JPS5838508B2 - Surface treatment method for iron, steel or zinc and their alloys - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a surface treatment method for iron, steel, zinc, and their alloys, and in particular to a post-treatment cleaning method after phosphoric acid coating, which provides a coating base coating with excellent corrosion resistance and paint film adhesion. It is intended to provide.

Conventionally, as a pre-treatment for metals to be painted or as a temporary anti-corrosion treatment without painting, metals are treated with a phosphate film or oxide film and then washed with a dilute chromic acid solution to prevent metal corrosion and painting. It is known to be effective in preventing surface appearance deterioration.

Post-treatment cleaning with chromic acid solution is often impossible to actually use unless there is sufficient wastewater treatment equipment, as this liquid is toxic and poses a pollution problem, and its waste disposal is troublesome. In addition to the above-mentioned problems, post-treatment cleaning with acid solutions has disadvantages such as the fact that for some types of paint systems, even though chromic acid treatment is not used, the effect is hardly recognized and the paint film turns yellow. was there.

In addition, when the painted surface of iron, steel, zinc, and their alloys is deformed, peeling may occur between the phosphate coating or chromate coating on the surface of iron, steel, zinc, and their alloys, and the paint film. There were drawbacks such as a decrease in the corrosion resistance of the coating film.

In order to eliminate these drawbacks, the present inventors conducted various studies and found that the surface of iron, steel, zinc, and their alloys was subjected to phosphate chemical conversion treatment, and the surface was Valent chromium ion 0.05-20? /l, and one or two selected from the group of 2 to 6 linked phosphate esters of myo-inositol or salts thereof, tannin or tannic acid, and 1-hydroxyalkyl-1,1-diphosphonic acids. More than 0.1 to 20 species? The present invention was based on the discovery that a coating film that improves the corrosion resistance and adhesion of coatings after painting is formed on the surfaces of iron, steel, zinc, and their alloys by treating them with an aqueous solution containing completed.

The present invention is applied to the surfaces of iron, steel, zinc, hot-dip galvanized steel sheets, and electrogalvanized steel sheets, and these surfaces may be subjected to alkaline desaturation, pickling, and accompanying treatments by spraying or immersion as necessary. Cleaned by washing with water.

3 in the present invention by cleaning or not cleaning the metal.
The treatment is carried out with an aqueous solution containing valent chromium ions, or after phosphating, the aqueous solution containing trivalent chromium ions according to the present invention is used. It is preferable to treat with an aqueous solution.

When the metal is subjected to phosphate chemical conversion treatment, a phosphate film is formed on the surface of the metal after surface conditioning pretreatment with a colloidal titanium-containing liquid, and then washed with water, and then treated with trivalent chromium ions.
□ 2 to 6 linked phosphate esters of oinositol or salts thereof, tannin or tannic acid, and □ one or more selected from the group of -hydroxyalkyl-1゜1-diphosphonic acids. Treat with aqueous solution containing.

Water-soluble 3 that supplies trivalent chromium ions used in the present invention
Examples of valent chromium compounds include Cr2(SO4)3t
cr(H2PO4)3 tcrF3-3H20°Cr
Ct3t Cr (Ct03)2 j Cr(NO3)
3-9H2Q.

Cr(OH)3. Examples include chromium oxalate.

The concentration of trivalent chromium ion used is 0.05 to 20 f/Z, preferably 0.5 to 51/l.

0.05? / is less effective, 2 Of? /
It is not economical.

The 2-6 bonded phosphate esters of oo-inositol used in the present invention are myo-inositol silicate ester, □ oo-inositol triphosphate ester, myo-inositol tetraphosphate ester, □ oo-inositol pentaphosphate ester, and myo-inositol triphosphate ester. This refers to inositol hexaphosphate ester, and the alkali metals and alkaline earth metals of the 2 to 6 bonded phosphate esters of myo-inositol are bonded by the 2 to 6 bonded phosphate esters of myo-inositol. The hydrogen group of the phosphoric acid ester is Na,
It is a water-soluble salt substituted with a metal such as KtLi 2MgtcatsrtBa.

Myo-inositol hexaphosphate ester is commonly known as phytic acid and will be abbreviated as phytic acid hereinafter.

Furthermore, since myoinonthole di-pentalic acid ester is mainly obtained by hydrolyzing phytic acid, phytic acid is the most useful industrially.

