JP2008121101A - Rust-preventing liquid for metal surface plated with zinc or zinc alloy, and method for forming rust-preventing film on the metal surface - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chromium-free rust-preventing liquid which gives a high rust-preventing power and adequate appearance onto a metal surface plated with zinc or a zinc alloy in any main galvanizing bath type, through a process similar to a conventional chromate conversion process or a process with the use of a trivalent chromium conversion liquid, and to provide a method for forming a rust-preventing film on the metal surface. <P>SOLUTION: The method for forming the rust-preventing film having both of the high rust-preventing power and adequate appearance with various types of colors so as to give the improved rust-preventing power onto the metal surface plated with zinc or the zinc alloy includes forming the rust-preventing film with a structure comprising two layers or more. The first layer containing mainly metal ions is formed in an activation step with the use of nitric acid, which is the first step of rust-preventing film treatment after the plating process using zinc or the zinc alloy. Subsequently, the second layer of the rust-preventing film is formed. The rust-preventing liquid therefor does not contain chromium. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

Detailed Description of the Invention

In the process of forming a rust preventive film on a zinc or zinc alloy-plated metal surface, the present invention provides chromium-free metal ions and phosphorus that can form a rust preventive film in the first layer simultaneously with the activity of nitric acid as the first process. By forming a rust-preventing film mainly composed of acid ions at the same time, and then forming a chromium-free second-layer rust-preventing film, a single layer of rust-preventing film can be used to achieve a sufficient anti-rust effect. The present invention relates to a method for producing a colorless or colored chrome-free rust-proof coating that improves the rust-proofing effect by generating a multi-layer rust-proof coating.

Conventionally, in order to improve rust prevention and decoration on a metal surface plated with zinc or zinc alloy, a method of forming a rust prevention film with a treatment solution containing hexavalent chromium, that is, a chromate method is generally performed. I have been.

However, hexavalent chromium is feared to affect the human body and the environment, and the EU has banned the use of hexavalent chromium. In Japan, studies are proceeding in the direction of eliminating parts using hexavalent chromium from home appliances and automobile parts.

As an alternative technology to hexavalent chromium, there is a method for producing a rust-preventing film containing trivalent chromium, but as an impurity in the trivalent chromium salt as a raw material for producing an anti-corrosive treatment liquid of trivalent chromium. Considering that it is difficult to completely remove hexavalent chromium and that there is a concern about natural oxidation of trivalent chromium compounds to hexavalent chromium compounds in the produced rust-preventive coating, etc. In discussing the contamination problem, complete hexavalent chromium-free is difficult as long as trivalent chromium salts are used. Therefore, there is a possibility that trivalent chromium will be subject to regulation in the near future.

Examples of surface treatment methods that do not use chromium at all, so-called chromium-free treatment methods, include, for example, phosphate films (Japanese Patent Laid-Open No. 2001-591824), oxalate films, and films using metal salts using electrolysis (Japanese Patent Laid-Open No. 2001-2001). 247777) and organic resin films (Japanese Patent Laid-Open No. 2000-290782) have been proposed, but there are many points that are insufficient in corrosion resistance, the processing temperature is high, and the process is complicated. There are problems such as being difficult to use, and there are many cases that have not been put into practical use.

Problems to be solved by the invention

As described above, the chromium-free treatment methods proposed up to now have many problems as described above, and the existing facilities in the zinc or zinc alloy plating plant require a large remodeling. Must. Therefore, corrosion resistance and adhesiveness that enable chromium-free rust-proofing treatment without major modifications to the conventional chromate method equipment, excellent processing temperature is near room temperature, and processing time is close to chromate processing. Development of a treatment method and a rust preventive treatment liquid is strongly desired.

Another problem in this development is that conventional electrogalvanizing mainly includes a cyan bath, a zincate bath, and a chlorination bath. It is said that chromium-free rust prevention technology that can handle all major bath types is difficult due to the different properties of certain zinc compounds. Therefore, it is necessary to develop a rust-proofing solution that can handle all of these main types of galvanizing baths.

