Cadmium


Cadmium is used for providing sacrificial (cathodic) protection to steel. Cadmium’s lubricity and ability to prevent galling between sliding surfaces is a key property for many of its applications. In marine environments, cadmium outlasts equal thicknesses of zinc. It is also readily solderable with nonacid fluxes, has good electrical conductivity and, when corroded, forms thinner and less harmful corrosion products than zinc does. For installing fasteners, a predictable high tension is obtained at low torque with cadmium. This feature, combined with its compatibility with aluminum, has made cadmium a popular finish for aerospace fasteners and other military applications. Below is the most common specification for cadmium plating.

ASTM B766

Type I – As-plated without treatment

Type II – With colored chromate treatment

Type III – With colorless chromate treatment

Class Fe/Cd 5 – Service Condition 1 – 5 um (.0002”) Thick

Class Fe/Cd 8 – Service Condition 2 – 8 um (.0003”) Thick

Class Fe/Cd 12 – Service Condition 3 – 12 um (.0005”) Thick

Class Fe/Cd 25 – Service Condition 4 – 25 um (.001”) Thick

For information on eliminating hydrogen embrittlement per ASTM B766, click here