| 摘要 |
PROBLEM TO BE SOLVED: To produce a galvanized steel sheet good in all of press-formability, weldability, adhesion and chemical convertibility by inexpensive and simple treatment. SOLUTION: The surface of a galvanized steel sheet is coated with an aq. soln. of pH 1 to 7 contg. phosphoric acid and hydrogen peroxide in such a manner that the weight ratio of phosphoric acid/H2O2 is controlled to the range of 0.1 to 10, and without executing water washing, it is baked at 50 to 300 deg.C and dried to form a phosphorous oxide based inorganic film of 10 to 500 mg/m2 coating weight expressed in terms of the P content which has a network structure composed of a P-O-P bond and substantially does not contain crystallization water.
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