CR-FREE COATING MATERIAL FOR GALVANEELED STEEL SHEET REPRESENTING EXCELLENT IN ADHESION TO PAINTS AND CORROSION RESISTANCE AND A PROCESS FOR PRODUCING CR-FREE COATED STEEL SHEET USING THE COATING MATERIAL

摘要

A Cr-free surface treatment agent for galvannealed steel sheets which are excellent in various characteristics, and have superior anti-rust properties and formability after degreasing and painting processes is provided, and a method for manufacturing steel sheets with various characteristics such as corrosion resistance and powder paintability by applying the surface treatment agent to galvannealed steel sheets is provided. A metal surface treatment composition comprises: 30 to 80 weight parts of an acryl-olefin-urethane mixed resin as a water-soluble organic resin based on the total solid content of 100; 10 to 40 weight parts of silica as an inorganic binder; 0.5 to 2 weight parts of a solid content of water-soluble vanadium phosphate as an anti-rusting and corrosion resisting agent; 2 to 20 weight parts of tetra normal butyl titanate as a metal chelating agent; and 0.5 to 10 weight parts of water dispersed carbodiimide as a water soluble hardener. The tetra normal butyl titanate is replaced with a mixture of aminoalcohol titanate and glycidyl silane. The acryl-olefin-urethane mixed resin is replaced with acryl-olefin.