JPS6046197B2 - Post-treatment method for phosphate film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for post-treatment of phosphate coatings, more specifically,
A post-treatment that makes it possible to improve the corrosion resistance of the phosphate film and, ultimately, the painted surface on the film by bringing the treated product on which a phosphate film has been formed into contact with a zinc phosphate treatment solution and energizing it. Regarding the method.

Conventionally, as a pre-treatment for metals to be painted or as a temporary anti-corrosion treatment without painting, the method of first applying a phosphate coating to the metal and then cleaning with a dilute chromic acid aqueous solution is as follows:
It is known to be effective in preventing metal corrosion and the resulting deterioration of the appearance of painted surfaces.

However, such ROM-based post-treatment cleaning is accompanied by pollution problems due to the toxicity of the cleaning liquid, and the wastewater treatment is troublesome, so sufficient wastewater treatment equipment is required for practical use. In response to this, recently, chromium-free post-treatment cleaning methods for phosphate coatings have been developed as a countermeasure against pollution problems. A cleaning method (see Japanese Unexamined Patent Publication No. 49-104845) is known. However, the corrosion resistance provided by these methods is significantly different from that achieved by the above-mentioned chromium-based cleaning, and the required performance is currently not fully satisfied. On the other hand, as a treatment method for temporarily preventing rust on a metal surface and improving corrosion resistance after painting, the treated object is immersed in a zinc phosphate treatment solution and an alternating current is applied at 0.000000000000000000000000000,000,000,000,000 is applied as shown in Japanese Patent Publication No. 49-4622. 3-7
．． There is a method of coating chemical conversion treatment while dividing the current at a density of 0A/d Go, which can be expected to have sufficient corrosion resistance, but the current density is high and the processing time is long, so the amount of electricity used is large, so the running cost is high. was expensive and impractical.

Therefore, the present inventors eliminated these drawbacks and conducted extensive research into what factors affect corrosion resistance, including metals, chemical conversion coatings, and coating systems, and as a result, they solved the problem using the method shown below.

In other words, by contacting (preferably immersing) a treated product with a phosphate film in a zinc phosphate treatment solution and passing a relatively low-density current through it for a certain period of time, it is possible to This is an attempt to form a film by passing an electric current through the areas where it is difficult to chemically form (the spaces between the crystals), thereby improving the corrosion resistance of the phosphate film and the painted surface. It was found that the results improved.

The present invention was completed based on this knowledge, and its gist is that while bringing a treated product subjected to film formation with a phosphate treatment solution into contact with (preferably immersing) in a zinc phosphate treatment solution,
The present invention relates to a method for post-treatment of a phosphate film, characterized in that the treatment is carried out by applying an alternating current or a direct current.

The treated products subjected to film formation with the above phosphate treatment solution, which is the target of the method of the present invention, are treated by the usual spray method, spray treatment, etc.
Refers to a chemical conversion film formed by one or more of iron phosphate film, zinc phosphate film, calcium phosphate film, and manganese phosphate film by dipping method or dipping method.

The above zinc phosphate treatment solution that can be applied to the method of the present invention is:
This is a normal treatment liquid used to chemically coat iron and zinc steel sheets.To give an example, it has the following composition, and usually has a pH of 2. It has a value of 0 to 4.0.

Zinc ion...0.05~1.
0% calcium ion...0~1.
0 nickel ion...0~0.2
Manganese ion...0-0.1 Sodium ion...0.1-1.0
Phosphate ion...0.3-2
．． 0 nitrate ion...0~2.
0 chlorate ion...0~0.4
0 Chlorine ion...0-0.30 Nitrite ion...0-0.003 Organic carboxylic acid...0-0.05 In addition, the operating temperature of such treatment liquid is: The temperature may be selected within the range of room temperature to 80°C, preferably 40 to 70°C.

The current used in the method of the present invention may be either a direct current or an alternating current, and the current density is 0.01 to 2 A/Dd.
And the current application time is 1 to 60 seconds.

Hereinafter, specific aspects will be explained. 1 When using DC current as the anode: Current density is 0.01 to 2 A/
Ddl is preferably 0.03 to 0.1 A/Ddl, and the current application time is selected within the range of 1 to 60 seconds, preferably 5 to 3 A/Ddl.

