| 摘要 |
PROBLEM TO BE SOLVED: To obtain a surface treated steel sheet safe and harmless in the producing process and also in the use and moreover having excellent corrosion resistance. SOLUTION: A plated steel sheet is treated with an acidic aq. soln. of pH 0.5 to 5 contg. (a) silica and/or a silica sol. by 0.001 to 3 mol/L as the content of SiO2, (b) phosphoric acid ions and/or phosphoric acid compds. by 0.001 to 6 mol/L expressed in terms of P2O5 and (c) one or more kinds selected from the groups of any metallic ions among Al, Mg, Ca, Sr, Ba, Hf, Ti, Y, Sc, Ce, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Lu, Ni, Co, Fe and Mn, water soluble ions contg. at least one kind among the metals, oxide contg. at least one kind among the metals and hydroxide contg. at least one kind among the metals by 0.001 to 3 mol/L in total expressed in terms of the metallic contents of the metals and is thereafter heated and dried to form a chemical conversion film of 0.005 to 2μm on the surface of the plated steel sheet.
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