JPS61257270A - Treatment of zinc film surface - Google Patents

Abstract

PURPOSE:To obtain the superior sticking property and anti-corrosiveness against a zinc surface by coating the zinc-plated film surface with the paint composition containing a thermoplastic resin and an anti-corrosive pigment. CONSTITUTION:In the treatment of the zinc film surface, an ordinary temperature drying-type paint containing a thermoplastic polyamide and an anti-corrosive pigmentm, further compounding a hard resin as desired is coated on the zinc-plated film surface. In such a manner, the water-proof property and adhesive property of the film are remarkably improved by combining the polyamide resin with the anti-corrosive pigment, and more improvement is made by compounding the hard resin. Accordingly, the superior sticking property and anti-corrosiveness against the zinc surface can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a method for treating the surface of a galvanized coating. The present invention relates to a method for treating the surface of a zinc coating, which is applied to the surface of a plating coating and is intended to obtain excellent adhesion and anticorrosion properties to the zinc surface.

BACKGROUND OF THE INVENTION As a long-term corrosion protection method for steel materials or steel products, galvanizing or painting with zinc-rich paints has been used, and large structures such as power transmission towers are coated with hot-dip galvanizing. These zinc surfaces are consumed by water and the atmosphere, so to prevent this, oil-based paints or synthetic resin paints are usually applied.

However, oil-based paints have the disadvantage that they react with zinc to form metal soaps, leading to early peeling of the paint film. Treatment with a wash primer paint whose main component is butyral resin cannot be a stable treatment as the adhesion strength varies depending on conditions during painting such as humidity, drying time, and film thickness.

Painting with chlorinated rubber paint gives relatively good effects.

However, steel corrosion due to dehydrochlorination of chlorinated rubber becomes a problem in the non-plated parts that come into contact with steel materials. Amine-cured epoxy paints do not have such problems, but they are dissatisfied with handling because they are two-component paints and dry poorly at low temperatures. As described above, all of the techniques that have been proposed as methods for treating galvanized coatings have problems, and there is a need for an easy and reliable treatment method.

Problems to be Solved by the Invention Therefore, we have created a paint that has excellent adhesion to galvanized coatings, does not react with zinc, and also exhibits excellent anti-corrosion properties even on unplated iron surfaces. It is an object of the present invention to provide a simple treatment method for preventing corrosion of galvanized surfaces by using a material that has good drying properties and flexibility.

Means for Solving the Problems According to the present invention, the above object is characterized in that the surface of the galvanized film is coated with a room-temperature-drying paint containing thermoplastic polyamide and anti-corrosion pigments, and optionally containing hard resin. This can be achieved by a method for treating the surface of a galvanized coating.

The thermoplastic polyamide resin used in the present invention is a condensate of polycarboxylic acid and polyamine, and has a molecular weight of 4,000 to 12
000, relatively low, softening point 80-150℃, acid value 10
The following refers to a resin that is solid at room temperature and is known as a thermoplastic polyamide with an amine value of 8 or less, such as Persamide 930.
．． 94o (Henkel Hakusui): Parsalon 111f, 11
29.1128, DPXJ50. DPX802.830
(Henkel Hakusui); Sanmide 550'-D, 553,
There are various commercially available products such as HT140E (Sanso Kagaku), and any of them can be suitably used.

The present inventors have found that when the above polyamide resin is combined with anti-corrosion pigments, it very unexpectedly provides a film with improved water resistance and adhesion, and especially when hard resin is blended, the water resistance and adhesion are improved. A further improvement in 1. We have discovered scales that provide excellent corrosion resistance in both plated and non-plated areas.

As the rust preventive pigment, any rust preventive pigment that is normally used for heavy duty corrosion protection is used, such as red lead, cyanamide lead, cyanamide zinc, synchromate, strontium chromate, zinc phosphate, aluminum tripolyphosphate, and tribasic sulfuric acid. Metal compounds such as lead, zinc oxide, calcium zinc cyanamide, aluminum molybdate, basic lead chromate are advantageously used.

In a preferred embodiment of the present invention, the hard resin used with the above components has a softening point of 10"c'h as known in the industry.
Examples of hard resins that are solid at room temperature after i.

A paint solvent, pigments (coloring pigments, extender pigments), etc. are added to the coating composition used in the present invention, which consists of a polyamide resin, a rust-preventing pigment, and a hard resin added as desired. It is applied by a method such as an airless coating method, and the anti-rust coating is applied by drying at room temperature.

