Electroplated zinc protects steel, cast iron, malleable iron, copper, and brass from destructive corrosion. The zinc chemically bonds to the part surface and functions as a "sacrificial coating", corroding before the base material but in the process greatly extending part life. Zinc is an efficient, economical coating, with a minimal environmental impact. Plated zinc is not recommended for equipment that is continually immersed in solutions, petroleum applications, pharmaceutical applications, or food-handling applications.
RACK AND BARREL ZINC PLATING
Plating methods for applying zinc coatings include the use of rack and barrel plating processes. With rack plating, the parts are affixed to a jig during plating to hold them in place and prevent damage. Barrel zinc plating involves placing the parts inside a specially designed vessel containing the plating bath. The barrel is rotated slowly during the plating process to coat the parts.
Rack zinc plating is normally the best choice for smaller, delicate parts that cannot withstand the tumbling caused by a rotating barrel. Barrel zinc plating, on the other hand, is typically more cost effective and less labor intensive. It’s often the better option for plating many parts at once.
FEATURES AND BENEFITS
- High efficiency and greater plating speed
- High gloss coatings with superior coverage
- Decorative appearance resembling chrome
- Comparatively low plating cost
- Boric acid-free processes available
- High temperature stability
The various types of zinc plating can be identified by the color produced by the different formulations. Each color offers different levels of corrosion protection:
- Yellow Zinc — This type of zinc coating is commonly used in the automotive industry and offers an average level of protection against corrosion .
- Black Zinc — Black zinc coatings are available as a black oxide that can actually be olive-drab in color, or as a pure black coating. The former will normally provide slightly better corrosion resistance.
- Clear or Blue Zinc — This coating formulation tends to offer fewer amounts of corrosion protection, although it’s regarded as being more environmentally friendly.
- Acid Zinc — Acid zinc plating differs from other types of zinc plating, as it does not introduce cyanide into the plating bath. A key advantage of acid zinc is that it can be effective for use on hard-to-plate substrates.