| abstract |
An aqueous base treatment composition for a coated steel sheet that forms a base treatment layer that provides excellent corrosion resistance under the eaves while sufficiently ensuring processing adhesion without containing chromium. In a base treatment composition containing a specific organosilicon compound, a hexafluorometal acid, a urethane resin having a specific cationic group, a vanadium compound, and an aqueous medium, the cationic group of the urethane resin and When the total amine value has a specific value, a ground treatment layer that provides excellent corrosion resistance under the eaves while sufficiently securing processing adhesion can be obtained. [Selection figure] None |