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Bake temperature / time of Zn/Fe plated automotive type compression springs

2006

We are having compression spring manufactured and having a Zn/Fe trivalent chromate coating + sealer added. These parts are used in automotive latching systems. The plater bakes the parts after initial zinc/iron plating to eliminate any hydrogen embrittlement that may have developed and adds trivalent + sealer after. I believe this is the correct process.
My questions is what is the preferred temperature/time for stress relieving the spring during production and the temperature/time used to bake the part to eliminate hydrogen embrittlement.

Regards,

Robert Hoel
Intier Closures - Toronto, Canada

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2006

Hydrogen embrittlement has been a subject of many letters over the years. Search the site for many opinions.
There are basically two secrets to avoiding hydrogen embrittlement problems. 1. keep the etch time to the absolute minimum to do the job. 2. get the parts into the bake oven as soon as possible after the last rinse.
Now, it is a time temperature tradeoff. If you go too high, you affect the hardness and the resulting changes in properties. The cost is a long bake time. 375 F for anywhere from 4 hours to 24 hours might be required to pass qc tests. This is only 1 of many options.

James Watts
- Navarre, Florida