Hydrogen embrittlement and knives

J

Jcdelamater

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Oct 5, 2022
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I've been wondering recently why we as knife makers don't seem to worry about hydrogen embrittlement when etching our knives. I know from my engineering experience that soaking steels in acid is a great way to let the H+ ions into the crystal structure, but we all seem quite happy to do this when etching. Does anyone know why we don't seem to worry about this in knives?
 
Jcdelamater said:
I've been wondering recently why we as knife makers don't seem to worry about hydrogen embrittlement when etching our knives. I know from my engineering experience that soaking steels in acid is a great way to let the H+ ions into the crystal structure, but we all seem quite happy to do this when etching. Does anyone know why we don't seem to worry about this in knives?
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How much deep H+ ions can get into steel ? Most time etch time is short . . .
 
Stainless damascus will etch in HCL

most others will use a diluted and weak acid like Ferric chloride or
FeCl 3(H2O)x
no free H+ in that.


vinegar



You could just re temper if you think it's a problem.
 
There's an article out on the net called "The Chemistry of Ferric Chloride" and it's on artmondo dot net. Wish I could link it direct. :-(
It explains what happens when you dissolve ferric chloride (FeCl3) in water and why it's so acidic.
 
We don't worry about hydrogen embrittlement anymore than we worry about tempered martensite embrittlement. The reason is it doesn't apply to knifemaking.

Welders worry about it in some cases, but even they don't pay it much attention past keeping the rods dry.
 
1. Metals we typically use aren't AS susceptible to embrittlement.
2. The temperatures of our metals and ferric chloride don't lend themselves to hydrogen absorption
3. Based on the history of this area on forums I'd say we've had amble time for it to prove itself a concern. Both from a useage concern or from metallurgical analysis.
4 if it was a concern a tempering/heating cycle to 100c afterwards would diffuse/ break any hydrogen bonds of concern. Least ways that the way the parts company fix that problem
 
I’ve heard reports of it being a problem on the edge of an etched knife. The edges won’t form cleanly or they just crumble when used. It’s just a few stories from knives that were already sharpened ie thin sections. After a couple sharpenings the problem went away.
 
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