Examples of the tannins or tannic acids used in the present invention include gepracho, debjit, Chinese tannic acid, Turkish tannic acid, hamamelitannic acid, kephric acid, sumac tannin, pentad tannin, and erlagic acid tannin.

1-hydroxyalkyl-11゜1- used in the present invention
Diphosphonic acid has an alkyl group with 1 to 6 carbon atoms.
It can also be used with salts.

1 of these phytate tannins or tannic acids, 1-hydroxyalkyl 1-2-diphosphonic acids
The concentration of the species or species used is 0.1 to 20 Y/l, preferably 0.5 to 5 g/l.

0, 1? If it is less than /, the effect will be small, and if it is more than 20g/, the performance will not change, but it will not be economical.

It should be noted that since phosphate treatment is performed before the trivalent chromium ion-containing aqueous solution used in the present invention, a phosphate treatment solution may be brought into the container.

The elements introduced are usually phosphoric acid, Ni, Zn, and cotT.
ItMntsiF6 etc. are mentioned.

The permissible amounts for mixing these elements include corrosion resistance,
It is sufficient as long as the adhesion is not hindered, and the amount should be 5?5 as a non-volatile content. /l, or less.

F- as a compound that can be added if necessary.

5IFa 2-2BF4”) TIF6”-2
ZrF62t phosphate root, boric acid root, colloidal silica,
These include alumina sol, water-soluble or water-dispersible organic polymer compounds, and the like.

The aqueous solution containing trivalent chromium ions used in the present invention is used on the acidic side, and the pH of this aqueous solution is 1.5 to 6.0.
It is preferably 3.0 to 5.0.

If the pH is below 1.5, the etching reaction will be severe and it will be difficult to obtain a good coating film.

In addition, in an acidic region of pH 6.0 or higher, the reaction is slow and it takes time to form a coating film with anticorrosion properties, which is not economical.

The conditions for using the aqueous solution used in the present invention include a known method such as dipping, spraying, and coating at a temperature from room temperature to the boiling point of the solution for a sufficient time to form a protective coating. .

By practicing the present invention, the coating film has good adhesion when the metal surface is deformed after painting, and the coating film obtained by the method of the present invention can also be used as a base for painting. It has superior coating adhesion and corrosion resistance compared to general-purpose chromate coatings, and it also prevents yellowing of the coating and can be dried without washing with water, so it is better than conventional chromate coatings. The problem of acid wastewater treatment has disappeared.

The present invention will be explained below with reference to Examples.

Example 1 Commercially available hot galvanized steel sheet (plating amount 20 Vm2) 0
．． After surface adjustment and phosphate treatment of 03X10X15, the sample was washed with water and treated with an aqueous solution containing trivalent chromium ions, and then squeezed with a roll and dried.

Phosphate film weight u 1.21? It was An2.

The processing conditions are as follows.

Surface conditioning treatment Phosphate treatment Treatment with an aqueous solution containing trivalent chromium ions Example 2 An aqueous solution containing trivalent chromium ions was treated with Cr2(SO4
)3 is 0.3? /l (Cr3+ conversion) and tannic acid (
Product name: Tannic acid AL, Fuji Chemical) 5? The process was carried out under the same conditions as in Example 1, except that the aqueous solution was changed to an aqueous solution containing 1/1 and adjusted to pH 3.5 with phosphoric acid.

Example 3 An aqueous solution containing trivalent chromium ions was converted into Cr2(SiF
6) 0.3 in 3? /l (in terms of Cr"') and 1-hydroxyethane-1,1-diphosphonic acid (trade name Coupinal SL, Henkel) O,5y7t, except that it was changed to an aqueous solution adjusted to pH 5 with aqueous ammonia. was treated under the same conditions as in Example 1.

Comparative Example 1 An aqueous solution containing trivalent chromium ions was converted into CrF32?
Filtrate solution (pH 3) containing only /l (Cr” equivalent)
) The treatment was carried out under the same conditions as in Example 1, except that the conditions were changed to

Comparative Example 2 Instead of an aqueous solution containing trivalent chromium ions, phytic acid 1 f/7. Tannic acid (trade name Tannic acid AL, Fuji Chemical) 5? / and 1-hydroxyethane-1,
1-diphosphonic acid (trade name Terpinal SL,
Henkel) 0.8? The treatment was carried out under the same conditions as in Example 1, except that the solution was changed to an aqueous solution (pH 3) containing /lA: and adjusted to pH 3.5 with aqueous ammonia.

