JP2950481B2 - Metal surface treatment method - Google Patents

Abstract

A method for the corrosion-prevention treatment of a metal suface comprises projecting onto a metal surface a shot-blast particulate material consisting of a core of iron or an iron alloy, an undercoat of a iron-zinc alloy and a top coat of zinc or a zinc alloy, thereby forming a coating film of zinc or the zinc alloy on the metal surface, and bringing the thus coated metal surface into contact with an aqueous suspension of silica and an aqueous solution containing ions of at least one metal selected among Ti, Zr, Mg, Ba, Sr, W, Ni, Co, Sn, Mo, and Mn.

Description

Description: TECHNICAL FIELD The present invention relates to an anticorrosion treatment for a metal surface.

(Prior art and its problems) As a conventional anticorrosion treatment of a metal surface, a method of subjecting zinc to hot dip plating or electroplating and then chromate treatment is well known. A blast galvanizing method is also known. Recently, an improved blast material consisting of an aggregate of independent particles composed of iron or iron alloy particles as a nucleus and a zinc or zinc alloy layer adhered around the iron or zinc alloy layer through an iron or zinc alloy layer has been developed. An improved blast zinc coating method comprising projecting onto an alloy surface was developed (JP-B-59-9312). This method is referred to herein as the improved blast zinc coating method.

This method is a revolutionary method with low cost equipment, low energy consumption and low environmental pollution factors, but the zinc coating formed by this method is still not enough in corrosion resistance, and the coating amount of 100 mg / dm ² In the salt spray test, red rust occurs within 24 hours. This is considered to be because the zinc coating formed by this method is an iron-zinc alloy.

On the other hand, from the viewpoint of metal surface treatment, it is the actual situation that sufficient corrosion resistance cannot be obtained only by treatment by zinc plating, zinc alloy plating and the improved blast zinc coating method. Therefore, when the object to be treated is used for corrosion resistance, it is necessary to perform a post-treatment.

A relatively simple method for that is chromate treatment. When an appropriate chromate treatment is performed after the treatment by the improved blast zinc coating method, neither white rust nor red rust is generated even for 240 to 1000 hours or more (Japanese Patent Application Laid-Open Nos.
−19477). Therefore, when the improved blast zinc coating method is applied to metals for corrosion resistance use, it is considered that it is essential to perform chromate treatment as a post-treatment.

However, the chromate treatment, which is a post treatment, contains a hexavalent chromium compound in the solution. Hexavalent chromium compounds are harmful to health and safety and pollution problems. Therefore, when a hexavalent chromium compound is used industrially, it is necessary to pay close attention to its handling.

However, although various methods have been studied as post-treatment methods having excellent corrosion resistance, they could not be developed beyond the chromate treatment.

(Means for Solving the Problems) As a result of intensive studies on a post-treatment method of a treated product by the improved blast zinc coating method, the present inventors have developed a post-treatment which is not inferior to the chromate treatment in terms of corrosion resistance. That is, after the improved blast zinc coating method is applied to the metal material, the silica suspension and at least one ion of Ti, Zr, Mg, Ba, Sr, W, Ni, Co, Sn, Mo, and Mn are included. It has been found that by treating with an aqueous solution, a result comparable to that of the chromate treatment can be obtained.

[Configuration of the invention]

The present invention relates to a method of projecting a blast material comprising an aggregate of multi-layer coated particles comprising iron or an iron alloy as a nucleus and surrounding the nucleus with a zinc or zinc alloy through an iron-zinc alloy layer, and projecting the blast material onto a metal surface. Alternatively, a coating film of a zinc alloy is formed; the surface thus formed is treated with an aqueous silica suspension and T
Provided is a metal surface treatment method comprising contacting with an aqueous solution containing at least one metal ion of i, Zr, Mg, Ba, Sr, W, Ni, Co, Sn, Mo, and Mn.

