springs and bolts in acid - hydrogen

Saw this post and thought - why not ask the experienced pragmatic folk?


Working with weldable structural steels, I was once totally disbelieving of how susceptible bolts and some hardened steels are to hydrogen and the effect of acid pickling.
Millions of times more susceptible...
How many of you have been involved in sorting out delayed cold-cracking breaking of bolts and studs?
Rich
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"Richard Smith" wrote in message
Saw this post and thought - why not ask the experienced pragmatic folk?

Working with weldable structural steels, I was once totally disbelieving of how susceptible bolts and some hardened steels are to hydrogen and the effect of acid pickling.
Millions of times more susceptible...
How many of you have been involved in sorting out delayed cold-cracking breaking of bolts and studs?
Rich
==================================================https://en.wikipedia.org/wiki/Intergranular_corrosion
I vaguely remember from a college Materials Science class that alloy steels can also suffer from fractionation during solidification that results in differing compositions in adjacent crystals, which then have different attractions for electrons and thus form microscopic batteries. All they need to self-discharge is a conductive liquid electrolyte that allows migration of oxidized ions.
Of course being a college student in the late 60's was in itself conducive to brain cellular corrosion. I realized that I could satisfy the usually onerous liberal arts course requirements by taking theatre classes that were way more fun (and unflunkable) than the standard offerings. To my surprise I and my techie friends participated in class discussions more than the wannabe actors did. Perhaps we were immune to or at least less terrified of the caustic wit of the professors/directors.
La Vie Boheme came along for free.
https://www.youtube.com/watch?v=xTvhS5d1kn8
https://www.metrolyrics.com/la-vie-boheme-lyrics-rent.html
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wrote:

I decided to clean up a couple mildly rusted bicycle chains with a "rust remover" Put the chain on the bike, jumped on and promptly snapped the chain. Repeated 3 times untill all 3 chains were broken, then went and bought a new chain. About 6 years ago - still on that chain.
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Interesting. When doing research on hydrogen in welds / steels, it was absolutely not possible to get any hydrogen into structural steels by immersing them in acid. Made a drilled "bobbin" for extra surface area and less thickness from surface, visisble hydrogen evolution reaction at the surface - but in a "Leco" analyser (thanks Esab) - no measurable hydrogen. One of reasons I needed to be corrected that highly hardenable steels - notably for bolts and high-strength tie-bar "studs" - can be very susceptible. Regards,
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