What Does
Cadmium Plating Mean?
Cadmium plating is a technique used to coat metal surfaces with a layer of cadmium. This technique provides excellent corrosion resistance and is commonly used in the aerospace, defense and electronics industries.
Corrosionpedia Explains Cadmium Plating
Cadmium plating is achieved using an electroplating process, wherein a metal surface is immersed in a solution containing cadmium ions. The metal surface is then connected to a power source's negative terminal, while a cadmium electrode is connected to its positive terminal. When an electric current is passed through the solution, cadmium ions are reduced at the metal surface, forming a layer of cadmium on the surface.
Cadmium is a soft white metal that acts as a "sacrificial coating" (a coating which corrodes before the substrate material) when plated onto steel, cast iron, malleable iron, copper, and powdered metal. To enhance the corrosion protection of cadmium plating, chromate conversion coatings can be applied over the plated metal.
Cadmium plating provides several advantages over other plating techniques, such as:
- It provides excellent corrosion resistance, even in harsh environments, such as saltwater and acidic environments.
- It has a low coefficient of friction, making it ideal for use in moving parts, such as gears and bearings.
- It is ductile and malleable, making it easy to form and shape.
- It provides an exceptional bonding surface for adhesives, such as those used in aircraft manufacturing, and is the preferred coating for saltwater environments.
- It has high conductivity.
- It has superior solderability.
- It can be favorably galvanically coupled with aluminum.
- It has excellent natural lubricity, which results in galling prevention and a low coefficient of friction.
- It produces less significant corrosion products than those of other plated coatings (such as zinc).
- It resists mold and bacteria growth.
The advantages of cadmium plating are especially useful in applications where components are repeatedly disassembled and reassembled, such as during scheduled maintenance of aircraft. Thus, cadmium plating is critical to the aerospace industry.
However, cadmium plating is also known to have several disadvantages. Chiefly, cadmium is a toxic metal; the plating process can release toxic fumes and waste products. Plus, exposure to cadmium can also lead to several health problems, such as lung damage, kidney damage and cancer. For these reasons, cadmium plating is subject to strict regulations in many countries.