Post By jackal
Do it yourself black oxide
I've seen adds for low temp plating in many trade magazines. Anyone out there tried this? How's it work? Costs? Results? I have a customer that does a lot of black oxide rush orders and I have a hard time getting fast turnaround at my local platers. Would this be practical in house?
Precision Brand makes a kit called "tool black" and works great. I get mine from MSC.
The newest issue of Modern Machine Shop has a large story about a shop that went to in house black oxide. It sounds like it's worked out pretty well for them.
Nit: black oxide isn't "plating," it's controlled rusting to produce a particular oxide of iron that happens to be black instead of orange.
My understanding is that the "cold" black oxide isn't as durable as the hot-dip process. It works though, assuming you have good surface prep, and it may be good enough for your needs.
The hot-dip process involves some pretty caustic chemicals, so trying to do that yourself would get a lot more involved.
I simmer parts in "tool black" from MSC/Enco over low heat. works really nice on O-1 trigger parts that I make.
but it's just not the same as a professional part. (like an impact socket).
I've tried several of the different "cold black" systems in and my experience none of them come close to the appearance or durability of real black oxide.
They're pretty hit or miss depending on the steel alloy and surface finish also, often you get a "cold gray" rather than black. I've given up on trying to use them.
The last one I tried I thought I had finally hit the jackpot, after pulling the part out of the treatment on a wire it had a beautiful satin black finish. But the next specified step in the process was to wash the part off with plain water, which I did under a slow running faucet, and ended up watching the beautiful black finish wash off and go down the drain, leaving behind a "cold gray" part, about the color of steel after its been TIG welded.
my experience exactly!
FWIW the O-1 works beautifully.
some mystery metal i made some tool holders from was very hard to get the nice rich finish. it washed off just like you say.
but I think it had to do with contamination. not thourough enough degeasing. because I did eventually get a very nice dark gun-blue finish.
buy the "prep" stuff that you can get with the tool black. it's sold together. I didn'nt get it because I figured I can degrease plenty well myself. apparently not. and maybe there is more to it.
Caswell Plating makes an inexpensive kit worth trying. Degrease thoroughly, use distilled water, and you'll know after a few test parts if the kit will work for you.
Actually I've had the best luck doing an in-shop quasi black metal treatment on steel by doing it "blacksmith" style, heat it up and dunk it in some oil (I'm lazy so I actually spray it with CRC or LPS). I don't get a full black this way, you get a dark brown, but it doesn't look bad and gives some protection against rust. I think people doing this more seriously use linseed oil, but that could be a bad memory cell firing.
I've done some firearms with a product called M-20 Antique Black. Some I did black and a few wanted blue. Worked nicely for both. I showed one of the black ones to a gunsmith friend and his eyes got real big. "How did you get that color? I've been trying to get that for a couple years!" Works best when object is warm. For blue a couple applications were done with steel wool. Prep is critical. Clean, clean, clean. When you think it is clean and oil free, clean again.
About 4 years ago, we bought the Birchwood Casey, "low temp" black oxide kit. 190 degrees. Came with 7 buckets, 3 were for rinsing. Two hot plates for the degreaser and the black oxide tank, and a 5 gallons of a rust inhibitor/water displacer, and a test kit to make sure all the chemicals were right. About $600, plus freight.
It was to mil-blah-blah-blah, which is what we needed. Worked pretty well. Got us through the one job we needed it for, saved about $200 plus shipping, plus lead time. Lasted for a few more small jobs after that(probably would have lasted longer if we didn't have an idiot setting it up, and we didn't try to black oxide everything in site). Then we ran out of chemicals, and they are not cheap. The bucket of low viscosity rust inhibitor came in handy many many times though.
Downsides, took forever to heat the 190 degree bucket up on the hot plate, about 3 hours. It was also pretty labor intensive, going from tank to tank to tank to tank, and keeping track of the time in each tank.
depending on your part size and if you would need any polishing
you could call around to the gunsmiths in your area to see if they would
be willing to fire up the tanks when you get a rush job
gunsmith tanks are different than what a plating shop would have
they are usually 6" x 6" x 40" or 8" x 8" x 40"
I second that. I don't recall where I got it but I have the exact stuff. Most likely was an MSC purchase.
Originally Posted by g-coder05
Brownells Magnesium phosphate works great too. Its a parkerize coating that seems fairly tough. I use it on my magazine systems in house. Its simple and always produces a good finish. Depending on the quality of steel it will be from black to dark gray color
I use the Caswell brand all of the time. It works great for my stuff. A large printing company buys spanner & pin wrenches from me. These are made from 4140 round, oil hardened steel, cleaned with carb cleaner, then sand blasted. After that soak them in a bucket of the blackening for 5 min. take out and rinse, then put in the "Diesel -smelling sealer". They're done. Wipe down dry & ship.
about $45 to start with & I haven't opened the 2nd can yet. Done about 135 wrenches so far.
Aw crap, now I've got to try another one of these kits.
Jackal, what color do your wrenches end up after treatment, a true black or a brownish gray/black?
The Caswell Black Oxide kit is excellent. Here is my trick: After your initial soak in the blackening agent, wearing disposable gloves, wipe your part down with a paper towel. Rub hard. Some of the black will come off. When the part is dry, send it back to the "bucket" for another soak. Dispose of the paper towel.
Shampoo, rinse, repeat.
Last edited by Spencer in NH; 09-27-2008 at 05:02 PM.
Ditto on the Caswell Black Oxide kit -- it works great. It contains phosphoric acid, so the final color is more greyish-black, instead of the intense violet blue you get with Birchwood-Casey blue (at Walmart). The Caswell blue isn't a pretty, but it's much more durable -- the Birchwood-Casey you can practically wipe-off with your fingers.
Originally Posted by Spencer in NH
I find the Caswell black gets much deeper if you brush the parts after 5minutes with a nylon brush to remove smut whilst soaking them in the solution.
Then quick wash off with water, into a warm oven to remove moisture, and straight over with a sealer (Although I use BH Autobalm as it gives a better look to the part and doesn't change the dimensions anywhere near as much)
Some I did today: