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Cadmium Plating Alternatives
|Common Applications||Versions of Cd Plate||Specifications|
Cd is a heavy metal cumulative poison and a probable (Class B1) carcinogen. Cd plating chemistry involves the use of several toxins. Cd is deposited from a cyanide bath and post-treated with chromate sealant. Cd, chromate, and cyanides are all heavily regulated because of their toxicity. Cd regulations:
- EPA: Limit 5ppb in drinking water
- OSHA: Cd PEL is currently 0.1mgm-3 for fumes, 0.2mgm-3 for dust
- European rules (ELV, WEEE, RoHS): 0.01wt% limit in electrical and electronic products and vehicles
- European REACH: Cd plate not permitted on many products, including vehicles; except aircraft, electrical contacts, and critical safety equipment
- Requires chromate passivation (European REACH and RoHS restrictions)
Personnel may be exposed during manufacture, depot overhaul, and operational level touch-up and repair.
- OEM and depot personnel may be exposed to Cd and As in liquids and mists used in plating and to Cr6+ in chromating processes. Emission controls, PPE required.
- Maintainers are exposed in corrosion control and localized touch-up (brush Cd). PPE required.
- Cd can be leached during washdown of systems containing Cd-plated components (e.g., engines), producing hazardous waste
Alternatives, Applications, Status
Various alternatives are in production for different military and commercial applications. All of these alternatives are commercially available with the exception of the LHE ZnNi, for which the chemistry is available, but not the supply chain. However, LHE ZnNi is looking like the closest to a drop-in replacement, except for electrical connectors, where the material does not pass conductivity testing unless it is chromate passivated.
|Most Common Cd Alternatives||Examples of Authorizations and Implementations||Specifications|
|Corrosion-resistant (CRES) materials – stainless steels, Ti, composites||Engine components, fasteners, connectors||Various|
|IVD Al (Ivadizing), pure evaporated Al||Used by OEMs and several depots||MIL-DTL-83488B|
|Electroplated Al (AlumiPlate)||F-22, F-35 landing gear and other structural components, connectors||MIL-DTL-83488B|
|Arc or flame sprayed Al||Bombardier Dash 8||MIL-DTL-83488B|
|Metallic-ceramic coatings (e.g., SermeTel and equivalents), non-embrittling formulations||Initially used on F-22 landing gear||MIL-C-81751C|
|Zn- and Al-filled spray and dip-spin paints and ceramics||Commercial automotive fasteners||Numerous automobile manufacturers|
|Acid ZnNi||Suitable only for low strength alloys (<160ksi) as embrittles. Permitted for electrical connectors||
MIL-DTL-38999 and other connector specs
|LHE alkaline Zn(14-16%)Ni||Qualified by Hill AFB for landing gear. Best results with trivalent passivation. Permitted for electrical connectors – must be chromate passivated||Local Hill AFB spec. Commercial specs under development. MIL-DTL-38999 and other connector specs permit ZnNi|
|Electroless Ni-PTFE (electrical connectors only)||Permitted for electrical connectors. Galvanically dissimilar to Cd||MIL-DTL-38999 and other connector specs|