HIGHLY CORROSION RESISTANT SURFACE TREATED STEEL SHEET

摘要

PROBLEM TO BE SOLVED: To provide a chromium-free surface treated steel sheet capable of obtaining excellent corrosion resistance. SOLUTION: A surface treatment film by a composition comprising: a water base epoxy resin-dispersed liquid obtained by adding an active hydrogen-containing hydrazine derivative or the like to a specific polyalkylene glycol modified epoxy resin; a silane coupling agent; and phosphoric acid or hexafluorometal acid is formed on the surface of a galvanized steel sheet or the like. An upper layer film by a composition obtained by blending a specific cross linking agent into a resin obtained by modifying a specific epoxy resin with a soft component and further bringing the same into reaction with a hydrazine derivative is formed on the upper layer thereof. By the composite action between the surface treatment film in the upper layer and the upper layer film, particularly excellent worked part corrosion resistance can be obtained. COPYRIGHT: (C)2009,JPO&INPIT