| abstract |
A chromium-free aqueous liquid surface treatment agent that can impart both a good corrosion resistance and a good paint adherence to zinciferous-plated steel sheet contains as its essential components polyhydroxyaryl carboxylic acid and/or depside thereof and silane coupling agent with the formula (YR)mRnSiX(4-m-n), in which R denotes alkyl groups; X is the methoxy or ethoxy group; Y is the vinyl, amino, mercapto, glycidoxy, or methacryloxy group; m = 1 to 3; and n = 0 to (3-m). The total content of said essential components is preferably 1 to 50 weight %. |