52213

Corrosion Resistant Coating for Automotive Suspension Parts  

May 22, 2009

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, TN, USA

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 Martex Paints Ltd    Birmingham, UK

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, SC, USA

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

Brian Terry
Aerospace - Yeovil, Somerset, UK

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
- San Diego, California

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