Example 4 Commercially available electrogalvanized steel sheet (plating amount 20y/m2) 0
．． 03 X 10 X 15CnK After being treated with an aqueous solution containing trivalent chromium ions, it was squeezed with a roll and dried.

The processing conditions are as follows. Comparative Example 3 An aqueous solution containing trivalent chromium ions was mixed with CrF 30.
Aqueous solution (pH
The treatment was carried out under the same conditions as in Example 4, except that 43,5) was changed.

Comparative Example 4 The treatment was carried out under the same conditions as in Example 4, except that instead of the aqueous solution containing trivalent chromium ions, an aqueous solution (pH 3,5) containing only phytic acid 21/l was used.

Examples 1, 2, 3, 4 of the present invention. Alkyd melan paint (registered trademark Alacni 1 White, Kansai Paint) was applied to electrogalvanized steel sheets treated in Comparative Examples 1 and 23.4.
was applied using the barcode method, set for 20 minutes, and then baked in a hot air circulation oven at an ambient temperature of 140°C for 25 minutes to produce a coated board with a coating thickness of 30 ± 2 microns. The results of the tests and salt spray tests are shown in Table 1.

Test method: Paint film adhesion test ■) Goban test: After making scratches reaching from the painted surface to the substrate using an NT cutter in a square pattern of 1 mrn square, peel it off with cellophane tape and measure the number of remaining paint films. Give an evaluation score based on the number remaining/100.

The evaluation criteria are as shown below.

2) Erichsen test for scratches Similar to the test for scratches, after making scratches in the shape of scratches, extrude for 5 minutes using an Erichsen tester, peel off with a seven-layer tape, and calculate the number of remaining coatings as remaining number/100. Give an evaluation score.

The evaluation criteria are as shown below.

3) Impact test DuPont impact tester (center of impact 1/2 inch, load 500
1. After applying an impact to the coated surface with a falling distance of 50 cI'Il), peel it off with cello tape and give an evaluation score.

The evaluation criteria for paint film adhesion are as follows.

Therefore, the thicker the evaluation score, the better the coating film adhesion.

Salt water spray test 1゜ Painted board: After making cross-shaped scratches on the test board from the painted surface to the base using an NT cutter and conducting a salt water spray test based on JIS-Z-2371 for 120 hours, the painted surface was washed with water and dried. Then, remove it with cellophane tape and evaluate the peeling status of the painted surface.

The evaluation criteria are as shown below.

After conducting a salt spray test for 24 hours on a 2° unpainted board, the area where white rust has developed is evaluated and judged.

The evaluation criteria are as shown below.

Example 5 Commercially available hot dip galvanized steel sheet (zero spangle zinc coating amount 244 r/m2) 0.03X 10XI 5cm
After surface conditioning treatment and phosphate treatment, it was washed with water, treated with a solution containing trivalent chromium ions 1c, and then rolled and dried.

The processing conditions are as follows.

Surface conditioning treatment Phosphate treatment Example of treatment with trivalent chromium ion-containing solution 6 Commercially available hot-dip galvanized steel sheet (zinc coating amount 244
f/m2), and mixed an aqueous solution containing trivalent chromium ions with CrF31 y/z (in terms of Cr3+), tannic acid (trade name Tannic Acid AL, Fuji Chemical) I P/7, and phytic acid (Mitsui Toatsu Co., Ltd.). )0.5? The process was carried out under the same conditions as in Example 1, except that the aqueous solution containing 1/1 (purity equivalent) was used.

Comparative Example 5 An aqueous solution containing trivalent chromium ions was converted into a chromic acid-containing solution [trade name Percolene #62...Cr(OH)sO,
5S'/l (Cr conversion), CrOL2f? /1 (Cr conversion), pH 3 Nippon Parkerizing] 15? The treatment was carried out under the same conditions as in Example 5, except that the concentration was changed to /l.

The hot-dip galvanized steel sheets prepared in Examples 5 and 6 and Comparative Example 5 were coated with epoxy paint as a brimer coat using a bar coater method to a film thickness of 4 μm. After that, the hot-dip galvanized steel sheets were coated with a hot-air circulation system at an ambient temperature of 290°C for 50 seconds. Burnt.

