| abstract |
The present invention provides a chromium-free surface treatment solution capable of forming a film excellent in corrosion resistance, solvent resistance, coating property after alkali degreasing, and sweat resistance on a metal material surface at a bent portion of a steel plate. A resin compound having a specific bisphenol skeleton, a cationic urethane resin emulsion, a silane coupling agent, an organotitanium chelate compound, a tetravalent vanadyl compound, a molybdate compound, a fluorine compound, and water in a predetermined ratio. It mix | blends and pH is set to 4-5. [Selection figure] None |