Poor Galvanized Metal Adhesion: Paint that has lost its adhesion to a galvanized metal substrate.
Improper surface preparation, such as inadequate rust removal.
Failure to apply a primer before application of an oil-based or vinyl latex paint.
Failure to sand baked-on enamel finishes or glossy surfaces before painting.
Any rust on the metal should be removed with a wire brush; then, an acrylic latex corrosion-resistant primer should be applied (one coat is usually sufficient). New or previously painted galvanized metal that is completely rust-free can be painted with a top quality acrylic latex paint without applying a primer; however, a metal primer should always be applied to unpainted galvanized metal before applying an oil-based or vinyl latex top coat.