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Hydrogen embrittlement in zinc-cobalt plating on SPROCKET (MATERIAL SAE 8620)

I WANT TO KNOW DUIRNG ZINC-COBALT PLATING PROCESS, HYDROGEN EMBRITTLEMENT WILL DEVELOP OR NOT. IF SO recommend THE CORRECTIVE PROCESS.

Senthil
LGB - Caoimbature, Tamilnadu, India
2005

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Generally speaking, any plating process will cause HE. Some are much worse than others. I found that over etching (any thing more than the minimum required) was a far greater source of HE. Do a search of the site as there are dozens of letters about it. Proper design reduces the bad effect (not the amount of HE) generous radius is the easiest and cheapest help. To reduce the amount of HE, get it into the post plate bake cycle as soon as possible after the plate. It goes deeper with time and is nearly impossible to remove. The length of time and the temperature of the bake will depend on the hardness of that particular alloy. Too high and you will start to temper the alloy which you may not want and possibly can not stand. Another help might possibly be to use the lowest Rc that will provide the results that you need.
Measuring HE is a very difficult and costly process. Nearly everyone avoids testing by limiting the amount of HE as it is the most effective way to build a part.

James Watts
- Navarre, Florida
2005