| abstract |
A highly corrosion-resistant, surface-treated steel sheet which has in order a zinc or zinc alloy deposit as an undercoating deposit, a chromate coating, and a coating of resin composition comprising a base resin obtained by adding at least one basic nitrogen atom and at least two primary hydroxy groups to the terminal of an epoxy resin, silica, and a difficultly soluble chromium compound. This resin composition has predetermined weight ratios of base resin/silica, base resin/difficultly soluble chromium compound, base resin/(silica + difficultly soluble chromium compound), and silica/difficultly soluble compound. The coating of this resin composition may contain a polyisocyanate compound as a hardener and further a silane compound as a crosslinking agent between the base resin and silica. |