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topic 33961

How to Darken Stainless Steel


(2005)

Q. I have a piece of stainless steel that I want to darken somewhat. I chose stainless because it will be exposed to a hostile environment, but I want to reduce its shine or ability to reflect light. It has already been bead blasted which has helped a little, but I want more. I noticed some time back that while using an acid drain cleaner [linked by editor to product info at Amazon], it darkened the stainless steel drain collar (may have been chrome), but not the stainless steel sink itself, so I suppose it all may depend on the percent of nickel, etc. in the metal and/or the chemical involved. I could have the piece Teflon coated I suppose, but that is not what I am looking for. I was wondering if there were some not-so-toxic or dangerous chemicals that I could use to darken the metal. I tried the drain cleaner on a small piece of scrap from the same piece, but it did not have the desired effect.

Thanks - John

John Winters
homeowner - hobbyist - Katy, Texas


(2005)

A. Depending on the size, shape, and intended use of this piece this may work. First heat it up to a dull red, then let it air cool, you will have a rather dark finish and it should make most of the surface very dull. Now the two problems I can foresee with this, one it might be too big to heat, two, stainless is a work hardening steel, it needs to be formed cold before it will harden to it's full strength (so if it is going to have heavy wear and tear, it wouldn't be a good idea to use this method).

Alternate idea? Coarse wire brush.

Marc Banks
- Elizabeth City, North Carolina


(2005)

A. You can oil and then heat it to 200-400 °C (oil it very sparingly), or you can use 50 gm sulphuric / 200 gm sodium thiosulphate/1 lit water solution, temp. 30 °C.

Good luck!

Goran Budija
- Zagreb , Croatia


(2005)

Q. John, have you tried that sulfuric acid + sodium thiosulfate solution on the stainless steel to see if it darkens it as much as you like.

Raymond Fry
- Beaverton, Oregon


(2006)

Q. I have a unique problem, I need to take the shine off stainless steel strips. They are used as constrained layer dampeners on coal wagons for noise reduction but are extremely reflective which draws some complaints.

It might be a big ask but any ideas for environmentally friendly solutions (besides the obvious painting and mechanical finishing). The finish just has to be dulled down a bit to lose some of its reflectance.

Paul Baxter
engineering - Newcastle, NSW, Australia


September 17, 2009

A. Hey Paul,
Mechanically you could orbital sand the stainless. This will create a matte uniform finish.
Chemically you can remove the strips and have them passivated or pickled. This will turn them matte grey and a more homogeneous finish. Depending on the reputation of the shop you decide to use will determine if it is environmentally friendly or not.

Cliff Kusch
electropolishing shop - North Vancouver, British Columbia, Canada


(2007)

Q. I have a wristwatch with a stainless steel case. I very much like the shape, but not the stainless steel finish. I would like it to be darkened, gun metal or darker. Do you think any of the above would work? Would the color be somewhat consistent? Thanks, Ron

Ron Packard
- Los Altos, California


August 9, 2011

Q. My question is similar in nature to the above but another twist on the unusual. My husband recently passed away and we are having him cremated. My sister picked out an urn - bright copper colored stainless steel. I would like to 'age' it a bit or at least tone down the brightness. Any suggestions?

Sheryl Kyrisch
- Atlanta Georgia USA

October 9, 2012

Q. Has anyone tested the 50 gm sulphuric acid + 200 gm sodium thiosulphate + 1 lt water solution to darken stainless steel?
Which dilution is the 200 gm sodium thiosulphate? I got some difficulty to get the sodium thiosulphate but I can get photography solutions based on that with a 2% solution in water? Is this enough?
thanks
rui

rui moreira
- ovar, portugal



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