As for the conventional anticorrosive film formation on zinc or zinc alloy plating, the chromate method is the mainstream, and as the method of forming the anticorrosive film, first activation with dilute nitric acid after zinc plating (several seconds to 10 seconds) After passing through a water washing step, the substrate is immersed (6 to 60 seconds) in the chromate treatment solution in the reaction tank, washed with water, proceeds to the drying step, and is often commercialized. Also, in the trivalent chromium treatment solution method, which is an alternative technology to the chromate method, after activation with dilute nitric acid (several seconds to 10 seconds), it is immersed in the trivalent chromium treatment solution in the reaction vessel ( 30 seconds to 60 seconds), and after washing with water, the process proceeds to a drying process and is often commercialized. That is, at present, as for the facilities of the galvanizing / rust prevention processing plant, those designed along the above-mentioned processes are mainly used.

Further, in the conventional chromate method and trivalent chromium treatment liquid method, the treatment temperature is usually a room temperature treatment of about 15 ° C. to 35 ° C., and there is often no equipment design for high temperature treatment. .

Therefore, it is possible to form chromium-free coatings with existing rust prevention treatment equipment, and the technological development of economical rust prevention treatment liquids and treatment methods will quickly bring chrome free in Japan. It is considered necessary to push forward.

Means for solving the problem

が図れる。すなわち、従来のクロメート法で行なわれている装置を大きく改造することなしに、耐食性のある複層のクロムフリーの防錆皮膜を生成させることが可能となる。When forming a chromium-free coating on the metal surface of zinc or zinc alloy plating, the rust prevention effect of the second layer is not sufficient with a single layer of the first layer of rust prevention coating. Raw film

Can be planned. That is, it is possible to generate a corrosion-resistant multilayer chromium-free rust-proof film without greatly modifying the apparatus used in the conventional chromate method.

That is, when a colorless or colored rust preventive film is formed on a zinc or zinc alloy plated metal surface, a complex film such as a phosphate film containing metal ions is plated on the first rust preventive film layer. It is formed with zinc or zinc alloy, and has a rust prevention effect. However, this single layer alone does not have a sufficient rust prevention effect. By using a treatment solution containing tannic acid, a second rust preventive film can be formed, and these two layers of rust preventive films can form a chromium-free rust preventive film having sufficient rust preventive power. it can. In addition, this process is almost the same process as the current chromate method or trivalent chromium treatment solution method in the galvanization / rust prevention treatment plant, so the first rust prevention coating layer is activated when activated. By using a method such as forming a rust-proof coating solution, it is easy to replace the rust-proof coating treatment solution without major modifications to the rust-proofing equipment currently owned by most galvanizing and rust-proofing plants. It is possible to form a chromium-free rust-proof film having a sufficient rust-proof effect.

The invention's effect

In the rust prevention treatment after galvanization, the process called activation with dilute nitric acid cleans the surface of the galvanized product by dissolving the zinc in the galvanized layer with dilute nitric acid, and This brings about an effect of giving an environment in which a rust preventive film is easily generated. In the activation process, the present invention includes at least one kind of metal ions of Al, Ti, V, Mn, Ni, Cu, Co, Mo, W, and Zr, which have a rust preventive effect on the zinc surface simultaneously with activation. It is a mixture, and these metal ions combine with the plated zinc, and can produce a rust preventive film having excellent rust preventive property of the first layer which cannot be achieved by general nitric acid activation.

In the present invention, when producing a colorless or colored rust preventive film, a rust preventive film is formed by combining with phosphoric acid in addition to the above metal ions, and if necessary, a cation, anion, or chelating agent is added. Even when added, it has further excellent rust prevention properties.

In the case of a colorless or colored rust preventive film, the present invention uses, for example, a treatment liquid not containing chromium containing tannic acid containing polyhydric phenol carboxylic acid on the first rust preventive film layer. Therefore, the second rust preventive film layer is formed, so that the rust preventive property is more excellent.

