Electronic – Health hazard of cadmium plated connectors

4th year chemistry student here. I have experience with dangerous chemicals, regulations and best practices as I am exposed to them on a weekly basis. Moreover I have studied and formulated my years winning zinc corrosion protection paint blend for Hempel Incorporate.

I've noticed that the green coating is gradually worn out.

• This is definitely not good, 'olive drab' is a chromate finishing. This type of chromium is hexavalent and is very carcinogenic, genotoxic in fact. You are not working in the most exposed industry with regard to this health risk, but still, you wouldn't want 'olive drab' hands to come into contact with your mouth,eyes or nose, especially on a daily basis.

-https://www.cdc.gov/niosh/topics/hexchrom/

-https://en.wikipedia.org/wiki/Hexavalent_chromium#Toxicity

-https://www.finishing.com/110/07.shtml

-https://www.serdp-estcp.org/asetsdefense/Clean-Alternative-Information/Cadmium-Plating-Alternatives

Is it in a safe compound when plated on nickel? I read "cadmium plated nickel base" as a cadmium layer on top of nickel. So it is no compound, right?

• It is plated and with repeated use/handling the cadmium layer could potentially rub off on hands and if those hands are not cleaned before interacting with the respective mouth, nose, eyes, etc., then one could consider it unsafe. Moreover I would not say its safe relative to other coatings.
• Correct, it is not a compound ( bonded at the atomic level), more a lamination and thus more likely to "rub-off" as the resulting bond isn't the strongest .

https://en.wikipedia.org/wiki/Electroplating

How does cadmium behave when touched with bare skin? Is it somehow solved by acids / fat / other stuff?

• Hand sweat consists mostly of water and trace amounts of urea, minerals and lactic acid. I would say that lactic acid is a moderate acid with a pka of approx. 3.5, but we are talking trace amounts in sweat. So cadmium doesn't really react with 'hand chemicals'. But after repeated handling this will likely be a different case, in conjunction with the above mentioned mechanical "rub-off". Watch out for exposure to stronger acids, especially if those connectors are in a oxygen scarce/vacuum environments.

https://en.wikipedia.org/wiki/Perspiration

In conclusion, these coatings becomes a real health risk when they enter the body, especially if inhaled, which is not the case here. They could however come into contact with eyes, nose, mouth,etc. through hand contact so be very wary of this. The olive drab rub-off is alarming. So in answer to your main question, I would say no - it is not generally safe.

The use of cadmium plating is understandable; it provides great sacrificial plating for corrosion protection, great conductivity (for grounding, emi shielding etc.), it can operate at aerospace temperatures, great lubricity, and excels with regard to other connector performance requirements - all at a great price point.

Initially I was wondering why zinc plating wasn't used but reasoned that this was due to aerospace requirements prioritizing the above-mentioned properties. However, I just read that Boeing already found a zinc plated alternative some 30 years ago (1992). Moreover it seems that the EU, SAE (society of Automotive Engineers), Raytheon and other agencies have found alternatives and are moving away from cadmium plated hardware. SAE state that Electroless Nickel Teflon is closest alternative. See the following links for more alternatives.

https://apps.dtic.mil/dtic/tr/fulltext/u2/a602494.pdf

https://www.turi.org/content/download/9287/16338/file/Alternatives%20to%20Cadmium.Misiaszek.Aerospace%20Defense%20Conference.24%20September%202013.pdf

https://dev.caltechplating.com/nickel-cadmium-diffused/