Abstract: A paint composition containing a corrosion inhibitor A prepared from porous silica particles, to which Ca ion is bonded by ion-exchange, and a polyphosphate B preferably at an A/B weight ratio of 60/40 to 5/95 and at an A+B ratio of 5-150 parts by weight based on 100 parts by weight of resinous components. A base metal sheet is preferably one pre-treated with a chemical agent containing at least one fluoroacid. Since the polyphosphate B controls dissolution of Ca ion, an effect of Ca ion on corrosion inhibition is maintained over a long term. The painted metal sheet does not put harmful influences on the environment, since it does not contain chromium compounds.

Abstract: Newly proposed paint composition contains a corrosion inhibitor A prepared from porous silica particles, to which Ca ion is bonded by ion-exchange, and a polyphosphate B preferably at an A/B weight ratio of 60/40 to 5/95 and at an A+B ratio of 5-150 parts by weight based on 100 parts by weight of resinous components. A base metal sheet is preferably one pre-treated with a chemical agent containing at least one fluoroacid. Since the polyphosphate B controls dissolution of Ca ion, an effect of Ca ion on corrosion inhibition is maintained over a long term. The painted metal sheet does not put harmul influences on the environment, since it does not contain chormium compounds.