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Sulfamic Acid

Mon May 26, 2014 7:43 am

Anyone ever use sulfamic acid to force a patina? Looks like the patina it forces can be jet black and if left on long enough it will even patina stainless steel.

Its a pretty heavy duty acid. A lot of silver polish and tarnish removers have it as an active ingredient as well.

Re: Sulfamic Acid

Mon May 26, 2014 1:07 pm

I've seen varying opinions on whether the patina formed by sulfamic acid is indeed protective. If I was going that route I would probably try rust blue, aka Belgian blue. Stay away from nitre blue due to the high temps required.

Cheers,

Rick

Re: Sulfamic Acid

Mon May 26, 2014 7:07 pm

Ferric chloride

Re: Sulfamic Acid

Mon May 26, 2014 10:53 pm

That stuff sounds even better. I would probably just stick with boiled apple cider vinegar I'm not a chemist hah so i'm not gonna be messing with anything crazier just curios to see who gets hardcore and busts out the real acids.

Re: Sulfamic Acid

Tue May 27, 2014 4:13 am

COP<> Ferric Chloride is a popular etchant. Nitrates and nitrites passivate steel, as has been discovered by those who tame reactive knives with salami or corned beef (what I use). What I was trying to point you towards is rust bluing, which combines the two, adds nitric acid, and often throws in a secret sauce. The secret sauce isn't gonna be something easily sourceable.

I'm considering trying this on one of my white #2s.

http://www.brownells.com/gunsmith-tools ... d9815.aspx

Cheers,

Rick

Re: Sulfamic Acid

Wed May 28, 2014 12:32 am

The gunsmith solution is interesting, I would make sure its food safe before putting it to knives

Re: Sulfamic Acid

Wed May 28, 2014 3:51 am

The formula I linked to should be food safe. Herter's original Belgian blue formula contains mercury salts. Not sure if any sticks around to play Mad Hatter after the distiller water boil, but I wouldn't chance it.

Cheers,

Rick

Re: Sulfamic Acid

Wed May 28, 2014 2:56 pm

A blued knife is going to make food taste bad.

Re: Sulfamic Acid

Fri May 30, 2014 5:00 pm

Jason<> Not poking a finger in your eye here, but do you have any experiences to back that up? Because chemically a rust blued knife should be identical to one with a natural patina.

If I get the urge I might try Mark Lee's Express Blue #1 on my white #2. When I get the MSDS I will post ingredients in this thread. Only problem is that the Sakai Yusuke isn't a problem child wrt reactivity (barely reactive) so I would only be doing it for aesthetics. And I don't want to dork up my new Kono Fuji. Hmm.

Cheers,

Rick

Re: Sulfamic Acid

Sat May 31, 2014 10:53 pm

I can't speak for all bluing, I used cold blue many years and was unhappy with the overall results. I've use onions, lemons, vinegar and currently ferric chloride, I'm sticking with the ferric chloride.

When it comes to knives I've tried about everything ;)
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