Black finish on steel tools.

[TXFred]

What is the black finish that is found on so many steel tools? For example, the black on a TTS tool.

How does one put this finish on steel?

Frederic

[SteveKoerner]

It's black oxide. In the Phoenix area there are shops that will do a lot of black oxide on a $60 minimum charge. Check the phone book or online.

[shred]

For one-offs, you can try a local gunsmith shop, or if you want to go whole-hog, hit up Brownells for a complete hot-bluing setup.

The cold-blue stuff works ok based on the metal, but isn't really professional.

[wellheadman]

A lot of black finishes on carbon steel and some stainless is called nitride witch is like a heat treat and quinch prosess .It will harden and corrosion resiset the surface of the metal .

[TXFred]

Thanks guys!

Frederic

[JonS]

Search google for "Parkerizing" simple to do if you have a small electro cleaning/plating setup.

[GLCarlson]

There are several "black oxide" processes.

The Top 5 Finishing FAQs

Hot oxide is done by gunsmiths and commercial houses (see the recommended Brownell's catalog for chemistry). It's corrosive, dangerous, and toxic, but difficult to master, and fairly expensive to set up. Don't even think about doing it within sight of precision surfaces. Not even in the same building; the aerosols that get generated travel, and they are corrosive beyond belief. The process produces magnetite on steels. (BTW- don't use anything but welded carbon steel tanks- copper- or any brazing- kills the chemistry). Mostly, unless you're a production gunsmith, "Don't Do It".

Cold oxide generally looks awful in my experience, and isn't a true hot black (that is, it isn't magnetite-it a copper selenide, as I recall). Sort of like plating. I've given up on cold blacks.

Caswell has a system similar to parkerizing. Haven't looked at it.
Cold Black Oxide kit

Birchwood Casey has a 'low temp' (roughly boiling water)true black oxide (magnetite) process that has gotten good reviews. Never tried it, but they claim it'll work on most steels (except stainless) and meets mil spec. Chemistry is about the same cost as hot black.
Birchwood Casey - News
Birchwood Casey - TruTemp®

One can find some fairly silly answers on places like eHow, by the way, which confuse anodizing/dying and black oxide.

None of these, so far as I know, are nitride coatings. Those are usually gold in color. Black oxide is Fe3O4, and while it's modestly corrosion resistant, isn't in the same league as the nitrides/carbides/borides for hardness or corrosion resistance.

If you want to try something really neat, consider the color case hardening process (Guy Lautard described it in one of his books). The chemistry is at least as nasty as hot black, but it sure looks good. Starrett used to use it on some of their holders(probably 50 years ago)- I've got one.

[MichaelHenry]

A guy named "Dix" suggests coating the part with motor oil and baking it in an oven at 350 °F:

The Home Machinist! • View topic - ?Black Oxide Finish?

Mike

[300sniper]

i use the caswell black oxide posted above quite a bit. it works pretty good but i don't think it is the same as what you are after. it works better on mild steel than it does on harder steels. it is incredibly easy to use.

some 1018 parts finished with it:







4140 pre hard:

[TXFred]

300sniper,

That Caswell stuff looks great. I have a question for you. How stinky are the chemicals? My shop is in a garage that opens onto my living room. I have to be very careful of what I bring into the shop, because the smell of it will quickly permeate the house.

[300sniper]

the odor for the caswell black oxide is very minimal. i doubt you would even smell it more than a couple feet away. i mixed it and store it in a 1-1/2 gallon plastic pain with a lid and you definatly won't smell it then. mine has been stored for a long time now and it does have a mildew smell to it when i open the pail and stir it up. the solution doesn't work very good any more either but i expect that after sitting for a couple years.

i woldn't worry about it.

[brian257]

I use precision Brand Tool Black. Precision Brand. I have been very happy with it. I did a product review on it in Home Shop Machinist several years ago. I had some sample parts both with and without the blackening that were left outside for a while and it does a great job protecting the metal. You do still need to keep the parts oiled though for best protection. It is more of a porus surface that holds the oil than a coating.