Coating compositions for gavanized steel sheets and gavanized steel sheets treated with them

摘要

PURPOSE: A surface treatment composition for galvanized steel sheet having superior corrosion resistance, coherence property and low temperature drying property, and the galvanized steel sheet treated with the surface treatment composition are provided. CONSTITUTION: The surface treatment composition for galvanized steel sheet comprises 80 to 50 wt.% of a mixed resin in which aqueous organic resin and inorganic component are mixed in a solid ratio of 70:30 to 30:70, 10 to 40 wt.% of phosphate based corrosion resistance rust inhibitor of metal oxides and 1 to 20 wt.% of organic metal complex compound by solid mass of the surface treatment composition for the galvanized steel sheet, wherein the aqueous organic resin is selected from aqueous or water dispersed acrylic polymer resin having hydroxyl group or carboxyl group, epoxy resin, or a mixture thereof, the inorganic component is selected from alumina sol, silica sol, titania sol, zirconia sol, or a mixture thereof, the phosphate based corrosion resistance rust inhibitor of metal oxides is selected from phosphate solution of aluminum, aluminum polyphosphate, manganese, zinc, molybdenum and fluorine, phosphate solution of hexaammonium heptamolybdate tetrahydrate, phosphate solution of soda, or a mixture thereof, and the organic metal complex compound is selected from silane based coupling agent, titanium based coupling agent, zirconium based coupling agent, or a mixture thereof.