Cadmium plating is a type of coating process that offers technical benefits such as outstanding corrosion resistance, even in high-salt and low-thickness environments. Cadmium is the byproduct of the production of zinc, and it was only in 1920s that cadmium plating was recognized as a form of protective coating.
Cadmium plating is also known as cad plating.
Electroplated cadmium is a robust and versatile metallic coating. Cadmium is a soft white metal that, when plated onto steel, cast iron, malleable iron, copper, and powdered metal, functions as a "sacrificial coating," corroding before the substrate material. To enhance the corrosion protection of cadmium plating, chromate conversion coatings can be applied over the plated metal, yielding the familiar gold color as seen in the above picture. Other colors, such as olive drab are also available.
Cadmium plating offers an exceptional bonding surface for adhesives, such as those increasingly used in aircraft manufacturing, and is the preferred coating for salt-water environments. Additional advantages of cadmium plating include: low electrical resistance; outstanding conductivity; superior solderability; favorable galvanic coupling with aluminum; and excellent natural lubricity, which results in prevention of galling and a low coefficient of friction. Furthermore, the corrosion products of cadmium are less significant that those of other plated coatings such as zinc. These characteristics are especially useful in applications where components will be repeatedly disassembled and reassembled, such as in scheduled maintenance of aircraft. Thus cadmium plating continues to be critical to the aerospace industry . Cadmium plated surfaces resist mold or bacteria growth.
In some limited applications, zinc nickel, alloy plating may be an acceptable alternative to cadmium plating. Please contact Chem Processing for more information about this substitution.
Cadmium plating is not recommended for spaceflight applications due to its propensity to sublimate, outgas and spontaneously form whiskers in a vacuum.