On 9/24/2010 10:31 AM, Scraper wrote:
On Sep 23, 10:53 pm, "David R. wrote:
Durable cheap finish for home built receiver

I recently finished a home made AR-15 receiver made from 304 SS and
6061-T6 AL. Now I want to give it a cheap flat black or dark gray
finish, preferably something I can spray on and maybe bake in the oven.
I remember a discussion something like this a while ago, but I can't
locate it.

Any ideas or suggestions, either for the process or locating the discussion?

David

Black oxide is available for stainless, but it leaves a thin coating
that's not tough at all. Black nickel is better but it's really gray,
not black. Black chrome is best but also the most expensive. You'll
have to send out to have those finishes put on but you can do the
black oxide with a Caswell kit. If you want the receiver to look
bright for a long time, black chrome is the trick. You may have seen
that finish on good handguns.

There are lots of ways to blacken aluminum. Commercial treatments use
alkaline or acid treatments. Most of them are gray, too, and you won't
get a good match with the stainless.

You can have the aluminum parts anodized and treated with black dye.
The old dye used for this was black India ink. It doesn't sound like
much, but the anodized treatment is tougher than the alkaline and acid
treatments. You can't do this with hard anodizing, which really is
only thick anodozing, it's not any harder. It has to be a standard,
thin anodize and you have to dye it right away, while the anodizing is
still porous. It seals itself up in humid weather, and it happens in
days, or even hours, and then it won't take dye. You should send out
to a jobber for this, too, unless you want to experiment and you know
how to do anodizing.

If you want a uniform color on the stainless and the aluminum,
powdercoat is the way to go. It's not especially tough, but it's cheap
and it can look good if you don't beat your guns around or let them
bang into hard things. I never heard of a bake-on spray paint, except
for muffler and manifold paint. I don't think that would look good.
Bake-on barbecue paint I've seen is flat black.

When Remington first started making stainless shotgun barrels, in the
sixties, they had them iron plated and then hot tank blued. It was a
really good finish. It was expensive to do in small batches.

I hate color finishing stainless because it's hard for the small-time
operator to get a smooth and even job. I used to blue guns as a
sideline. I'm not an expert. I only applied hot-tank and cold-blue
finishes. A real cold blue, sometimes called rust bluing, can be
beautiful, but I never heard of a process that works on stainless.
Check with Brownells to see if they make such a thing. Sometimes it
comes out purple, anyway, on alloy steels.

I know about these options, but I'm looking for CHEAP.

David