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vinegar soak solid black.."foam"..?


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I couldn't figure out where exactly to place this...

Has anyone seen this before?  I've never heard of or seen this type of build up....

Hammer vinegar soak.jpg   Hammer vinegar soak3.jpg

 

It was some lightly used white Vinegar, and what I was told was just cold-rolled mild steel that I was trying to make my first hammer out of.
I thought a good vinegar soak would be good, but I may have forgotten about it for a day...or 14....and we had a heat spike here in the middle of that time (highest temp was 109 outside. I'm Oregonian, 80 is too high for me:P).

The build-up was solid, didn't dissolve in hand, but I could remove it with my fingers, and after you remove it it has a nice mustardy rust underneath
Hammer vinegar soak4.jpg

 

 

Wasn't sure if anyone had seen this before or knew what it was, and I guess my google-fu is lacking today, but I thought it was cool!:lol:

 

P.S.
Neat side-effect from the "deep etch" in vinegar, you can see the hardening line for the hammer face!
Hammer vinegar soak5.jpg

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I don't know what it's called, but it sometimes happens when you don't completely submerge the piece.  But that is a bigger buildup then I've seen

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2 hours ago, Jaron Martindale said:

Has anyone seen this before?

Yep, almost all the time.

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What is it..? I guess I’ve just never seen pictures of it before and it was a huge surprise, lol

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12 hours ago, Jaron Martindale said:

What is it..?

Hopefully Alan or other chemist folks will chime in, but I'd guess it's just iron oxide that foams from the heat generated from the oxidation reaction.

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Oxidized iron acetate, probably?  I only see it form at the surface and only if the steel is exposed to the air.  Pretty cool!

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Posted (edited)
3 hours ago, Alan Longmire said:

only if the steel is exposed to the air.

Has anyone noticed that the scale might be removed better (softer) when this happens than when the entire piece is submerged?

Edited by billyO
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I haven't paid much attention the last times it happened.  Maybe some experimentation is in order...

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Posted (edited)

Well, here's a quick sample.  2 billets of 1080/15N20, one 75 layers and one 100 layers, both welded and drawn out at the same time.  The left sided billet was submerged completely in the vinegar and the one on the right was submerged only to the top of the weld (blue line), with the handle portion out in the air.  After 2 days in vinegar (that's been used for at least a dozen or more other billets before these), the one on the right with the end exposed to air had a decent amount of black foam around the top, and the other one didn't have much if any foam floating on the vinegar.  Here's what they look like after getting rinsed off with the garden hose.  Not much wire brushing needed on the right side, and those larger chunks left over will probably pop right off.  The left side is going back in the vinegar. 

20210705_114716.jpg

 

Anyone else want to join in the experiment and share their observations?

Edited by billyO
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