JPH0686667B2 - Metal surface treatment method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for coating iron or an iron alloy with a high corrosion resistance and a high adhesion coating. More specifically, the present invention relates to a method for anticorrosion treatment of a metal surface, which comprises forming a zinc or zinc alloy coating on the surface of iron or an iron alloy, then performing a non-aqueous chromate treatment, and then applying an organic or inorganic coating to form a coating.

BACKGROUND OF THE INVENTION In order to improve the adhesion of paint when painting metal,
It is well known that a phosphate treatment is applied as a base treatment, or electrogalvanizing, hot dip galvanizing, or chrome rinsing is applied to improve corrosion resistance. Phosphate treatment improves the adhesion of paints, but has little effect on corrosion resistance. Galvanizing improves the corrosion resistance but reduces the adhesion of paint. It is also possible to apply a chrome rinse on the phosphate treatment to improve the corrosion resistance, but since this is generally performed in the form of an aqueous solution,
There is a problem of environmental pollution due to drainage. Further, there is a method of coating powder coating material by a fluidized dipping method or a so-called resin coating method in which an object to be treated is heated in advance. In this case, in the case where the surface treatment such as the phosphate treatment or the zinc plating is performed, the treatment film is attacked by preheating, the adhesion of the coating film is remarkably lowered, and the corrosion resistance of the comprehensive film is extremely deteriorated. Despite the strong desires of those skilled in the art, there has been no suitable surface treatment for improving these disadvantages.

Relatively recently, the present applicants developed a technology for a zinc coating by a special blast and a non-aqueous chromate treatment suitable for it, and conducted earnest research on the relationship between the coating by these developed technologies and various coatings. It has been found to have a very good compatibility with.

That is, iron or an iron alloy is used as a core, and particles formed by coating zinc or a zinc alloy around the core are projected onto a metal member to form a zinc coating film on the surface, and a non-aqueous system is formed on this film. It is a method of applying an organic or inorganic coating after the chromate treatment. According to this method, the zinc coating film formed by the projection of zinc or zinc alloy-coated iron or iron alloy particles is firmly adhered to the metal member and becomes a film having voids, and at the same time, the corrosion resistance to the metal member is reduced. Show minutes. Furthermore, by applying a non-aqueous chromate treatment to the formed film, extremely high anticorrosive properties are exhibited. The composite coating formed in this way has very good compatibility with various paints due to its morphology and properties,
The paint adhesion and the overall coating corrosion resistance are excellent. Further, since the composite coating has extremely good heat resistance, it is extremely effective for paints that are baked at high temperatures and thermoplastic fluid immersion paints that are preheated to high temperatures before coating. The inventors of the present invention have found that, by combining these different techniques, unexpectedly high performance can be obtained as a base treatment for various coating systems, and thereby various problems of the above-mentioned conventional techniques can be solved, and the present invention is completed. Came to.

Structure of the Invention That is, according to the present invention, iron or iron alloy as a core, from the aggregate of independent multi-layer particles formed by depositing zinc or zinc alloy through the iron-zinc alloy layer around the core A zinc coating film is formed on the surface of the iron or iron alloy by blasting the blast material onto the surface of the iron or iron alloy (hereinafter referred to as the blast zinc coating method), and a non-aqueous chromate treatment is applied to the surface thus formed. After applying, an organic paint (however, excluding the dispersion liquid of polytetrafluoroethylene having an organic resin binder as a disperse phase) is applied to the surface of the core to form a coating film. A surface treatment method is provided.

As used herein, the term iron alloy means a material consisting essentially of iron and also includes stainless steel.

According to the method of the present invention, while maintaining the advantages of the blast zinc coating method, the corrosion resistance performance is dramatically improved by the non-aqueous chromate treatment, the adhesion to the paint is extremely good, and the coating base has good corrosion resistance and can be used for any purpose. A coating system that meets the requirements can be obtained.