In this case, if the current density is less than 0.01 A/Dd or the current application time is less than 1 second, sufficient effects of the method of the present invention cannot be obtained; If it exceeds this, the base metal and phosphate coating of the treated material will be violently dissolved. i When the object to be treated is used as a cathode with direct current: Current density 0.05 to 2 A/Ddl, preferably 0.1 to 1
A/Ddl and the current application time may be selected in the range of 5 to (4) seconds, preferably 10 to 3 seconds.

In this case, if the current density is less than 0.05A/Dd or the energization time is less than 5 seconds, a sufficient rust prevention effect cannot be obtained, and even if the current density is 2A/d or the energization time exceeds 6.2. , no further rust prevention effect is achieved. 111
In the case of alternating current: current density 0.1 to 2 A/dbo, preferably 0.2 to 1 A
/di, and the energizing time is 5 to 6 times, preferably 10
It may be selected within the range of 2 to 3.

In this case, if the current density is less than 0.1A/Dd or the energization time is less than 5 seconds, sufficient rust prevention effect cannot be obtained, and even if the current density is 2A/Dd or the energization time exceeds 6.2, , no further rust prevention effect is achieved. According to the method of the present invention having the above-mentioned structure, in terms of corrosion resistance when unpainted, it has superior rust prevention power compared to the case of conventional chromium-based post-treatment. paint,
Corrosion resistance after painting with acrylic or melamine-based oil paints is significantly improved compared to when no post-treatment is performed, and better results are obtained than when chromium-based post-treatment is performed. ing.

Furthermore, surprisingly, even if poor film formation occurs during phosphate chemical conversion treatment (for example, formation of a full-color film or a yellow rust film), if the post-treatment of the method of the present invention is performed, the above-mentioned film can be improved. The parts with poor chemical conversion have been repaired and are recognized to exhibit the same anti-corrosion ability as the normal parts. To summarize the above,
It can be said that the method of the present invention has the following advantages.

1 short time (1 to 6 hours) and energy saving (a). 01-2
A/D77l) post-treatment can greatly improve the corrosion resistance of the phosphate film and painted surface.

2. Even if a chromium-based post-treatment method, which is disadvantageous in terms of pollution problems and wastewater treatment, is not adopted, higher corrosion resistance performance can be obtained by the method of the present invention.

3. Even if there are defects in film formation such as blue color and scratches during film formation, the property can be properly modified by the method of the present invention.

Next, the present invention will be specifically explained by giving Examples, Comparative Examples, and Reference Examples.

Example 1-1-3 Commercially available cold rolled steel (70 x 150 x 0.8T!Rln)
The test plate was heated at 60°C in a 2% by weight solution of a weakly alkaline degreaser (trade name: 1 Ridrin #75, manufactured by Nippon Paint Co., Ltd.).
Spray degreasing for 2 minutes with
．． 2%, NO3O. 6%, ClO3O. l5%, NO2
O. Total acidity 17.
Free acidity 0.7, toner value 1.4 (treatment liquid at 25C
Sample C, add a few drops of 50% H2SO4, and add 0.
The end point is the point at which the color changes from colorless to pale pink using a KMTlO4 solution of 0.04 titration, and is expressed as the number of ML required for titration)
A chemical conversion treatment is carried out by spraying at a temperature of 50°C for 2 minutes, followed by washing with tap water and drying.

Next, the obtained chemical conversion treatment board is immersed in a zinc phosphate chemical treatment solution with the same composition as above (total acidity, free acidity, Naner value, and temperature are also the same), and post-treatment is carried out by applying electricity under the conditions shown in Table 1. After that, it is washed with water and then dried.

In this way, a post-treated plate is obtained. Comparative example 1 The chemical conversion treated board of Example 1 (no post-treatment) was used.

Comparative Example 2 The chemical conversion treatment board of Example 1 was treated with a chromic acid-based post-treatment agent (trade name 1 Deoxylite #41J manufactured by Nippon Paint Co., Ltd.).
The plate is post-treated by immersing it in a 0.1 volume % solution at a temperature of 35°C for 3α seconds, followed by washing with water and then drying to obtain a post-treated plate. Reference Example 1 Each of the treated plates of Example 1 1 to 3 and Comparative Examples 1 and 2 was coated with acrylic resin powder coating 'Pr (trade name 1 Powdax A-32 White J manufactured by Nippon Paint Co., Ltd.). Coating thickness 6
Coat at 0μ and bake in two coats at 175°C.

