Surface treatment systems are applied to aluminum die castings to provide a decorative finish, to form a protective barrier against environmental exposure, and to improve resistance to wear.
Decorative finishes can be applied to aluminum die castings through painting, powder coat finishing, polishing, epoxy finishing, and plating. Aluminum can be plated by applying an initial immersion zinc coating, followed by conventional copper-nickel-chromium plating procedure similar to that used for plating zinc metal/alloys.
Protection against environmental corrosion for aluminum die castings is achieved through painting, anodizing, chromating, and iridite coatings. Improved wear resistance can be achieved with aluminum die castings by hard anodizing. Where a part design does not allow the production of a pressure-tight die casting through control of porosity by gate and overfl ow die design, the location of ejector pins, and the reconfiguration of hard-to-cast features, impregnation of aluminum die castings can be used. Systems employing anaerobics and methacrylates are employed to produce sealed, pressure-tight castings with smooth surfaces.