The resin vehicle of the composition can be composed only of polyamide resin, and when hard resin is blended, it is preferable that the polyamide resin accounts for 50% or more of the resin component. However, in the latter case, the object of the present invention can be achieved by using polyamide resin in an amount of 30% or more of the total resin amount.

In this way, in the treatment method of the present invention, a paint containing polyamide resin as the main vehicle is used, and since the resin does not contain ester bonds, it does not generate zinc soap, and it is also resistant to decomposition such as dehydrochlorination. Since it is a stable resin, it can also be applied to unplated steel surfaces. In addition, polyamide resin exhibits particularly excellent adhesion to iron and galvanized surfaces.
Because it has a low Tg and is highly flexible, it can easily adhere to the deformation of the object to be coated, and when used in combination with a rust-preventing pigment, it exhibits excellent corrosion resistance.

Therefore, the present invention exhibits excellent protection and anticorrosion effects on zinc, galvanized surfaces, and zinc-rich paint coated surfaces, further advances the state of the art, and constitutes an extremely useful invention industrially.

The present invention will be explained below with reference to Examples. Parts and percentages are by weight unless otherwise specified.

Example 1 Anticorrosive paint No. 1 was prepared according to the conventional method using the following formulation.

Weight part DPX-550'7 Varnish 1) 24 Hytanol 1002 Varnish 2) 24 Cyanamide Lead 10 Tal
the law of nature
15 risi -
15 pheasant roll
9 isopropyl alcohol 3 cups
Total 100 Note 1) 50% of DPX-550 (polyamide resin, manufactured by Henkel Hakusui Co., Ltd., amine value 1, acid value 3, softening point 100°C)
Solution, solvent, xylol/isopropanol 3/1 2) 50% solution of Hytanol 1002 (alkylphenol resin, manufactured by Hitachi Chemical), solvent xylol/isopropanol 3/1 -300
25PG2G) and (J l5-G-33025PG
3S) by the ester coating method to a thickness of 60 to 70μ, and air-dried for several days.

Example 2 The same method as in Example 1 was applied to anticorrosive paint No. of the following composition.

2 was used.

Sanmide 5500 Varnish 3) 24 Ester Gum 105 Varnish 4) 24 Zinc Phosphate ZP-8B S> 10 Talli
15 risi -
15xO-l
9 Isopropanol 3 Total 100 Note 3) Amine value 3>, acid fiii7>, softening point 110°C
polyamide resin, 50% (Kijirol/Isopropanol 3/1) solution manufactured by Sanso Kagaku Co., Ltd.

4) Ester gum, 50% (xylol/isopropanol 3/1) solution manufactured by Arayo Kogyo Co., Ltd.

5) Manufactured by Kikuchi Color Co., Ltd. Example 3 The same method as in Example 1 was applied to anticorrosive paint No. of the following composition.

It was carried out using 3.

DPX-550 Varnish 48LF Bossei P
M3000 6) 10 tal
15 risi -
1
5 Kijirol 9 Isopropanol 3 Total
100 Note 6) Manufactured by Kikuchi Color Industries, Ltd. Comparative Examples 1 to 3 The same method as in Example 1 was carried out using the following coating composition.

Comparative Example I DPX-55048 Taruri 25 Rishi - 15 Kijiroll
9 Isopropanol 3 Comparative Example 2 Wash Primer (Vinyrex Active Primer A/P110 Nippon Paint ■) JIS-Ni-56272 Type A (FZ Pu5 Imaichi Nippon Paint ■) Comparative Example 3 Epoxy Primer (Hibon 20 Ace Nippon Paint @) The following tests were carried out on each of the galvanized steel sheets subjected to the above treatment, and the results are shown in Table 1.

Adhesion: Four 5 x 51 squares were cut into the paint film to reach the substrate, adhesive cellophane tape was pasted on the squares, and the condition was examined when the tape was removed.

(A) Adhesion after 500 hours of salt spray test (B) 20
℃ Tap water immersion Adhesion after 30 days (C) Dew condensation test Temperature cycle of 30℃ and 50℃ (2
(hourly) Adhesion after 1000 hours (D) Natural backlash Adhesion after 1 year (E) Flexibility Flexibility was evaluated by J Is-5400, good performance with diameter 10Ill...O poor... × (blank space below) Procedural amendment (voluntary) December 5, 1985

Claims (1)

[Claims] A method for treating the surface of a galvanized coating, which comprises applying a room temperature drying paint containing a thermoplastic polyamide and an anti-corrosion pigment and optionally a hard resin to the surface of the galvanized coating.