The present invention also has a further rust prevention effect by overcoating the final treatment solution containing silicon at room temperature for a short time of about several seconds.

Since the present invention has almost the same process and reaction conditions as the formation of a rust preventive film by the current chromate method or trivalent chromium treatment liquid method in a galvanizing factory, the galvanizing and rust preventing processing factory Can be used without major modifications.

Furthermore, in the present invention, it can be seen that a cyan bath, a zincate bath, and a chloride bath, which are the main bath types of galvanization, have a very effective antirust effect, and the galvanizing apparatus is used as it is. It is also possible.

In addition to the production of chromium-free rust-proof coatings, the present invention provides additional anti-corrosion when it is necessary to further improve the corrosion resistance of rust-proof coatings in the current chromate method and trivalent chromium treatment solution method. It can be applied to needs such as changing the characteristics of the rust film without making major changes to the current process.

In the present invention, after activation by dilute nitric acid according to the plating situation after galvanization, rust prevention treatment may be performed in the same process.

Since the present invention does not contain chromium at all, it is not necessary to use a chromium reducing agent at the time of wastewater treatment, the wastewater treatment process can be simplified, and the economy is excellent.

Under the above-mentioned problems to be solved, the present inventors have conducted various experiments to solve these problems, and as a result of intensive studies, when producing a colorless or colored anticorrosive film with excellent corrosion resistance, As for the first rust preventive film, Al, Ti, V, Mn, Ni, Cu, Co, Mo, W, and metal ions that are considered to have good bondability with the plated zinc or zinc alloy and are also economical. Zr was selected. In addition, phosphate ions and the like, which are considered to provide an anticorrosive film with excellent adhesion, effective against the plated zinc or zinc alloy and the above metal ions, were selected. As the second rust preventive film, tannic acid containing phenol carboxylic acid was selected. For the final finishing solution, silicate ions that can be expected to be economical and effective were selected.

When producing a colorless or colored first anticorrosive film, the pH of the treatment liquid (referred to as a metal activation liquid) that forms a metal film simultaneously with activation is 0.5 to It is preferably in the range of 5.0, more preferably adjusted to pH 1.0 to 3.0. When the pH is less than 0.5, the plated zinc metal is remarkably eluted, and conversely, the corrosion resistance is lowered, and when the pH exceeds 5.0, the original activation cannot be performed.

In the case of producing a colorless or colored first rust preventive film, the content of metal ions in the metal activation liquid is not particularly limited, but the metal ion concentration is preferably 20 to 300 mmol / L, more preferably 30. ~ 200 mmol / L. If it is less than 20 mmol / L, the antirust effect cannot be expected, and if it exceeds 300 mmol / L, it is uneconomical.

When producing a colorless or colored first rust preventive film, the concentration of phosphate ions in the metal activation liquid is preferably 20 to 200 mmol / L, more preferably 30 to 100 mmol / L. If it is less than 20 mmol / L, sufficient rust preventive effect cannot be obtained, and if it exceeds 200 mmol / L, a thin film is applied on the surface of the galvanized metal, which hinders the formation of the second rust preventive film.

In the case of producing a colorless or colored first rust preventive film, pH adjustment in the metal activation liquid can include hydrochloric acid, sulfuric acid, nitric acid, acetic acid and the like as acids.

When the colorless or colored first rust preventive film is generated, the treatment temperature in the metal activation liquid is preferably about 10 ° C to 40 ° C. More preferably, it is 15 degreeC-35 degreeC. If the temperature is lower than 10 ° C, the reaction rate is slow and a sufficient rust-proof coating cannot be formed. The treatment time is preferably 3 to 20 seconds. More preferably, it is 5 to 15 seconds. If it is less than 3 seconds, the reaction is not sufficient, and if it exceeds 20 seconds, the zinc elution amount is large and the rust prevention effect is lowered.

