SURFACE-TREATED STEEL SHEET

摘要

Disclosed is a surface-treated steel sheet having a surface treatment film containing a metal compound containing titanium, a metal compound containing magnesium, a cationic urethane resin having at least one cationic functional group selected from primary to tertiary amino groups and quaternary ammonium salt groups, and a cationic phenol polycondensate having a cationic functional group, which is a polycondensation product between a phenol compound and an aldehyde. The titanium content in the surface treatment film is 1-4% by mass relative to the total solid content; the magnesium content in the surface treatment film is 0.2-2% by mass relative to the total solid content; the cationic urethane resin content in the surface treatment film is 20-35% by mass relative to the total solid content; and the cationic phenol polycondensate content in the surface treatment film is 25-40% by mass relative to the total solid content. The mass ratio between the cationic urethane resin and the cationic phenol polycondensate is from 33.3:66.7 to 49:51.