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(11) | EP 4 353 877 A3 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | SURFACE TREATMENT METHOD OF GALVANIZED STEEL SHEET PRODUCT AND GALVANIZED STEEL SHEET PRODUCT TREATED BY THE SAME |
| (57) There is disclosed a surface treatment method of a steel sheet formed product including
a first step of preparing a galvanized steel sheet formed product; a second step of
performing surface-modification treatment for a galvanized layer of the prepared steel
sheet formed product; a third step of coating a resin on the surface-modification-treated
galvanized layer; and a fourth step of bring the resin coating layer into close contact
on the galvanized layer. The second step may include a process of increasing a surface
roughness by electrolytically etching the galvanized steel sheet formed product in
a surface treatment composition solution. The surface treatment composition may be
an eco-friendly baking soda solution, and the baking soda solution may be prepared
by dissolving 10wt% to 50wt% of baking soda in water. The electrolytic corrosion may
be performed by using the galvanized steel sheet formed product as an anode and lead
or copper as a cathode, and the electrolytic corrosion may be performed by a voltage
of 10V to 36V DC at a temperature of 60°C to 85°C. The third step may perform a process
of re-coating a resin by general coating once or twice or more on the base steel sheet
coated with a resin by a first electrodeposition coating.
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