When producing a colorless or colored first rust preventive film, the metal ions used in the metal activation liquid are not particularly limited, but are Al, Ti, V, Mn, Ni, Cu, Co, Mo, W, Zr. One type or a mixture of two or more types. The said compound is 1 type of the metal compound containing these metals, or a mixture of 2 or more types. As the metal compound, aluminum chloride, aluminum sulfate, aluminum acetate, ammonium aluminum sulfate and the like can be used as the Al compound. Titanium chloride or the like can be used as the Ti compound. As the V compound, ammonium vanadate, sodium vanadate, vanadium sulfate and the like can be used. As the Mn compound, manganese sulfate (II), manganese chloride (II), manganese nitrate (II), manganese acetate (II) and the like can be used. As the Ni compound, nickel sulfate, nickel chloride, nickel nitrate, nickel acetate and the like can be used. As the Cu compound, copper chloride, copper sulfate, copper nitrate, copper acetate and the like can be used. As the Co compound, cobalt chloride, cobalt nitrate, cobalt sulfate and the like can be used. As the Mo compound, ammonium molybdate, sodium molybdate and the like can be used. As the W compound, ammonium tungstate, sodium tungstate and the like can be used. As the Zr compound, zirconium chloride, zirconium sulfate, zirconium acetate or the like can be used.

In the case of producing a colorless or colored finish anticorrosive film, the silicon concentration in the final finishing solution is preferably 10 to 500 mmol / L, more preferably 15 to 200 mmol / L. If it is less than 10 mmol / L, there is no improvement in corrosion resistance, and if it exceeds 500 mmol / L, the economy is poor.

In the case of producing a colorless or colored finish anticorrosive film, the treatment time with the final finishing solution is not particularly limited, but is preferably 3 to 20 seconds, more preferably 5 to 10 seconds. If it is 3 seconds or less, a sufficient film is not formed, and if it exceeds 20 seconds, the generated rust preventive film is eluted. About reaction temperature, 10-40 degreeC is preferable, More preferably, it is 20-30 degreeC. If it is less than 10 ° C., an expected sufficient film cannot be obtained, and if it exceeds 40 ° C., the generated rust preventive film is eluted.

In the case of producing a colorless or colored finish rust-proof film, a silicate such as potassium silicate, sodium silicate, or lithium silicate may be used as silicon in the final finishing solution. Colloidal silica may also be used. Furthermore, a silane coupling agent may be used. Examples of silane coupling agents include, but are not limited to, commercially available γ-methacryloxypropyltrimethoxysilane, vinylmethoxysilane, vinylethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltrimethylsilane. And ethoxysilane.

In the case of producing a colorless or colored finish rust preventive film, the pH of the final finishing solution is not particularly limited, but is preferably in the range of pH 5.0 to 14.0, more preferably pH 7.0 to 13. Adjust to 0.0. When the pH of the final finishing solution is less than 5.0 or more than 14.0, the produced rust preventive film is eluted.

In the case of producing a colorless or colored finish rust preventive film, an organic acid may be used to adjust the pH of the final finishing solution. Organic acids include oxalic acid, citric acid, tartaric acid and the like.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not restrict | limited at all by these experimental examples.

[Example 1]
A test piece was prepared by applying a galvanized plating film thickness of 6 to 14 μm in a chloride bath to a pan head machine screw (M6 × 25 mm) with a cross hole made of SWRCH (carbon steel wire for cold heading). The metal activation solution of the present invention (vanadium 100 mmol / L, phosphate ion 100 mmol / L, symbol V1) was immersed in a solution adjusted to pH 1.5 with nitric acid at 25 ° C. for 10 seconds, washed with water, and further tannin. It was immersed in an acid (reagent) solution 5 g / L at 25 ° C. for 30 seconds, washed with water, and then immersed in a final finishing solution (potassium silicate 200 mmol / L) for 5 seconds. Furthermore, it dried at 50-70 degreeC for 5 minute (s), and the test piece which carried out the antirust process was obtained. Table 1 shows the color tone and corrosion resistance.

The obtained rustproofing test piece was tested for rustproofing power using a salt spray tester (STP-90, manufactured by Suga Test Instruments Co., Ltd.) in accordance with JIS-2371. As an evaluation method, the corrosion resistance was judged by examining the time until the white rust exceeded 5% on the test piece.

