SURFACE-TREATED STEEL SHEET WITH HIGHLY CORROSION RESISTANT ORGANIC COATING

摘要

PROBLEM TO BE SOLVED: To obtain a surface-treated steel sheet which does not contain chromium, has excellent corrosion resistance and excellent lubricity as well. SOLUTION: This surface-treated steel sheet is formed by controlling steel sheet roughness in such a manner that the thickness (A) of the film on the projecting parts of the plated steel sheet roughness attains >=30% of the thickness (B) of the film on the recessed parts of the plated steel roughness and applying the organic film not containing Cr on such steel sheet. Accordingly, the corrosion resistance film better than the film of the conventional chromate system is obtained by coating the plating surface layer controlled in the surface layer ruggedness with the organic film containing a thiocarbonyl compound and organic and/or inorganic phosphoric acid ions or further containing water dispersible silica therein may be obtained. The surface-treated steel sheet with which good pressing workability is assured and which has corrosion resistance and the pressing workability in combination may be obtained by further adding a lubricant thereto.