DETAILED DESCRIPTION OF THE INVENTION The first process of the present invention, namely the blast zinc coating method, uses iron or an iron-zinc alloy as a core, and deposits zinc or a zinc alloy around the core through an iron-zinc alloy layer. Is a process of projecting a blast material composed of an aggregate of independent multi-layered particles as described above to form a zinc or zinc alloy coating. The blast material used in this blast zinc coating method is such that the weight ratio of iron and zinc in the aggregate is in the range of iron 10 to 95% and zinc 5 to 90%, and iron powder is added to molten zinc. It is manufactured by a method or a method of heat-treating a mixture of zinc powder and iron powder. The size of the blast material is about to pass through a 16-mesh screen, and this is projected onto the surface of the object to be processed using a blast machine. The blast zinc coating method is described in more detail in JP-A-56-45372.

The second treatment of the present invention, that is, the non-aqueous chromate treatment, contains a chromic acid compound, an organic solvent (mainly a halogenated hydrocarbon solvent) and alcohols as a solubilizing agent as main components, and if desired, a stabilizer or a stabilizer. A composition containing a reaction accelerator forms a chromate film.
-5288 (DuPont), Japanese Patent Publication No. 42-3363 (DuPont), Japanese Patent Application Laid-Open No. 56-62970 (Soda Tokuyama), Japanese Patent Application Laid-Open No. 55-97476 (Nippon Paint), Japanese Patent Application Laid-Open No. 56-139679 (Nippon Paint), Japanese Patent Application Sho 59-15
3028 (Japan Dakuro Shamrock) and the like.

The organic solvent used in the non-aqueous chromate treatment of the present invention is a halogenated hydrocarbon having 1 to 2 carbon atoms and containing chlorine and / or fluorine, such as methylene chloride, trichloroethane, trichloroethylene, perchloroethylene,
Trichlorotrifluoroethane, dichlorotetrafluoroethane, tetrachlorodifluoroethane and mixtures thereof can be preferably used.

The chromic acid compound used in the method of the present invention is called chromic anhydride or chromium trioxide, and the compound corresponding to the chemical formula CrO ₃ is most preferable. The chromic anhydride is used in a concentration of 0.01 to 10 parts, preferably 0.1 to 5 parts, relative to 100 parts by weight of the halogenated hydrocarbon solvent (hereinafter simply referred to as "parts"). When the amount of chromic anhydride is less than 0.01 part, the rate of chromate reaction becomes slow, and when it is more than 10 parts, decomposition of the halogenated hydrocarbon solvent or solubilizer in the bath becomes remarkable,
A normal film is not formed, and corrosion resistance tends to decrease.

The solubilizer used in the process of the present invention is a secondary or tertiary alcohol soluble in the halogenated hydrocarbon solvent and having 3 to 20 carbon atoms. Generally, secondary propanol, tertiary butanol, tertiary amyl alcohol, triphenylcarbinol and the like are preferably used, but the components of the treatment liquid of the present invention are uniformly dissolved and stable even for long-term use. Therefore, tertiary butanol and tertiary amyl alcohol are particularly preferable. The solubilizing agent is necessary in an amount of at least 1 part or more with respect to 100 parts of the halogenated hydrocarbon solvent, and may be 20 parts or more. The larger the amount of the solubilizer, the more the amount of chromic anhydride dissolved. If the amount of the solubilizing agent is less than 1 part, the solubilizing power will be insufficient and it will be difficult to uniformly dissolve the components, and it is possible to use 20 parts or more, but it may be flammable depending on the use conditions. In some cases, it is preferable to set that point as the upper limit.

