Masterchem Industries 41125 Hammered Spray, Dark Blue Can be applied directly over firm, rusty surfaces For use on metal substrates For previously painted surfaces, apply hammerite rust cap enamel finish to a small area first to check adhesion and test for lifting or cracking Formulated for interior and exterior use Aluminum and galvanized surfaces require a prime coat of hammerite rust cap 48300 galvanized and aluminum primer