[Examples 2 to 25]
Experiments using various concentrations of metal activation solution, tannic acid solution, and final finishing solution were performed on the same test pieces as in Example 1, and rust-proof test pieces were obtained by the same drying method. . As for the results, as examples, Table 1 shows the pattern of the metal activation solution, tannic acid solution and final finishing solution, and summarizes the color tone and corrosion resistance at the same time. In Examples 18 to 19, the results of carrying out the same corrosion resistance without using the final finishing solution are shown.

[Examples 26 to 27]
The same test piece shown in Example 1 was subjected to zinc plating with a plating film thickness of 6 to 14 μm in a zincate bath, and this test piece was used as a metal activation liquid (vanadium 100 mmol / L) of the present invention. , Phosphate ion 100 mm / L and V1) was immersed in a solution adjusted to pH 1.5 with nitric acid at 25 ° C. for 10 seconds, washed with water, and further tannic acid (reagent) solution 5 g / L at 25 ° C. It was immersed for 30 seconds, washed with water, and then immersed for 5 seconds in the final finishing solution (potassium silicate 200 mmol / L symbol K1). Furthermore, it dried at 50-70 degreeC for 5 minute (s), and the test piece which carried out the antirust process was obtained (Example 26). In the same experiment, a test piece was also obtained for the sample that was not subjected to the final finishing solution (Example 27). Table 1 shows the color tone and corrosion resistance.

[Example 28]
The same test piece shown in Example 1, which was subjected to galvanization with a plating film thickness of 6 to 14 μm in a cyan bath, was used as a test piece, and this test piece was used as a metal activation liquid of the present invention (vanadium 100 mmol / L). , Phosphate ion 100 mm / L and V1) was immersed in a solution adjusted to pH 1.5 with nitric acid at 25 ° C. for 10 seconds, washed with water, and further tannic acid (reagent) solution 5 g / L at 25 ° C. It was immersed for 30 seconds, washed with water, and then immersed in a final finishing solution (potassium silicate 200 mmol / L, symbol K1) for 5 seconds. Furthermore, it dried at 50-70 degreeC for 5 minute (s), and the test piece which carried out the antirust process was obtained. Table 1 shows the color tone and corrosion resistance.

(Comparative Example 1) The same test piece used in Example 1 was subjected to galvanization with a plating film thickness of 6 to 14 μm in a chloride bath, and this test piece was adjusted to pH 1.5. After washing with a nitric acid solution, the test piece dried for 5 minutes at 50 to 70 ° C. was subjected to a corrosion resistance test using the above-mentioned salt spray tester, and the results are shown in Table 2.

(Comparative Example 2) The same test piece used in Example 1 was subjected to galvanization with a plating film thickness of 6 to 14 μm in a chloride bath, and this test piece was adjusted to pH 1.5. After being activated by dipping in a nitric acid solution at 25 ° C. for 10 seconds, washed with water, further immersed in a tannic acid solution 5 g / L for 30 seconds at 25 ° C., washed with water, and then dried at 50 to 70 ° C. for 5 minutes. Were subjected to a corrosion resistance test using the above-mentioned salt spray tester, and the results are shown in Table 2.

(Comparative Examples 3 to 5) The same test piece used in Example 1 was subjected to galvanization with a plating film thickness of 6 to 14 μm in a chlorination bath, and this test piece was adjusted to pH 1.5. After activating by immersing in dilute nitric acid solution at 25 ° C. for 10 seconds, rinsing with water, further immersing in tannic acid solution 5 g / L for 30 seconds at 25 ° C., rinsing with water and then immersing in potassium silicate solution, The test piece dried for 5 minutes at 50 to 70 ° C. was subjected to a corrosion resistance test using the above-mentioned salt spray tester, and the results are shown in Table 2.