A 5% salt spray test (JIS-Z-2371) was conducted on the above test plates (unpainted plate and coated plate), and the results are shown in Tables 2 and 3.

In the note table, ◎ indicates rust occurrence area 0%, O is less than 10% of the rust occurrence area, Δ is less than 50% of the rust occurrence area, × indicates rust occurrence area of 80% or less; XX indicates the rusted area is 100% or less.

Example 2, 1 to 3 A test plate of commercially available cold-rolled steel (70 x 150 x 0.8 W 71) was heated in a 2% by weight solution of a weakly alkaline degreaser (trade name: 1 Ridrin #75, manufactured by Nippon Paint Co., Ltd.). Spray degreasing at 60°C for 2 minutes, then wash with water, and then apply zinc phosphate chemical conversion treatment solution (ZnO.lO%, NlO.OO4%, PO4
l. 4%, NO3O. 5%, ClO3O. l%, ClO
．． l%, NO2O. Total acidity: 1.0%, free acidity: 0.00% (OO65%) & Toner value 1.5, temperature 500C, pre-spray for 15 seconds and immersion for 2 minutes (the latter 1' is energized under the conditions shown in Table 4), and after chemical conversion treatment and post-treatment, Wash with water and then dry.

Comparative Example 3 The same cold rolled steel test plate as in Example 2 was subjected to spray degreasing, water washing, and chemical conversion treatment (press spray for 1 second and immersion for 2 minutes) using the same treatment agent and treatment conditions, and then washed with tap water.
Then dry.

Reference Example 2 A polyester electrocoating paint (1) manufactured by Hon Paint Co., Ltd., product name 1 Power Coat 9600KJ) was applied to each of the treated plates of Example 2 1 to 3 and Comparative Example 3 at a coating thickness of 20 μm, Baking was performed at 170°C for 3 minutes.

A 5% salt water spray test (JIS-Z-2371) was carried out on the above electrocoated test plates, and the results are shown in Table 5. Example 3-1 to 3 A commercially available cold-rolled 814 (70X150X0.8?) test plate was heated in a 2% by weight solution of a weakly alkaline degreaser (1) manufactured by Hon Paint Co., Ltd. under the trade name 0 Ridrin #75. 60°C
Spray degreasing for 2 minutes at Dry after washing with water.

As a result, the film became blue-collar and poor. Next, using the obtained chemical conversion treatment plate, apply a post-treatment liquid. and post-treatment conditions are the same as in Example 1. In addition, Example 3
The energization conditions 1 to 3 correspond to 1 to 3 of the first embodiment, respectively. Comparative Example 4 The chemical conversion treated board (post-treated) of Example 3 was used.

Comparative Example 5 The chemical conversion treated board of Example 3 was treated with a chromic acid post-treatment agent (trade name: 0 Deoxylite #4L, manufactured by Nippon Paint Co., Ltd.).
．． The plate is post-treated by immersing it in a 1 volume % solution at a temperature of 35° C. for 3 hours, followed by washing with water and then drying to obtain a post-treated plate. Reference Example 3 Each of the treated plates of Example 3 1 to 3 and Comparative Examples 4, 5, and 1 was coated with an acrylic resin oil-based paint (trade name: 1 Super Lac E-41 White, manufactured by Nippon Paint Co., Ltd.) with a film thickness of 40 μm. Coat at 150°C and bake in two batches at 150°C.

Claims (1)

[Scope of Claims] 1. A phosphate film characterized in that the treatment is carried out by applying an alternating current or direct current to a treated portion that has been chemically formed with a phosphate treatment solution while bringing it into contact with a zinc phosphate treatment solution. Post-processing method. 2. The method according to item 1 above, wherein the method is immersed in a zinc phosphate treatment solution having a pH of 2.0 to 4.0 and is energized for 1 to 60 seconds at a current density of 0.01 to 2 A/dm^2. 3 AC current with a current density of 0.1 to 2 A/dm^2
The method described in item 1 above, in which electricity is applied for 60 seconds. 4 Current density 0.01 to 0.2 A/ using the treated material as an anode
The method according to item 1 above, wherein a direct current of dm^2 is applied for 1 to 60 seconds. 5 Current density 0.05 to 2 A/dm using the treated object as a cathode
The method according to item 1 above, in which a DC current of ^2 is applied for 5 to 60 seconds.