HIGHLY CORROSION RESISTANT SURFACE TREATED STEEL SHEET, AND PRODUCTION METHOD THEREFOR

摘要

PROBLEM TO BE SOLVED: To provide a surface treated steel sheet which exhibits excellent corrosion resistance without incorporating chromium into a surface film. SOLUTION: A film of a surface treatment composition is formed on the surface of a galvanized steel sheet or the like. The film comprises :(a) an aqueous epoxy resin dispersion solution of resins obtained by reacting a polyalkylene glycol-modified epoxy resin obtained by reacting polyalkylene glycol of a specified molecular weight, a bisphenol type epoxy resin, an active hydrogen-containing compound and a polyisocyanate compound, an epoxy group-containing resin, and a active hydrogen-containing hydrazine derivative; (b) a silane coupling agent, and; (c) phosphoric acid and/or a hexafluoro metal acid. Then, an upper layer film wherein the main component consists of a reaction product between a film forming organic resin and an active hydrogen-containing compound in which part or the whole consists of a hydrazine derivative containing active hydrogen is formed on the upper layer thereof. COPYRIGHT: (C)2004,JPO