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Black finish on 300 series stainless

2005

I have about 1200# of 304 stainless machine screws that I want to apply a black finish to. I have no salt spray requirements, only the "appearance" requirement that the parts are uniformly black. Any ideas?

Rich

Richard Pappy
- Williamston, South Carolina

Simplest way to achieve black colour on SS is to oil it (any vegetable oil or even fat or tallow) very sparingly and then heat it (slow!) to max. 400 °C. Instead of oil you can use 20% shellac solution.Chemical process exists.too(1 lit sulfuric acid(d.1,55 gm/cm3),13 gm sodium dichromate,working temp.18-25 C,5-10 min. immersion). Good luck!

Goran Budija
- Cerovski vrh Croatia
2005

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The chemical formulation described in the previous response is indeed a commercially available black oxide for stainless - with sufficient acid to activate, it will black stainless. We do it in bulk fashion nearly every day! It's the most economical way (unless you want to burn oil!).

Milt Stevenson, Jr.
Syracuse, New York
2005

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Birchwood Technologies [a finishing.com supporting advertiser] makes patinas for this purpose. Call us for more info.

Barry Feinman
BarrysRestoreItAll

Carlsbad, California

2005