| 摘要 |
PURPOSE:To produce a surface treated steel sheet having excellent corrosion resistance, etc., by successively forming an underlying chromate layer, coating type chromate film and org. resin film on the surface of the Zn plated steel sheet in a manner as to satisfy specific conditions. CONSTITUTION:Zn plating or Zn alloy plating is deposited to about 5-80g/m<2> on the surface of the steel sheet to form the 1st layer. A reaction type chromate or electrolytic chromate film as the underlying chromate layer is formed on the plated surface to form the 2nd layer. The coating type chromate film is further formed as the 3rd layer thereon. The chromate deposition is made 3-250mg/m<2> in terms of the amt. of chromium in total of the 2nd and 3rd layer. The chromate deposition of the 3rd layer is made >=1mg/m<2>. The free hexavalent chromium is deposited at 3-30wt% by the total chromium deposition. The org. resin film consisting of an arcylic resin, etc., as the 4th layer is formed at 0.3-2g/m<2> deposition and about 5-40wt% silica is preferably incorporated therein. The steel sheet having excellent fingerprint resistance, paintability, corrosion resistance in flawed parts, workability, etc., is thus obtd.
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