The stabilizers used in the method of the present invention are amines, quinones, nitro, azo or azoxy aromatic compounds, thioureas, dienes, organic nitrites, zinc fluoride, zinc oxide, and many other known compounds. In the case of a chlorinated fluorinated hydrocarbon solvent, no stabilizer may be used, which is advantageous in this respect. Examples of these compounds include N-nitrodiphenylamine, azoxybenzene, hydroquinone, diisobutylamine, pentadiene, amyl nitrite, and many other compounds. These may be used alone or in combination of two or more, and the amount thereof is preferably 0.001 to 5 parts with respect to 100 parts of the halogenated hydrocarbon solvent. Use of amounts outside this range results in little benefit or is beyond the efficacy limits and is wasted.

The reaction accelerator used in the method of the present invention is hydrogen fluoride, an organic acid, water or the like.
They may be used as a mixture of two or more kinds, or may not be used at all depending on the situation. The organic acid may be an organic acid having 1 to 20 carbon atoms and can be dissolved in the mixture of the above components. Examples of these include formic acid, acetic acid, lactic acid, oxalic acid, fumaric acid, maleic acid, malic acid and the like. These reaction accelerators are used in an amount of 0.001 part or more with respect to 100 parts of the halogenated hydrocarbon solvent, and in the case of hydrogen fluoride and an organic acid, preferably used in an amount of 0.12 parts or more,
In the case of water, it is preferable to use it within the range in which a system in which it is uniformly dissolved can be maintained. If the amount is less than these ranges, the effect cannot be expected, and if the amount exceeds the range, defects such that the corrosive action on the object to be treated or the device becomes remarkable or the uniform system cannot be maintained occur.

The chromate treatment liquid used in the method of the present invention is substantially non-aqueous, the halogenated hydrocarbon solvent fulfills the task of degreasing and washing, makes the treatment liquid nonflammable, and the solubilizer uniformly dissolves all components. It is necessary that all components are uniformly dissolved in the treatment liquid. If it is not uniform, a coating film is formed unevenly and corrosion resistance is reduced.

Regarding the first and second treatments of the method of the present invention, that is, the combination of the blast zinc coating method and the non-aqueous chromate treatment method, the applicant of the present application filed a patent application (Japanese Patent Application No. 59-1).
88784).

As the third treatment of the present invention, that is, a method of applying an organic or inorganic coating to an object to be treated, various coating methods which are generally used are used.

As the pretreatment for coating, it is sufficient to apply the blast zinc coating method and the non-aqueous chromate treatment method described above, and the coating can be performed as it is, unless it is contaminated.

The paint used is a solvent-based paint, except for the polytetrafluoroethylene dispersion containing the organic resin binder as the dispersed phase.
Any type of paint such as water-soluble paint or powder paint may be used. As the coating method, any method currently used by those skilled in the art such as dipping, brush coating, electrostatic spraying, air spraying, electrodeposition, fluidized dipping, and flow coating can be used.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be illustrated in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

The test piece, using 70 × 150 × 2mm cold rolled steel sheet, after degreasing by steam cleaning of trichloroethane, blast zinc coating treatment by projection of the zinc or zinc alloy adhered blast material for 30 minutes, the test piece surface 100 To 120 mg / dm ² to form a zinc coating film, which is then subjected to non-aqueous chromate treatment to form a chromate film on the surface of the test piece, and various coatings are applied to the obtained test piece to perform a performance test. I went to Details of the performance test method are as described below.

(1) Cross-cut adhesion test (primary adhesion test) In accordance with the cross-cut test of the general paint test method (JIS K 5400). About the sample after 24 hours of coating After making a grid-like cut so that 100 pieces of 1 mm square are formed on the coating film with a cutter knife, stick the cellophane tape (18 mm width) strongly and stick it, 45 degree Peel strongly by pulling at an angle and evaluate the adhesiveness by the number of remaining grids.

(2) Salt spray test This is based on the JIS Z 2371 salt spray test method. 5% saline solution at 35 ℃
Continuous spray with. The coating film of the test piece is preliminarily filled with a scratch (cross cut) reaching the iron substrate with a cutter knife.
After the test, evaluate the occurrence of blisters, peeling, red rust, and blisters around the crosscut on the flat surface without any scratches.

