Cadmium growth - whiskers, crazing, or just corrosion
I recently pulled some conformal coated ECA assemblies out of a sealed bag that contained cadmium plated connectors and screws. Neither the connectors nor the screws were coated. The bag was stored in our stockroom for around 2 years at ambient temperature. The connector housing is completely covered with white straw like structures. This white "residue" comes off the housing just by blowing and/or touching with swab. The screws have white corral like growth covering them -this "corrosion/growth" is more difficult to remove. Under EDS analysis, Cadmium was identified on both. I am trying to find some information to help me identify if this Cd plating is "corrosion", "whiskers" and/or "crazing".
Any help would be greatly appreciated!Karen Achey
Process Engineer /electronics - Ocala, Florida
The condition Ms Achey has observed on her parts is "cadmium bloom", a condition resulting from the cadmium plating contacting an (usually a gas) organic acid source. We have seen it develop from exposure to acetic acid curing RTV rubbers and from formaldehyde glue in plywood shipping containers. I have also heard it can be produced from the formic acid given off by nearby ant colonies.
It will typically have an acrid odor, although I would caution against smelling it. The bloom is very toxic, highly frangible and is one of the reasons for the declining use of Cd in my company.
- Portsmouth, Rhode Island
October 15, 2009
What are the recommendations for the removal of cadmium formate?Roger J. Hartley
- Perkasie Pennsylvania
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