A variety of high quality surface finishes is another major advantage
Zinc die castings offer excellent plating characteristics. Electro-plating is generally a multi-layered coating consisting of one or two copper layers, one or two layers of nickel, and a final layer of chromium, brass, gold, or any other platable metal. Chromium plating is the most popular decorative finish when corrosion and high abrasion resistance are required.
Chrome plating adheres best to the ZAMAK alloys and ZA-8 followed by ZA-12. Chrome plating of ZA-27 is possible but more difficul due to the need to treat ZA-27 like an aluminum casting. Processes which provide a smooth, dense outer skin such as pressure die casting and permanent mold casting are preferred when plating is being considered.
Chomating is a low-cost chemical treatment that provides additional corrosion protection against « withe rust ». This form of zinc corrosion is caused by prolonged exposure to damp conditions. Chromate finishes are produced by simple dip methods which deposit a thin chromate coating. Chromate coatings are often applied to instrument, military and automotive components where low cost resistance to moisture is required. These coatings normally have a bronze tone or metallic lustre depending on the process used.
Phosphate coatings are primarily used to provide a good base for painting or powder coating.
A special zinc anodizing treatment is avaliable for zinc castings. This coating is completely different than that for aluminum alloys. Zinc anodizing is a functional coating providing maximum corrosion resistance in atmospheric and marine environments.
Since the process uniformly coats deep recesses and threaded areas, anodized zinc alloy casting can serve as an economical alternative when replacing traditional brass, bonze and stainless steel components.
Polishing and Brushing
Conventional high lustre polishing or brush finishing techniques can produce appearances similar to chrome plating or stainless steel. When lacquered, these finishes are suitable for decorative, interior applications.
All zinc alloys form an excellent base for paints. To aid paint adhesion, phosphate or chromate pretreatments are often employed. Zinc alloys can also be elctrostatically painted.
Powder coating involves electrostatic spraying of the zinc castings with an epoxy or polyester powder. The parts are then immediately oven cured for a hard dureble finish. The result is an even, inexpensive, corrosion resistant plastic coating. Powder coatings are avaliable in a wide range of colours.
Source : Interzinc