The pre-treatment of the method of the present invention is basically the same as that described in JP-B-59-93.
No. 12 and its known improvements.

The silica used in the method of the present invention may be a precipitated silica or a gas-phase hydrolyzed silica, that is, anything that forms an aqueous suspension. Silica is contained in an amount of 0.1 to 20 parts by weight based on 100 parts by weight of water. When the amount is less than 0.1 parts by weight, a film exhibiting sufficient corrosion resistance is not formed on the surface of the processed material, and when the amount is more than 20 parts by weight, a thick gel-like film is formed on the surface of the processed material, which is not practical.

When the silica suspension is treated alone, the temperature of the treatment solution is optimally in the range of 5 to 40C. If the temperature is lower than 5 ° C., drying after the treatment takes a long time, which is not practical. If the temperature is higher than 40 ° C., SiO ₂ in the processing solution gels at an early stage.

The immersion time is optimally in the range of 10 to 250 seconds. 1
If the time is less than 0 seconds, a complete film is not formed on
Times longer than seconds are not practical lengths when considering processing processes.

Treatment liquids are Ti, Zr, Mg, Ba, Sr, W, Ni, Co, Sn, M
It is an aqueous solution containing one or more kinds of o and Mn ions.

The metal ion source may be any water-soluble salt of a metal.
The pH of the solution does not matter. It may be simply an aqueous solution.

The concentration of each ion is 0.01 to 20 parts by weight per 100 parts by weight of water. If the amount is less than 0.01 part by weight, the progress of the reaction is slow and the treatment time becomes long. If the amount exceeds 20 parts by weight, sludge-like products adhere to the surface of the processed material after the treatment.

The temperature of the treatment liquid is optimally in the range of 5 ° C. to the boiling point. 5
If the temperature is lower than ° C, drying after the treatment takes a long time, which is not practical.

The immersion time is optimally in the range of 3 to 250 seconds.
Immersion for less than 3 seconds or more than 250 seconds is not practical in the treatment process.

An object to be treated is treated in each liquid by the improved blast zinc coating method.

When performing these two treatments simultaneously in the same medium, the temperature of the treatment liquid is in the range of 5 ° C to 40 ° C. If the temperature is lower than 5 ° C., it takes a long time to dry after the treatment, which is not practical. If it exceeds 40 ° C., silica gels at an early stage.

The immersion time is suitably in the range of 10 to 250 seconds. If it is less than 10 seconds, a complete film is not formed on the surface of the processed material, and if it exceeds 250 seconds, it is not practical as a processing process.

The contact treatment is carried out by dipping, coating, spraying, etc., but dipping is most practical.

The wet surface treatment in combination with the improved blast zinc coating according to the method of the present invention has an effect comparable to that of chromate treatment,
Low pollution problem like chromate treatment.

It is presumed that the effect of the present invention is that silica is absorbed in the zinc-coated phase by filling its pores, and metal ions combine with the silica to form an amorphous film.

(Specific Disclosure of the Invention) Hereinafter, the present invention will be specifically disclosed by Examples and Comparative Examples. The present invention is not limited by these examples.

A 100 × 50 × 2.0 mm mild steel test panel was used for the test. After the test panel was degreased by steam with trichloroethane, it was treated by a modified blast zinc coating method described in JP-B-59-931 to form a zinc-iron alloy coating on the surface. This test panel was subjected to post-processing of the example and the comparative example. Test panel corrosion resistance test
A salt spray test specified in JIS-Z23711 was performed, and the occurrence of rust was examined over time.

As the electrogalvanized panel, a 100 × 50 × 2.0 mm mild steel test panel plated with electrogalvanized steel having a plating thickness of 8 μm was used for the test.

In the following examples, “parts” simply means “parts by weight”.

