How to Gray Steel

[Calandrod]

Does anyone know how to get this gray finish onto steel? I really like it and can’t figure out what process was used to achieve it. I put a standard chrome for reference.

 

[Ulma Doctor]

I’m not positive, but I believe it is dipped in a molten salt solution [that I’m unaware of the exact salts used], prior to being ground

 

[pontiac428]

Nitre salts, Brownell's sells them. It's dark and blue-black. Ospho rust is a phosphate pickle, it makes a nice gray color that holds oil for rust protection. Manganese parkerizing is another option (also Brownells) that is gray to black and long lasting.

 

[RandyM]

Caswell has blackening kits also.

Black Oxide Kits - Caswell Inc

caswellplating.com

 

[CJ5Dave]

I used the Rusteoleum version of Evaprust on a Walker Turner drill press. It turned all the surfaces rough gray and I did not want it gray. No amount of oil will make it slick.

 

[pontiac428]

Rustoleum rust dissolver is phosphoric acid with some chromium conversion capacity. If you warm the solution, add a few grams of potassium nitrate, and mix in manganese phosphate (the black outer core of a dead D cell battery), you'll have a blackening solution.

 

[benmychree]

Half and half mixture of sodium and potassium nitrate, with a small occasional dose of manganese dioxide to clean up the bath, operate the bath at 600 - 650 deg F, coat the articles with a thin oil and immerse small articles for about 5 minutes in the bath; this creates a rust resistant blue to black color coating.
This is from the U.S. Armory

 

[MrWhoopee]

The coating is black oxide, @benmychree describes the classic process. There are several others that operate at lower temperatures.
Here's the one I've used recently.

 

[jwmay]

Rustoleum rust dissolver is phosphoric acid with some chromium conversion capacity. If you warm the solution, add a few grams of potassium nitrate, and mix in manganese phosphate (the black outer core of a dead D cell battery), you'll have a blackening solution.

Am I the only one who had a Fight Club flashback reading this?

 

[pontiac428]

Am I the only one who had a Fight Club flashback reading this?

Now that you mention it... But that was just some of what I gleaned from the methods described obfuscated by patent-legalese and utterly buried in this illuminating document: https://patents.google.com/patent/EP0977908B1/en