The surface to be painted must be clean and free of dirt, grease, oil, rust, mill scale, loose or peeling paint and other surface contaminants. Remove rust or mill scale by sanding and/or hand tool cleaning. Old glossy enamel finishes must be sanded to a dull finish, dusted, and then primed with the appropriate primer.
Always prime new or bare ferrous metal with a corrosion resistant primer. A phenolic lift proof primer must be used as a primer for high performance coatings such as two package epoxies and polyurethanes.