Pure cadmium plating to ASTM B766
The cadmium deposited coating on bolt has a low coefficient of friction that can reduce the tightening torque required and allows repetitive dismantling.
The cadmium coatings is provided in various thickness up to and including 25m from pure 99.99% cadmium either as electrodeposited or with supplementary finishes. The prime purpose of the supplementary chromate finishes on the eledtrocleposited cadmium is to increase corrosion resistance exposed to various environmental conditions.
BBN cadmium-coated products salt-fog spray tested to 720 hours has proven without a spot of rust. This initiates that cadmium electrodeposited coating has 'much better corrosion resistance' than zinc plating or hot-dip galvanizing. Corrosion products formed on cadmium is tightly adherent, and unlike zinc, cadmium does not build up voluminous corrosion products on the surface, which allows for proper functioning during corrosive exposure of moving threaded assemblies.
People are often confused to differentiate the coating finishes because the colors appear very similar. Use of a proper specification to secure the interests of getting real cadmium, with the keywords 'Cadmium, electrodeposited coatings to ASTM B766', or with any suglementary finishes type II or III, and ask for the 'Letter of Conformity'.
Electrodeposited cadmium coatings shall be identified by types and on the basis of supplementary treatment required as follows :
|I||None, as deposited|
|II||With colored chromate treatment|
|III||With colorless chromate treatment|