Example 1 To 100 parts of deionized water, 0.5 part of silica was added, and the mixture was uniformly stirred. A test panel treated by the improved blast zinc coating method was immersed in this treatment solution for 30 seconds, and then dried with warm air. did. Next, for 100 parts of deionized water, K ₂ ZrF ₆ was added to Zr
0.5 parts as ions were added, and the mixture was stirred uniformly, and the object was immersed at room temperature for 60 seconds. Thereafter, it was dried with warm air. This sample was subjected to a corrosion resistance test. Table 1 shows the results.

Example 2 The silica suspension of Example 1 was applied using a brush, and then dried with warm air. Next, the K ₂ ZrF ₆ -containing liquid of Example 1 was applied using a brush, and then dried with hot air. This sample was subjected to a corrosion resistance test. Table 1 shows the results.

Example 3 To 100 parts of deionized water, 5 parts of silica was added, and N was added.
Add 1 part of i (SO ₃ ) ₂ · 4H ₂ O as Ni ions, stir uniformly, immerse the test panel treated by the improved blast zinc coating method in this treatment solution for 60 seconds, then dry with hot air did. This sample was subjected to a corrosion resistance test. Table 1 shows the results
Shown in

Example 4 The solution containing silica and Ni (SO ₃ ) ₂ .4H ₂ O of Example 3 was applied using a brush, and then dried with warm air. This sample was subjected to a corrosion resistance test. Table 1 shows the results.

Example 5 To 100 parts of deionized water, 10 parts of silica was added, and M
One part of nCl ₂ .4H ₂ O was added as Mn ions, and the mixture was uniformly stirred. The test panel treated by the improved blast zinc coating method was immersed in the treatment solution for 60 seconds, and then dried with hot air.
This sample was subjected to a corrosion resistance test. Table 1 shows the results.

Example 6 The solution of SiO ₂ and MnCl ₂ .4H ₂ O of Example 5 was applied by spraying, and then dried with hot air. This sample was subjected to a corrosion resistance test. Table 1 shows the results.

Example 7 5 parts of silica was added to 100 parts of deionized water, uniformly stirred, and a test panel treated by the improved blast zinc coating method was immersed in the treatment solution for 30 seconds, followed by hot air drying. did. Next, for 100 parts of deionized water, K ₂ ZrF ₆
As r ion, 0.5 parts of, in addition 5 parts of CoSO ₄ · 8H ₂ O as Co ion concentration, uniformly stirred, and the said object to be treated was dipped for 60 seconds at normal temperature bath. Thereafter, it was dried with warm air. This sample was subjected to a corrosion resistance test. Table 1 shows the results.

Example 8 The silica suspension of Example 7 was applied using a brush, and then dried with warm air. Next, K ₂ ZrF ₆ and CoSO _{4 of} Example 7 were used.
・ After applying the 8H ₂ O-containing solution using a brush, it was dried with hot air. This sample was subjected to a corrosion resistance test. Table 1 shows the results.

Example 9 15 parts of silica was added to 100 parts of deionized water, uniformly stirred, and a test panel treated by the improved blast zinc coating method was immersed in this treatment solution for 30 seconds, followed by hot-air drying. Next, K ₂ TiF ₆ was added to 100 parts of deionized water with Ti ions as 0.5 parts.
Was added and stirred uniformly. This sample was subjected to a corrosion resistance test. Table 1 shows the results.

Example 10 15 parts of silica was added to 100 parts of deionized water, uniformly stirred, and a test panel treated by the improved blast zinc coating method was immersed in this treatment solution for 10 seconds, followed by hot-air drying. Next, in 100 parts of deionized water, MgSO ₄ .7H ₂ Oi as Mg
0.5 parts, (NH ₄ ) 6 Mo ₇ O ₂₄ as Mo 0.5 parts, and SrCl ₂
Add 0.7 part of 6H ₂ O as Sr ion, stir evenly,
The object was immersed at room temperature for 60 seconds. This sample was subjected to a corrosion resistance test. Table 1 shows the results.

