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Ted Mooney, P.E. RET
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for Metal Finishing 1989-2025
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Hydrogen Embrittlement Relief Ovens for Plating
Q. Does anyone have any insight on the use of direct fired gas ovens for embrittlement relief of zinc and nickel plated parts? I have been advised that direct fired gas ovens can, under some conditions, cause corrosion problems on the plated items during the bake cycle, anyone ever experienced this? The cycle is 400 F minimum for 4 hours minimum.
When compared to electric ovens and indirect gas fired ovens, the direct fired ovens win hands down on a cost analysis.
1996
A. I do baking in an electric oven. I recently explored converting to gas because of the enormous energy savings . I asked the advice of a customer who has been in the heat treating business for 40 years and he talked me out of it. He said they are harder to control and didn't like the firing packages required should you wish to automate. As far as corrosion I would only say that it is already known that flue gases are corrosive but to what extent do they contact the parts? If there is not a heat transfer mechanism--I'd be afraid to let the heated raw atmosphere contact plating.
Frank Zemo - Paterson, New JerseyQ. I'm a Materials, Processes, and Environmental Technologist at a military repair and overhaul facility. We have in house capability for a number of metal treatments, including Cadmium plating. My current problem is with our hydrogen embrittlement relief oven for cadmium plated parts. The oven currently in use is not vented. We run at a temperature of 375 ± 25 degrees F. As far as I can tell, the temperature is not high enough to vaporize the cadmium, sodium cyanide, or any other materials besides water that may be present as a result of the plating, but is there something I'm missing? Should our oven be vented?
Ryan AndersonIMP Aerospace - Halifax, N.S., Canada
A. I don't think cyanide has much to do with anything; presuming the parts have been well rinsed, the cyanide concentration is probably lower than some other things you might put in an oven at a similar temperature like lima beans, almonds, and apples.
Nor does it sound like the cadmium is an issue. According to the booklet 'Using Cadmium Safely--A Guide For The Workplace': "Fume is given off when the metal is heated above its melting point, as in welding". The melting point is about 321 °C, which is over 600 °F.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
A. Even lab ovens are vented to the lab. I have never seen a process oven that did not have a variable opening on the back or on the top.
If you mean power venting, I would say that it is not required. Any vent hole should probably be piped to the roof and possibly to the outside. It is a cheap fix if anyone is concerned. I have never heard of an oven operator having cadmium poisoning from the oven air/exhaust.
James Watts- Navarre, Florida
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