(Comparative Example 6) The same test piece as shown in Example 1 was subjected to galvanization with a plating film thickness of 6 to 14 µm in a chloride bath, and this test piece was used as a metal activation solution of the present invention. (Vanadium 100 mmol / L, phosphate ion 100 mm / L) was immersed in a solution adjusted to pH 1.5 with nitric acid at 25 ° C. for 10 seconds, washed with water, dried at 50 to 70 ° C. for 5 minutes, and rust-proof. A treated specimen was obtained. Table 2 shows the color tone and corrosion resistance.

The same can be said from Examples 1-28 and Comparative Examples 1-6.
{Circle around (1)} In all of the examples, the corrosion resistance of the results of the treatment with the metal activating solution is drastically improved in all cases.
(2) Regarding the metal ion concentration in the metal activation solution, no significant difference was observed between 50 mmol / L and 100 mmol / L.
(3) Vanadium, molybdenum and nickel showed good results as metals.
(4) When Examples 1 and 9 were compared with Examples 18 and 19, it was found that the final finishing agent also contributed to the improvement of corrosion resistance.
(5) Regarding the difference in plating bath, in this experiment, the results of corrosion resistance were obtained in the order of chloride bath> zincate bath> cyan bath.
(6) When producing a colorless or colored antirust chemical conversion film, from the examples and comparative examples, the metal activation solution alone (Comparative Example 6) and the tannic acid treatment alone (Comparative Example 2) When the metal activation treatment, the tannic acid treatment and the final finishing treatment were performed, the corrosion resistance was dramatically improved.

The invention's effect

In the process of forming a rust preventive film on the surface of zinc or zinc alloy-plated metal, chromium-free metal ions and phosphate ions that can become the first layer of rust preventive film simultaneously with the activity during nitric acid activation as the first step In the past, a single layer of rust preventive film could not provide a sufficient rust preventive effect by simultaneously generating a rust preventive film mainly composed of a rust-free film and then forming a chrome-free second layer or more. The rust prevention ability is dramatically improved by the generation of a multi-layered rust prevention film, which has a good appearance in various colors, and can be incorporated into conventional equipment processes. It is possible to provide a chromium-free rust preventive treatment liquid and a rust preventive film treatment method that suppresses the above.

It is process drawing of the surface treatment method concerning this invention.

Claims (8)

During the nitric acid activation step, which is the first step, in the production of a colorless or colored rust-preventive coating after zinc or zinc alloy plating, the first rust-preventive coating layer mainly composed of metal ions is activated at the same time as activation. Forming a second anticorrosive film layer at the second step of the anticorrosive film forming step, forming a highly corrosion-resistant anticorrosive film, and further providing a final finish film as necessary. A chromium-free rust-proof coating treatment method. In the treatment in the first step, a treatment liquid containing 20 to 300 mmol / L of metal ions and 20 to 200 mmol / L of phosphate ions is selected from acids such as nitric acid, sulfuric acid, phosphoric acid, and acetic acid. Or the chromium-free process liquid which forms a metal rust preventive film simultaneously with the activation adjusted to pH 0.5-5.0 with two or more types of acids. Simultaneously with the activation, the metal ion according to claim 1 is one kind or a mixture of two or more kinds of metal ions of Al, Ti, V, Mn, Ni, Cu, Co, Mo, W, and Zr. A chrome-free treatment solution that forms a metal film. A chromium-free treatment liquid for forming a metal film, characterized in that the treatment liquid according to claim 2 contains a cation or anion different from the metal ions contained in the treatment liquid and an organic compound chelating with the metal ions. . The processing method according to claim 2, wherein a chromium-free rust preventive film such as an inorganic film, an organic film, or an organic-inorganic composite film is formed in the second step on the metal rust preventive film generated simultaneously with activation. A final finishing solution containing 10 to 500 mmol / L of silicon as a finishing solution. As the silicon of the finishing treatment liquid, a chromium-free final finishing treatment liquid of one or more kinds in a coupling agent containing sodium silicate, potassium silicate, silicate such as lithium silicate, and silicon. 5 to 200 mmol / L of one or more organic acids are further added to the finishing solution.

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