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Will Wilcox

Blackening Stainless Steel

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Hello everyone. 

I have a project in mind which requires a black finish on stainless steel. I am not considering paint, for various reasons. 

The parts in consideration will be machined from 303 stainless. 

Im almost certain you cannot blue stainless, yes? Seeing as how bluing is nothing more than controlled oxidation, and stainless is intended to be oxidation-resistant, 

Are their any alternative ways to blacken stainless? As i said, paint is not an option, as the finish needs to be fairly abrasion resistant.

Machining the parts from mild and then bluing them crossed my mind, but i already have the 303 in the sizes i need, and would prefer to use what i have if possible. 

Thanks. 

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I have used a stainless steel blackener that I bought from caswells for some projects at work.  I ended up with more of a grey finish that a true black, but that was all I needed, so I didn't try to push it any further to see if I could get a deep black.

https://www.caswellplating.com/stainless-steel-blackener-8-fl-oz.html

I know you can buy stainless hardware that has a "Black oxide" finish, so there must be a method of doing it.

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Thank you, Brian. 

Did you dilute the blackener at all when you used it? Or was it full strength? 

 

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2 hours ago, Will W. said:

Thank you, Brian. 

Did you dilute the blackener at all when you used it? Or was it full strength? 

 

I used it full strength.  The parts we were working with were all 304 which I would expect to be slightly more oxide resistant than 303. 

Actually, come to think of it, I have some 303 scrap parts at work.  I'll dunk them and post a pic for you.

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This is a piece that was made from 303 that I just dunked in the blackener.  It looks a little darker in person than it does in the photo.

Caveats:  I didn't clean the part real well, I just let it sit in acetone for a few minutes.  I also didn't follow the instruction on the etcher.  It says that 300 series steels should be pre-etched in muriatic acid prior to blackening. (I don't have any available or I would have done that)  I would assume following the instructions would yield better results.

IMG_20180615_130859935.jpg

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2 hours ago, Jim Kehler said:

If you heat up your pieces in your forge they will be black.

This.  Get a layer of tight scale on it and oil it.  It'll be as close to black as it can get.  Not shiny, unfortunately, but blackish.

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If its within the scope of your project, you could send the parts off to be DLC coated. This is not a paint. Its a PVD coating that bonds with the metal surface. It is very tough.

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3 hours ago, Jim Kehler said:

If you heat up your pieces in your forge they will be black.

I considered this, but im not sure how scaling would affect my tolerances, which honestly are not all that tight, but still. Its my last resort. Worthy of trial and error at the very least. 

That part looks good for just a quick trial Brian. Thanks for the photo. I think im going to give this a shot first.

Thank you for the recommendation, Shane. I will look into it. 

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 You could try Sculpt Nouveau Stainless Black

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Looks like a good product. Thank you.

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