Discoloration from Hydrogen Embrittlement Relief after Plating
A discussion started in 2011 & continuing through 2017 . . .February 23, 2011
Q. We have been cadmium plating steel parts of Landing Gear components. Recently we have acquired a new oven for de-embrittlement relief.
However after 23 hours at 375 °F baking the parts show local and severe discoloration as seen on the photos.
If you can guide us about the possible reasons or a way to identify root cause,we would be grateful.
Note: The issue has not been observed with the "old" oven, which suggests the problem is about the "new" oven.
Plating Shop Employee - Istanbul, TURKEY
February 28, 2011
I would start by putting 5 or 6 thermocouples in various spots inside the oven. You may be experiencing localized hot spots and this method will tell you.
March 1, 2011
A. Since it is an aircraft part, the new oven was supposed to have an oven temperature survey done before it was used.
- Navarre, Florida
March 2, 2011
A. Hi Ozgur,
aerospace - Yeovil, Somerset, United Kingdom
A. We de-embrittle tubes after cadmium plating, they often have similar staining, our specs allow us to dip the components in 0.1%v/v sulphuric acid for a few seconds.
This does get rid of the staining and reactivate the cadmium surface for dichromate passivation.
Hope this helps.
- Isle of Man, Great Britain
March 7, 2011
Q. Our specs also favors a reactivation agent such as sulphuric acid or sodium cyanide.
However we are not sure how serious the stains could be and try to avoid extra work (cause the "old" oven with ventilating duct do not have such complications).
As a summary,
- We have closed the flap of the "old" oven and finally observed similar discoloration, which strongly suggests the case could be about air quality/ventilation.
- For the local hot spots, I will use 3M temperature recorder tapes on the parts. (Thermocouple do not seem practical and cheap :))
I will inform once the "experiments" are finished.
Please inform if you will have additional comments/advices.
- Istanbul, Turkey
De-embrittlement, alkaline zincMarch 19, 2017 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread
Q. I am struggling to get a good aesthetic finish on zinc plated high-tensile parts. They look good after zinc plating, but after de-embrittlement (8 hrs at 200 °C) they come out of the oven blotchy.
I then colour passivate them but the blotches are still visible.
The zinc is not coming off and the problem is just a cosmetic one, but the customer is not happy.
How can this be rectified?
March 20, 2017
A. Hi Daniel,
Aerospace - Yeovil, Somerset, UK
March 20, 2017
A. Hi Daniel,
- Cold rock in the Irish Sea
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