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Corrosion Resistant Coating for Automotive Suspension Parts

I am a design engineer who's plating and metallurgic knowledge is admittedly weak. I designed some aftermarket automotive suspension parts for a customer who needs help in specifying a suitable plating or coating. The parts are 4140 steel and need to be Rockwell C22. He wants a 'thinner' plating like cadmium rather than zinc but he's not sure if that's the best and will it interfere with the hardness, cause any hydrogen embrittlement issues, etc. These will be fairly low volume parts sold to enthusiasts, not mass quantity stuff sold at the local auto parts store. Reading some of your posts you seem to have the in-depth knowledge that we don't and any help you can offer would be appreciated!

Matthew Humphreys
Designer - Maryville, Tennessee, USA
May 22, 2009

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First of three simultaneous responses --

I would suggest you evaluate zinc phosphate pretreatment followed by powder coating. The choice of colours could include red, yellow, blue plus many more to entice the enthusiast motorist.

Terry Hickling
Birmingham, United Kingdom
May 26, 2009

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Second of three simultaneous responses -- May 26, 2009

Zinc electroplating is no thicker than cadmium, provides equal corrosion resistance, and is more readily available and costs less.

Three ten-thousandths inch of zinc with yellow chromate conversion coating will last a long time, outlasting much of the rest of the car. There should be no problems with hardness or hydrogen embrittlement.

Jeffrey Holmes, CEF
Spartanburg, South Carolina

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Third of three simultaneous responses --

Are you still allowed to use cadmium in non-aerospace applications in the USA? Wow...

Brian Terry
Aerospace - Yeovil, Somerset, UK
May 27, 2009

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May 27, 2009

The US military is phasing out cadmium plating for environmental reasons, replacing it with vapor or sputter deposited aluminum. There is also a wet-plating of aluminum available. I don't think zinc works as well as cadmium; it is certainly not considered a suitable replacement for military applications.

A number of companies offer IVD aluminum plating. You should easily find them on the web. The wet aluminum plating process is patented, so only one company offers that service.

Jim Treglio - scwineryreview.com
PVD Consultant & Wine Lover - San Diego,
California

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Hi

Only to avoid corrosion during material storage you can try some lacquer or dry type rust preventive oils which is easily available. Or try to do mechanical zinc plating In which you will not face any hydrogen embrittlement issues.

Vijendran Sudeendran
- Chennai, India
June 4, 2009