PURPOSE: To provide a water point coating compsn. for chromate-treated galvanized steel sheets, which has excellent water resistance, adhesion, etc., consisting of an org. amine salt of an oil-free alkyd resin contg. tannic acid as a component and a water-dispersible blocked isocyanate compd.
CONSTITUTION: A polyhydric alcohol, 1W20wt% tannic acid, a polycarboxylic acid such as phthalic acid, and, if necessary, a monocarboxylic acid are subjected to an esterification reaction to prepare an oil-free alkyd resin having an acid value of 20W100KOHmg/g and a hydroxyl value of 50W250KOHmg/g, which is then neutralized with a neutralizing agent such as diethylamine or ammonia to obtain an org. amine salt or ammonium salt. Said org. amine salt or ammonium salt of said alkyd resin is mixed with a water-dispersible or water- soluble blocked isocyanate compd. in such a proportion as to give a ratio of hydroxyl groups in the resin to isocyanate groups of 1/1.3W1/0.5.
SASAKI HIROJI
HIGUCHI YOSHIHIRO
