The best way to get paint to stick to chrome, aluminum, galvanized, and other "hard to stick surfaces", is to use a self etching primer. Most self etching primers consist of 2 parts.... the primer and the activator(acid). When mixed they will produce an acid etching primer that will stick to damn near anything. Vera-Prime is one such primer made by Dupont. Spies-Hecker, PPG, BASF, and other paint companies make it also. I've used it on glass, wheels, car amps, interiors, even a tail section of a hospital helecopter.