I have a 15 gallon galvanized metal container out back with some parts from my south bend 13 soaking in lye. I looked up after I had put the parts in if it would attack zinc. Apparently it does and it produces hydrogen. There's some bubbles coming up around the part which I assume is hydrogen from the zinc being eaten off my container. Should I be worried about hydrogen embrittlement?
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Hydrogen embrittlement
- Thread starter Dog250
- Start date
- Replies 5
- Views 1,797
Milland
Diamond
- Joined
- Jul 6, 2006
- Location
- Hillsboro, New Hampshire
HE is usually more an issue when plating higher strength (>180Ksi or so) steels, with the cast iron parts you're dealing with it's likely not a big deal. And I suspect as it's the container, not the parts generating the gas that makes it less of a problem.
Milland
Diamond
- Joined
- Jul 6, 2006
- Location
- Hillsboro, New Hampshire
Check out this URL: What is Hydrogen Embrittlement? – Metal Finishings Ltd and you'll see that maybe there's a little more of an issue with cast iron than I thought, due to inherent brittleness. Frankly, I still doubt that for your purposes the parts are at risk, but yeah, next time use a plastic or stainless bucket.
If you think you're going to have a HE problem - bake at 400F to allow the hydrogen to diffuse out of the parts. Bake time varies with strength level. Higher strength/hardness = longer bake. Times 8 to 20 hours depending on the strength level. There's a table in this article: www.heat-treat-doctor.com/documents/hydrogen embrittlement.pdf
Milland
Diamond
- Joined
- Jul 6, 2006
- Location
- Hillsboro, New Hampshire
A good point raised in the article I linked to in #4 is that time is critical when dealing with bake-out, you want to do it as soon as possible to ensure removal of the hydrogen. Simply baking well after the potential generation may leave too much H in place regardless of bake-out duration or temp. Note that even complete heat treating processing will not necessarily remove remnant H.
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