A
variety of high quality surface finishes is another major advantage.
Electro-Plating
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 palatable 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
difficult due to the need to threat ZA-27 like an aluminum casting. Processes
that provide a smooth, dense outer skin such as pressure die-casting and
permanent mold casting are preferred when plating is being considered.
Chromates
Chromating
is a low-cost chemical treatment that provides additional corrosion protection
against "white 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 require. These coatings normally have a bronze tone
or metallic luster depending on the process used.
Phosphates
Phosphate
coatings are primarily used to provide a good base for painting or powder
coating.
Anodizing
A
special zinc anodizing treatment is available 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 castings can serve as an economical alternative when replacing
traditional brass, bronze and stainless steel components.
Polishing
and Brushing
Conventional
high luster 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.
Painting
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
electrostatically painted.
Powder
Coatings
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 durable
finish. The result is an even, inexpensive, corrosion resistant plastic
coating. Powder coatings are available in a wide range of colors.