or more members selected from the group consisting of Cu, Ag, and Au, and (D) one or more members selected from the group consisting of Si, Al, compounds thereof, and organic acids. A method for forming a protective film of a metal.   The method for forming a protective film for a metal according to claim 1, wherein the film is formed with a liquid composition containing a stabilizer.   3. A method for forming a protective film of a metal, characterized in that, after carrying out the process of claim 1 or 2, the metal composition is further treated with a liquid composition containing at least one of the group consisting of Si, resin and wax.   The metal protective film forming method according to claim 1, wherein the metal is zinc, aluminum, magnesium, copper, nickel, chromium, iron, tin, or an alloy thereof.   (A) one or more members selected from the group consisting of trivalent chromium ions, (B) chlorine, fluorine, sulfate ions and nitrate ions, (C) Ni, Pd, Pt, Sc, Y, V, Nb, Ta, A metal composition characterized by comprising a liquid composition containing one or more members selected from the group consisting of Cu, Ag, and Au, and (D) one or more members selected from the group consisting of Si, Al, compounds thereof, and organic acids. Protective film forming agent.   6. The metal protective film-forming agent according to claim 5, wherein the film is formed with a liquid composition containing a stabilizer.   A combination of the liquid composition for forming a protective film of a metal, comprising a combination of the liquid composition according to claim 5 or 6 and a liquid composition containing at least one of the group consisting of Si, a compound thereof, a resin, and a wax. .   The metal protective film-forming agent according to any one of claims 5 to 7, wherein the metal is selected from zinc, aluminum, magnesium, copper, nickel, chromium, iron, tin, and alloys thereof.   The composition is (A) 0.01 to 150 g / L of trivalent chromium ions, (B) 0.05 to 200 g / L of chlorine, fluorine, sulfate ions, or nitrate ions, and (C) 0.001 to 200 g / L of Ni, Pd, Pt, Sc, Y, V, Nb, Ta, Cu, Ag, Au, one or more kinds of Zn, (D) 0.1 to 300 g / L of Si, The method of Claim 1 containing Al, those compounds, and 1 or more types of organic acid.   The composition is (A) 0.01 to 150 g / L of trivalent chromium ions, (B) 0.05 to 200 g / L of chlorine, fluorine, sulfate ions, or nitrate ions, and (C) 0.001 to 200 g / L of Ni, Pd, Pt, Sc, Y, V, Nb, Ta, Cu, Ag, Au, one or more kinds of Zn, (D) 0.1 to 300 g / L of Si, The metal protective film-forming agent according to claim 5, comprising Al, a compound thereof, and one or more organic acids.