Example 11 20 parts of silica was added to 100 parts of deionized water, uniformly stirred, and a test panel treated by the improved blast zinc coating method was immersed in the treatment solution for 30 seconds, followed by hot-air drying. Next, in 100 parts of deionized water, 0.5% of SnCl ₂ was used as Sn ions.
The parts and CoSO ₄ · 8H ₂ O was added 3 parts of a Co ion was homogeneously stirred. Immerse the object to be treated at room temperature for 60 seconds,
Thereafter, it was dried with warm air. This sample was subjected to a corrosion resistance test. Table 1 shows the results.

Comparative Example 1 1.0 part of chromic anhydride and 0.1 part of sulfuric acid were added to 100 parts of deionized water.
And 0.1 part of nitric acid were uniformly dissolved to prepare a treatment solution. A test panel treated by the modified blast zinc coating method was immersed for 4 seconds in this. After immersion, leave in the air and wash with water,
Hot air dried. This sample was subjected to a corrosion resistance test. Table 1 shows the results.

Comparative Example 2 2.0 parts of chromic anhydride, chromium nitrate in 100 parts of deionized water
A treatment solution in which 0.1 part was uniformly dissolved was prepared. A test panel treated by the modified blast zinc coating method was immersed for 4 seconds in this. After immersion, it was left in the air, washed with water, and dried with warm air. This sample was subjected to a corrosion resistance test. Table 1 shows the results
Shown in

Comparative Example 3 A treatment liquid was prepared by uniformly dissolving 15 parts of t-butanol, 2 parts of chromic anhydride, and 0.01 part of oxalic acid with respect to 100 parts of trichlorotrifluoroethane. This was boiled in a tank having an aggregating device at the top, and the aggregating liquid at the top was refluxed into the tank.

A test panel treated by the modified blast zinc coating method was immersed in this for 60 seconds. After immersion, it was forcibly dried in fresh air at 40 ° C. for 3 minutes, further washed in a solution composed of trichlorotrifluoroethane and t-butanol, and then dried. This sample was subjected to a corrosion resistance test. Table 1 shows the results.

Comparative Example 4 A treatment liquid was prepared by uniformly dissolving 1 part of tannic acid in 100 parts of deionized water. A test panel treated by the modified blast zinc coating method was immersed in a treatment solution bath at 70 ° C. for 4 seconds. After immersion, it was left in the air, washed with water, and dried with warm air. This sample was subjected to a corrosion resistance test. Table 1 shows the results.

Comparative Example 5 A test panel treated by the improved blast zinc coating method was subjected to a corrosion resistance test without any chemical conversion treatment. Table 1 shows the results.

Comparative Example 6 Instead of the object to be treated by the improved blast zinc coating method,
The test panel subjected to electrogalvanization was treated using the treatment solution used in Example 1. This sample was subjected to a corrosion resistance test. Table 1 shows the results.

Claims (5)

(57) [Claims] A blast material comprising an aggregate of multi-layer coated particles comprising iron or iron alloy as a core and zinc or zinc alloy coated around the core via an iron-zinc alloy layer is projected onto a metal surface. Forming a coating of zinc or a zinc alloy;
The surface thus formed is treated with an aqueous silica suspension and
A metal surface treatment method comprising contacting with an aqueous solution containing at least one metal ion of Ti, Zr, Mg, Ba, Sr, W, Ni, Co, Sn, Mo, and Mn. 2. The method according to claim 1, wherein the treatment with the silica suspension and the treatment with the solution containing metal ions are performed in the same medium. 3. The method according to claim 1, wherein the treatment is carried out first with a silica suspension and then with a metal ion solution. 4. The method according to claim 1, wherein the concentration of silica in the silica suspension is 0.1 to 20 parts by weight per 100 parts by weight of water.
The method according to any of the above items. 5. The method according to claim 1, wherein the concentration of metal ions in the aqueous metal ion solution is 0.01 to 20 parts by weight per 100 parts by weight of each water.