Pickling Stainless Steel

[ChazzC]

This article very distinctly describes passivation vs pickling.

Clearly, passivation works best on clean "bare" metal:


And that's the part I need the most help with. The article above talks about using nitric-acid. So back to the beginning...

1. Reduce as much of the need to clean up thermal oxides by not producing them to begin with. Better solder technique, (different flux?)

2. Find the least toxic environmentally safe chemical way to remove any oxides produced that can't easily be removed mechanically.

You may know this already, but be sure to use only stainless steel tools & brushes on your part: steel wire brushes & tools will transfer free iron into the surface and make pickling more difficult. Welders/Mechanics/Mill Wrights on work in food plants keep a separate "Stainless Only" toolbox with safe tools.

 

[dbb-the-bruce]

but be sure to use only stainless steel tools & brushes on your part

Thank you, I was not aware of that specifically for stainless steel. I have experienced the issue with other metals but never to the point of being a problem.

 

[ChazzC]

I’ve seen SS get flash rust after someone used a steel wire brush on it. Contractors wearing work boots ruined a passivated 10,000 gallon liquid sugar tank, leading to unprotected SS surfaces that allowed bacteria growth and a full tank of inverted liquid sugar that needed to be pumped out for disposal and Diversey coming out to clean & passivate a total of four tanks; not cheap.

 

[rwm]

I used food grade phosphoric acid and unwove some carbon fiber sheet to make a brush. I just bunched up some fibers and wrapped them with bare copper wire. Then trimmed the end straight. I have a bench power supply that goes up to 30v.