METHOD OF PRODUCING INORGANIC COATED GALVANIZED STEEL SHEET EXCLLENT IN PRESS FORMABILITY

摘要

PROBLEM TO BE SOLVED: To produce a galvanized steel sheet having good stamping property, weldability, bondability and chemical conversion property by a inexpensive and simple treatment. SOLUTION: The surface of a galvanized steel sheet subjected to pretreatment by alkali dipping and/or acid dipping is coated with a aqueous solution of pH 1 to 7 containing phosphoric acid and H2O2 in such a manner that the weight ratio of phosphoric acid/H2O2 lies in the range of 0.1 to 1, which is baked at 50 to 300 deg.C and dried without executing water washing to deposit a phosphorous oxide series inorganic film which does not substantially contain crystallization water.