Letter 32012

Alternative to Cd plating  

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EOU has put restrictions on usage of CADMIUM as corrosion-protecting material; under the RoHS guidelines. Hexavalent chrome is also similarly under the "banned-item-list".

Any research / Development in finding a viable substitute for CADMIUM plating and that too WITHOUT hexavalent CHROMIUM ?

Expected solution should meet 500 hrs salt spray test, be conductive, and without changing the mechanical size of the components in uncontrolled manner.

Info sharing / brain-storming is most welcome!

Pramod Bapat
Amphenol Interconnect India Pvt. Ltd. - PUNE, Maharashtra, INDIA

You have asked THE question of the moment, if you find the "Holy Grail" please let the whole of the Aerospace industry know, we are waiting with baited breath for the drop in replacement for cadmium, especially without hexavalent chromium involved. There is plenty of literature out there on all sorts of viable alternatives, none of which seem to be the ideal answer, but each with their own merits and drawbacks.

You could look at zinc alloy plating, this has been used successfully in certain circumstances, there are plenty of alloy choices out there as well, such as zinc/nickel, zinc/tin or zinc/cobalt. How about IVD aluminium? Nickel/PTFE is another possibility.

I think you need to define exactly what the coating needs to do and what properties (other than corrosion resistance)you want and then trawl through the many products available on the market and (I'm afraid there is no easy way around this part) test the product that may be suitable, and see if it does the job.

Brian Terry
Westland Helicopters Ltd - Yeovil, Somerset, UK

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