Masterchem Industries 41140 Spray Paint, Black 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