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Finishing Stainless/Inconel


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Hello All!

Backstory: Poking around the Shenandoah river, I see shiny metal at the bottom. That doesn't happen. Pull it up, its some piece of 3/4" rebar. They were building a new bridge up river at the time, river rose a couple months before and pretty much washed everything downstream. Score. Being who I am, it came home with me to New England. I finally have a purpose for it and have begun to play and see how it forges. Just fine. My question is how can I get it to return to 'in the white' condition? It comes out black when forged and quenched, I've buffed on the wheel (maybe not aggressive enough compound), I can sand of course but that removes a lot of character and right now its in a vinegar bath just to see. Anyone have ideas or experience?

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Agreed, after forging stainless you have to passivate it to restore it's bright appearance and corrosion resistance. Citric acid or nitric acid can be used for this. You can also buy passivation fluid that is made specifically for this purpose. 

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Long soak in citric is the most common these days due to easy disposal requirements and fewer employees at the doctor.  But the pickling paste style from the welding store--really nasty stuff--tends to do a quick job of things.

Assuming you got the scale off there is electro-polishing also but that's a bit overkill.  

I prefer mechanical cleaning then removing any surface iron (which will eventually rust) with citric acid.

Check out this home brew weld passivation using a 12V batter charger.  Cleans up the welds pretty slick.  Explanation starts at 1:30  Might work if your project is the right shape.  Electrolyte doesn't have to be the nasty stuff.


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Quenching in water just to cool it so I can immediately handle and observe. The project is (cough cough) golf ball markers for my son who requested them for his bday. I got to thinking and decided this would fit the bill perfect especially if shiny and not black. He said he's tired of using leaves as markers so I think I'll forge a leaf for him to use.



Thank you all for your responses. I will work with citric acid. September 4th, he could have said something a bit earlier. I will post results when done. Need to do more than read. Thanks!

Edited by LKilby
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If it’s only slightly magnetic, probably 300 series, not harden able. But I would check with a quench and file test to be sure... If it hardens looking more into the 400 series or something else altogether and may take a lot more caution.


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