SURFACE TREATMENT LIQUID FOR PLATED STEEL SHEET TO BE HOT-PRESSED

摘要

The present invention is a surface treatment liquid with excellent storage stability and is able to provide a surface-treated steel sheet for which the treatment coating formed has excellent water resistance, solvent resistance, adhesion to plated steel sheets, and hot lubricity as well as chemical conversion treatability after hot-pressing, corrosion resistance after coating, and spot weldability. The surface treatment liquid for a plated steel sheet that is to be hot-pressed comprises an aqueous ZnO dispersion (A) and a water-dispersible organic resin (B). The aqueous ZnO dispersion (A) comprises water and ZnO particles, the particle diameter of which is 50-300 nm. The water-dispersible organic resin (B) has an acid value of 5-45 mg KOH/g and 5-300 nm emulsion particle diameter. The mass ratio (WA/WB) of the mass (WA) of ZnO particles in the aqueous ZnO dispersion to the mass (WB) of solids of the water-dispersible organic resin is 30/70 to 95/5.