plating, anodizing, & finishing Q&As since 1989
Removing annealing stains from stainless steel
Q. I'm looking for a solution to removing discoloration of stainless steel after it has been heated in the spinning process (Annealing) Grinding and sandblasting will not give a suitable finish. If there is a acid bath that will pickle the material to a even gray color this would be acceptable. Thank youChuck Freeman
- Orange Park, Florida
A. Hi Chuck ,
You could try the following mixture :-
- 18 % V/V Nitric Acid
- 6 % V/V Hydrofluoric acid
- 2 % V/V Hydrochloric Acid
But be warned this is no mixture for an amateur to play with , the Hydrofluoric Acid is EXTREMELY dangerous and the SLIGHTEST splash on your skin will give you the MOST painful burn that you will ever experience, and the treatment is even worse
John Tenison - Woods
- Victoria Australia
A. Is it safe to assume you are referring to 300 series austenitic steel?
If the stainless is just oxidized (i.e., brown), merely dip it briefly in hydrochloric acid (0.5-1 normal) and then rinse thoroughly. The oxides are readily soluble and are quickly removed. Don't let the stainless stay in contact with the HCl for too long, as the chromium component in the metal is soluble in the acid and you will damage the part.
SCSC - State College, Pennsylvania
Q. Hello, we've had a little problem on a job, the kitchen sink got splashed with caustic soda
, leaving dark stain marks? The question is: how can we clean it up? Thanks for your help
building and decorating - Alexandria, NSW, Australia
Q. Problem is there are discolorations 'stainlike' and irregular in pattern on the polished portion of my ss sink. When these stains are wet they disappear. As soon is it dries they reappear exactly the same. What can I do to keep them invisible ?
- LaSalle, Ontario, Canada
Annealed SS tubes come out green or black
Q. We annealing some ss 304 tubes at 1000 degrees Temperature--some tubes comes out with green colour sometimes black color
Kindly let me know the right process.
Manufacturer - India Bangalore
September 4, 2018
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