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Q&As since 1989


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I would like to understand if it is possible to chrome plate chrome-moly racing car suspension arms

2006

I am restoring a wonderful old Indy car. The fellow who is doing the work which requires real skill (I do the simple things!) has baulked at my desire to have the suspension wishbones and trailing/leading arms chrome plated so that the car looks fabulous. We would like to understand better the real theory behind post-plating heat treatment of mild steel tube , and if you can chrome plate chrome-moly tube and heat treat it to remove/substantially reduce the embrittlement problem.
60s and 70s open wheel racing cars often have suspension parts chrome plated and it would be nice to know what the rules really are about the practice. We are not even sure that the tube is chrome-moly , but the inside of the tube is beautifully smooth so is moly or drawn mild steel.
We would be most grateful for some information and enough advice so that we can make good decisions. Kind Regards , TIM KUCHEL

Timothy Rex Kuchel
Racing car enthusiast - Adelaide , South Australia

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2006

There may be two issues of concern, adhesion and hydrogen embrittlement.

It can difficult (but almost never impossible) to get good adhesion on some alloys because plating is done on active metal surfaces and some metals and alloys become passive almost instantly. I don't think 4130 chrome-moly is particularly difficult to chrome plate, but I haven't been involved with it, so you'll either have to wait for someone who has, or do a little research on the subject.

Plating processes and acid treatment processes release atomic hydrogen, and this will cause hydrogen embrittlement if the steel is hard. Although embrittlement relief does involve baking, it's actually a different subject than heat treatment because the temperature (375 - 400 °F) is below the temperatures required to affect heat treatment properties.

Pending study of the fine details, my first impression is that these parts can be nickel-chrome plated. Please see our FAQ about chrome plating if it confused you that I switched the subject from chrome plating to nickel-chrome plating. Good luck.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey