The Corrosion Protection Benefits of Electrodeposited Cadmium Plating
Cadmium-plated aluminum is a true workhorse for military and highly demanding industrial applications. With its excellent corrosion resistance and other technical advantages, cadmium generally acts as a “sacrificial coating” over a suitable underplate, such as electroless nickel underplating.
Benefits of Cadmium Plating
Cadmium itself is a soft, tin-like white metal that is not a strong plate on its own. Its resistance to wear and abrasion is far less than a nickel plate, so it’s not a barrier-layer coating. However, it has many desirable properties that make it ideal as a sacrificial overcoat to a strong underplate or base metal.
- Low material cost — Cadmium is an inexpensive plate compared to many other options
- Very malleable/ductile — A suitable trait for crimped components and the like
- Corrosion resistant — An excellent top coating designed to corrode slowly, protecting the underplate and base metal
- Galvanic compatibility with aluminum — Ideal for aerospace applications
- Saltwater protection — Cad is highly popular for corrosion protection in saltwater and salt spray environments
- Resists mold and bacteria growth — Excellent for environments where moisture is a concern
- Highly conductive — Useful in applications that demand low electrical resistance
- Natural lubricity — Lending anti-galling and low-friction properties; eliminates stick-slip under torquing (plated threads)
- Cosmetic advantages — Easily dyed and suitable as either a final finish or a base for paint
- High-adhesion surface — When adhesives are needed, cadmium offers an exceptional bonding surface
- Superior solderability — When joints are needed in addition to protection
Cadmium coatings can be further enhanced when applied as chromate conversion coatings. As plated, cadmium is silvery. A chromic acid passivation bath creates a chromate topcoat that lends cadmium its more familiar gold hue, but other color options are available. For military and defense applications, olive drab is a very popular chromate conversion. Even clear chromate is possible, eliminating the typical yellow/gold color in favor of a somewhat matte appearance that is metallic but without the high gloss of nickel. In any case, a chromate topcoat in the cad plating process enhances corrosion protection.
The Electroless Nickel Underplate
Aerospace and aircraft aluminum is frequently plated first with electroless nickel to improve wear resistance and add adequate corrosion resistance while retaining great conductivity. These traits make electroless nickel an ideal plate for locations such as electrical connectors, exoatmospheric equipment, avionics box accessories, and missiles.
However, once corrosive atmospheres become a primary concern — such as salt spray exposure in marine environments — electroless nickel’s benefits can be expanded with the additional support of a cadmium coating.
1,000 Hours of Salt Spray Protection
There’s a reason that cadmium is a favored coating in saltwater applications. Cadmium (with chromate treatment) over electroless nickel plating will maximize the corrosion resistance and improve the saltwater protection to impressive levels. With sufficient thickness in each layer, this combination can easily achieve 1,000 hours of salt spray protection.
Today, cadmium coating with a chromate treatment over electroless nickel is a staple finish for aircraft parts and repair. Cadmium plating is relied upon for demanding or corrosive industrial conditions in the aerospace, military, mining, automotive, and aviation industries on a wide range of parts, from fasteners to chassis to connectors and electrical components.
Specialized Monitoring & Environmental Stewardship
Environmental directives over the last decade have continued to evolve cadmium plating processes, which involve toxicity that must be mitigated. Specialized monitoring is required, above and beyond those for electroless nickel plating.
Metal Finishing Technologies takes its role as an environmental steward seriously. MFT’s FAA Repair Station has been certificated since 1991 and is certificated to apply electrodeposited cadmium and low stress, ductile nickel, and electroless nickel onto worn components for the purpose of restoring them to dimensional tolerances. We are able to satisfy multiple relevant specifications, including QQ-P-416, MIL-STD 865, and ASTM B766.
Our customers trust the sustainability and green nature of our cadmium plating services. Get in touch today for more information or to request a quote!