| 摘要 |
PURPOSE: To develop a thin film organic composite steel sheet excellent in appearance, corrosion resistance and lubricious film adhesion by laminating a chromate film having a specified compsn. and an organic film on the surface of a galvanized steel sheet. CONSTITUTION: On the surface of an electrogalvanized steel sheet, as a primary layer, a chromate film contg. CrO3 , in which the ratio of CrO3 /whole Cr is regulated to 0.1 to 0.8, a phosphoric acid compound by 0.5 to 2.0 weight ratio to CrO3 and collodal silica in which the major axis is regulated to 10 to 100nm and the ratio of the major axis/minor axis is regulated to >=10 by the weight ratio of 1 to 4 to CrO3 is formed by the quantity of 10 to 60mg/m. Successively, on the surface, as a secondary layer, an organic film contg. silica having 3 to 30nm grain size by the ratio of 10 to 40% in epoxy resin and the one obtained by modifying epoxy resin into amines, urethane resin, acrylic resin and the ones obtained by modifying those into epoxies is laminated by the quantity of 0.3 to 5g/m<2> to produce the high corrosion resistant surface treated steel sheet excellent in various characteristics.
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