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-inhibitive primer should be applied (one coat is usually sufficient). Previously painted galvanized metal that is completely rust-free can be painted without applying a primer. A latex metal primer should be applied to unpainted galvanized metal, followed by a top quality exterior acrylic latex paint.