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Hydrogen Embrittlement after hard chrome finish


tk2

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I've seen a couple of STI frames develope cracks after hard chroming and have read that Hydrogen Embritlement occurs to steel after receiving a hard chrome finish. The plater I talked to said they bake all parts after plating to relieve the hydrogen embrittlemt, but it still seemed like parts failure was a concern after plating.

So my question is, does hard chrome finish weaken the gun parts and lead to premature failure?

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I don't have scientific facts to back this answer up but....no. At least nothing you would notice. I have seen, owned, and used several hard chrome guns and I have never noticed a difference in failure rate due to hard chrome.

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well, Tim, it looks like I will be off to google or wikipedia here in a minute to look up "hydrogen embrittlement".

My first knee jerk reaction is to be skeptical.

Do you have any pics of where these cracks are?

I only ask that because...well... I have seen some questionable milling practices with respect to slides and frames, totally ignoring some common engineering mechanics/metallurgy principles...or at least I think so...

again, that's my first knee jerk reaction. I probably am wrong, so YMMV.

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'..Hydrogen Embrittlement: Hydrogen embrittlement can occur when hardened tool steel (Rc 52 or harder) is plated with industrial hard chrome. Stresses caused by the formation of hydrogen in the deposit can render the component susceptible to fracture. Although overlooked by many platers, this problem is easily solved by baking the component at 350 F within 8 hours of plating...'

http://www.meadvilleplating.com/chrome.html

"...Provided that high strength steels are stress-relieved before plating and heat-treated again afterwards (usually for 3 to 12 hours at about 375*F), there will be few problems with hydrogen embrittlement..."

http://www.dynachrome.com/hard-chrome.html

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Years ago I had a long discussion with Ron Mahovsky at Metalife on the subject of hydrogen embrittlement. His opinion - and this is a guy who's plated gun parts for decades - is that the only way hydrogen embrittlement can become a problem is (1) if there's an underlying flaw in the part itself, then the plating can exacerbate that and lead to cracking, (2) the plating process is repeated again and again. The customer says, "I want the gun plated," then they say, "I've got to have a beavertail," so the gun gets stripped and replated after that. Then of course then have to have a mag funnel installed.... And so on. That's why most platers will tell you, "Get the gun exactly the way you want it before hard chroming, because I'm only going to do this once."

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So I guess the short answer to your question would be, "No, if you're plating quality parts, and you're only doing the gun one time, it is HIGHLY unlikely the plating process will lead to cracked parts."

I would agree with Duane... I've discussed this with Virgil Tripp and although he said it seemed to happen more years ago it's not really something to worry about with the hard chrome processes today. I've also discussed this with the SVI guys and decided to hard chrome 2 different SVI guns so we'll see if there ever becomes an issue. I highly doubt it.

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Hard chroming is generally prohibited in the aircraft/parachute hardware manufacturing industry precisely because of hydrogen embrittlement. You certainly wouldn't want a piece of life-support hardware failing during load or after extensive vibration.

Put it on a hobby gun and generally all you risk is a cracked frame or slide.

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  • 2 weeks later...

I do not have experience in chroming, but I know about steelmaking. In making steel, hydrogen embrittlement usually occurs because they get water into the refining ladle and it gets so hot it dissassociates into hydrogen and oxygen. It does not take much (8-10 parts per million) to cause an issue.

That said, I do not see how the hydrogen would form (low temps) and how it would be able to penetrate into the metal of the gun (at relatively low temps) and be able to cause embrittlement upon hard chroming. It sounds more like a cover for other flaws in the metal. (say something like acid leaching of non-dispersed alloying metals by the bath or underlying microcracks in the weapon)

Edited by bubbadoc
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