Black Oxide solution is a two part process. One you mix the contents of a bottle of BO with about 3 gallons of distilled water. (It says do not reuse. But I mean the bucket. You can reuse black oxide as many times as you want.):
Two you cover it with a sealant. That comes in four cans:
You leave the ak parts in the solution for 5 minutes or so. Then wash with water. Then apply the sealant. Then wait for the parts to dry. I left them overnight. IT'S THAT EASY!
For Prep I went overboard (as usual) I sandblasted with alum oxide at 100 psi, wire wheeled using an air die grinder, emory cloth wet sanded, then buffing wheel on bench grinder using black and red rubbing compound. Once I started this process I never touched the ak 47 parts. I used rubber gloves or clean cloth gloves.
After that (I actually did it twice - as I f'ed up and tried to wash the kits in the dishwasher. Turned into flash rust city! That was a bad day. Stay away from the dishwasher unless the parts are already blued. Mine had been stripped from the polishing etc. And completely turned to rust in about 15 minutes.) I started with brake cleaner. Then I used Fabuloso (I think it's Purple Power in other parts of the US.) with hot water from the sink. Immediately drying the ak47 parts with a clean towel afterwards:
I then had Chief ShippingBull (my nephew that does all my shipping and helps me out. LOL!) apply a heat gun to the ak parts. You can get better black by heating the parts or the solution to 120 degrees. You can see how much I stripped the parts in this pic too:
I got these great plastic trays just the right size for a completed AK kit. From:
I made wire hangers out of wire hangers. I also used one of the plastic trays (I bought seperate ones for each operation) to clean parts with brake cleaner. The sandblast media and dirt just kept falling out:
Here's another pic of how polished I started with. I was hoping the black oxide would show off the "hand polished" metal. Like a hot blu would. Make it look like an old firearm that had been carried for years:
You then carefully pour the BO solution into one of your trays (Prior to this I plugged both barrels with wood dowels to keep the BO out. Not sure it would hurt it. But just wanted to make sure.):
Then slide your parts in. And start a 5 minute timer. Although you can go as long and as many times as you like. You really have to be careful here. You need to lift the parts up off the bottom and swirl them around or the solution around them. If you let them just sit on the bottom or on a piece of wire it will not blue as dark there:
After that you take the parts out. And give them a thorough bath. I put them in my cleaning tray and soaked them with water from a hose. I then brought them back in and laid them out in the sealant tray. And smothered them with the sealant using a brush. I left the main part of the kit hanging on the hangers. You can reuse the sealant that flows to the bottom of the tray:
The first kit went off without a hitch. But the second kit ended up with bare areas on the bottom side of the kit. Like bare metal flakes where the BO was not taking. I suspect it was from some of the sealant splashing over from the other tray. Or it could have been oil that seeped out and laid on top of the BO solution:
We fixed this by rubbing each bare part with a rubber gloved hand. The solution won't hurt your hands in rubber gloves. Not sure what it would do to bare skin. But it does not seem to be that caustic. AFter rubbing the areas off. The BO started to take. It made it completely black. (This pic is just a few moments into them fully blacking over. It will scare the crap out of you. Like you messed it up. But have faith. It will all black over):
In the end we removed the kit, washed it with water, heated it up again, and redipped it.
Here are the parts finished. We missed a few tiny flecks on the second kit that had the oil(?) problems. Once cleaned it can be redipped in the BO and would cover fine I'm sure:
(EDIT - At first glance the surface came out looking very painted. Very flat and powdery. I didn't like it. And thought it would look better on an AR than an old school WWII or 60's era AK. But then I polished it LIGHTLY with 0000 steel wool and buffed it with a bare cloth polishing wheel on my air die grinder...)
Like I said above. When it first came out I wasn't to happy with the finish. But then I dried off all the sealant (the next day) and started polishing it very LIGHTLY with 0000 steel wool. Then going over that with a clean cloth polishing wheel on my air die grinder (50 psi). About a 3 inch one so I could get into all the surfaces. It took off the powdery surface that was making it look so flat and painted. And turned this nice translucent brown/grey color.
Cold blu is more on the blue/grey side. But black oxide with the more brown tinge (and I'm talking very slight differences here - I'll post comparison pics later) looks very well suited for a WWII or pre 1960's military arm. I slightly prefer the blue of cold blu. But it just depends on the wood your contrasting it against. A dark walnut brown wood would look great with this. Which is kind of what I have on the Yugo.
The killer app in black oxide (over cold blu) is that you can dip your entire kit at once. Rather than having to wipe each part of it with a small swatch of cloth. Like you do with cold blu. You also have to be careful with flat surfaces with cold blu. Like on the side of a receiver. You have to wipe it cleanly and real flat all along a flat surface. To avoid streaks. With black oxide there is none of that worry. As the entire part or rifle is dipped into the solution.
You do need to take great care that there isn't any oil residue sitting on top of the solution. It might be worth running a cheese cloth over the top to try to soak up any oil sitting on top of the solution. I did miss a couple tiny spots where oil kept the black oxide from the surface of the metal. That can be fixed while in the solution by rubbing it clean. But oil buildup on the surface is an issue to watch for.
Black oxide is a VERY nice finish. It could not have been easier or more even if you tried. The other advantage is there is no caustic chemicals to deal with. No real heat. And you can do it right in your own back yard or kitchen if you wanted to. And for $80 bucks you'll have a solution you can use over and over again. You just pour it back into the plastic bucket it comes with. And you can black oxide as many parts as you like.
I also scratch tested the ak47 parts right out of the mix. With a screw. And it wouldn't scratch with light to normal pressure. And aging with steel wool for areas you want to look worn (like on a bfpu) takes quite a bit of rubbing to even it to start thinning.
For home builders that want a good tough new finish. I recommend this highly. Easy. Cheap. Tough. Hard to mess up. You can't beat it for a new finish on ak parts without using heat or caustic chemicals.