(3) Secondary adhesion test After completion of the corrosion resistance test, a cellophane tape adhesion test is performed after putting a grid on the flat surface, or a cellophane tape adhesion test is performed on the cross cut part. Those with less peeling of the coating film are evaluated as having good corrosion resistance.

Example 1 In preparation of the test piece, following the blast zinc coating treatment,
Dip for 1 minute at reflux temperature in a treatment solution containing 15 parts t-butanol, 2 parts chromic anhydride, and 0.01 parts oxalic acid uniformly dissolved in 100 parts trichlorotrifluoroethane for steam cleaning. After that, it was taken out and cooled to room temperature for non-aqueous chromate treatment, and the obtained test pieces were coated with various paints to a film thickness of 20 μm and subjected to a performance test. The paint, coating conditions and test results are shown in Table 1.

Comparative Example 1 As a typical example of the conventional coating base treatment, various coatings were performed using the most commonly used zinc phosphate treatment, and Comparative Example 1 is shown in Table-1.

Example 2 A sample was prepared in the same manner as in Example 1 except that the composition of the non-aqueous chromate treatment liquid shown in Table 2 was used, and the results shown in Table 1 were obtained.

Example 3 In Example 1, the anion-type electrodeposition coating material and the cation-type electrodeposition coating material were used to apply a film having a thickness of 20 μm and the performance test was performed. The test results are shown in Table 3.

Comparative Example 2 In Example 3, as a representative example of the conventional coating base, instead of the coating base treatment according to the present invention, the most commonly used zinc phosphate treatment was used for electrodeposition coating, and the performance test was performed. I served. The test results are shown in Table 3.

Example 4 In Example 1, electrostatic coating was performed using the epoxy resin powder coating material, and baking was performed at 200 ° C. for 20 minutes to obtain a film thickness of 50 μm. This sample was subjected to a performance test, and the results shown in Table 4 were obtained.

Comparative Example 3 In Example 4, coating was performed using a sample that had been treated with zinc phosphate instead of the coating base according to the present invention, and the performance test results in Table 4 were obtained.

Example 5 In Example 1, the polyvinyl chloride resin powder coating material was used for coating by a fluidized-bed method. For preheating before dipping in the paint flow tank, test specimens in a preheating furnace set at 350 to 400 ° C.
The coating was carried out by heating to 280 ° C., immediately after which it was completely immersed in the fluidized bed for a few seconds and then pulled up. Post-heating was performed in a heating furnace set at 230 to 240 ° C. The film thickness is about 0.
It was 3 mm. This sample was subjected to a performance test, and the results shown in Table 4 were obtained.

Comparative Example 4 In Example 5, the same coating was carried out using a sample material (iron base material) which had been subjected to rust removal by pickling and degreasing with trichlorethylene instead of the coating base according to the present invention, and this sample was subjected to a performance test. The results shown in Table 4 were obtained.

Comparative Example 5 In Comparative Example 4, the same coating was carried out using a test piece treated with zinc phosphate instead of the sample material (iron substrate), and this sample was subjected to a performance test to obtain the results shown in Table-4. It was

Comparative Example 6 In Comparative Example 4, the same coating was carried out using a test piece that had been subjected to electrogalvanizing yellow chromate treatment instead of the sample material (iron base material), and this sample was subjected to a performance test.
Got the result.

Claims (1)

[Claims] 1. A blast material comprising iron or an iron alloy as a core, and an aggregate of independent multi-layer particles formed by depositing zinc or a zinc alloy around the core with an iron-zinc alloy layer interposed between the iron and the blast material. A zinc coating film is formed on the surface of the iron or iron alloy by projecting it onto the surface of the iron alloy, and the surface of the surface thus formed is subjected to a non-aqueous chromate treatment. A surface treatment method of iron or an iron alloy, which comprises applying a dispersion of polytetrafluoroethylene having a binder as a dispersed phase to form a film.