Next, acrylic paint was applied as a top coat using a bar coater method to a film thickness of 12 μm, and the ambient temperature was 29°C.
It was baked for 50 seconds in a hot air circulation oven at 0°C.

After the coated board was prepared as described above, the test board was subjected to a paint film adhesion test and a salt spray test. The results are shown in Table 2. Paint film adhesion test method. After leaving it for 24 hours, fold it in half, tighten the folded part using a vise, apply cellophane tape to the folded surface, and rapidly peel off the tape.

After this test, an evaluation score will be given based on the peeled area of the paint film from the bend.

When tightening using a vise, the test conditions can be changed from severe conditions to more relaxed conditions by inserting a plate piece of the same thickness into the bent part.

Depending on the number of inserted plates, one is displayed as Ul-T, two is displayed as f12-T, and no plate is inserted as 10-T.

Therefore, the test conditions are more severe as the number of inserted plate pieces is smaller.

The evaluation criteria are as shown below.

Test result example 7 Commercially available iron plate (5PCCD) 0.08X7xl 5crn
After degreasing, washing with water, phosphate treatment, washing with water, treatment with an aqueous solution containing trivalent chromium ions, and then drying.

The processing conditions are as follows. Phosphate film weight tt
12.5? /m2.

Comparative Example of Treatment with an Aqueous Solution Containing Trivalent Chromium Ions Comparative Example 6 An aqueous solution containing trivalent chromium ions was treated with a chromic acid-containing solution [trade name Percolene #60...Cr(OH)aO10]
9P/1 (Cr conversion), Cry30.24? /1(C
r conversion), pH 3.5, Nippon Parkerisin 4.8?
The treatment was carried out under the same conditions as in Example 7 except that the concentration was changed to /l.

Example 8 Commercially available iron plate (5PCCD) 0.08x7xl 5Crn
After degreasing, the sample was washed with water, treated with an aqueous solution containing trivalent chromium ions, and then dried.

The processing conditions are as follows.

Degreasing treatment Comparative example of treatment with an aqueous solution containing trivalent chromium ions 7 An aqueous solution containing trivalent chromium ions was treated with CrF32,5
Aqueous solution containing only f/l (in terms of Cr3)
The treatment was carried out under the same conditions as in Example 8 except that H3,5) was changed.

Comparative Example 8 The aqueous solution containing trivalent chromium ions was treated under the same conditions as in Example 8, except that the aqueous solution (pH 3,5) containing only 2 g/l of phytic acid (pH 3,5) was changed.

The iron plates treated in Examples 7 and 8 and Comparative Examples 6, 7, and 8 were treated with polybutadiene electrocoating paint at a temperature of 30°C and a voltage of 250V for 3 minutes, and then electroplated to a film thickness of 25□. After coating, bake in a hot air circulation oven at an ambient temperature of 170°C for 30 minutes, then spray coat with Amirac intermediate paint (manufactured by Kansai Paint) to a film thickness of 35 microns, and bake at 130°C for 20 minutes. The results of the following paint film adhesion test and salt water spray test were conducted on a painted board that was coated with Amirac topcoat paint (manufactured by Kansai Paint) using a spray method to a film thickness of 35 square meters and baked at 130°C for 20 minutes. It is shown in Table 3.

Test method Salt water spray test The test was carried out under the same conditions as in Example 1 except that the spray time was changed to 250 hours.

Paint film adhesion test The above-painted test plate was placed in a constant temperature room at 250° C. for 24 hours, then bent to a 1800° angle using an iron rod with a radius of 5 rran as a support, a cellophane tape was attached to the bent surface, and the tape was rapidly peeled off.

After this test, evaluate and judge the peeling status of the coating film on the bent surface.

The evaluation criteria are the same as in Examples 5 and 6.

Test results

Claims (1)

[Claims] 1 The surface of iron, steel, zinc, and their alloys is subjected to phosphate chemical conversion treatment 1 to 1 or without phosphate chemical conversion treatment, and the surface is treated with trivalent chromium ions of 0.05 to 20? /l and □2 to 6 linked phosphate esters of oinositol or salts thereof,
Tannin or tannic acid and 1-hydroxyalkyl-
One or more selected from the group of 1,1-diphosphonic acids σ) 0.1 to 20? A surface treatment method for iron, steel, zinc, and alloys thereof, characterized by treating with an aqueous solution containing /l.