Hey, welcome back to Albany County Fasteners - Fasteners 101
I'm Bob and today we're going to talk about the black oxide process. So let's get started.
Black Oxide. What is it?
Black oxide is a conversion coating formed by an alkaline-salt solution.
There are two processes in black oxide: you have a hot process and a cold process.
The cold process does not meet government or mil-spec (military specifications) and will have color variations.
There are four different classes with black oxide.
Black oxy has classes 1 through 4.
The typical ones being used are classes 1 and 4, for fasteners.
Class 1 basically runs between 285 degrees and 290 degrees as the process is baked.
Class 4, which is for stainless steel, is a 250-degree process.
So what I have here presently right now are fasteners that had been black oxidized from stainless.
These are all stainless parts that have been sent out and
had the black oxide process applied.
Some of these parts have different finishes,
as far as how dark in pigment they are versus others.
The flat washers as you can see here
have some minor scratches or imperfections and washers are not always
going to be totally one hundred percent black.
You can see some variations in some of them. Some will be purely black.
I've seen them both ways. Sometimes we send them back for reprocessing.
It's just the nature of the process that you have to deal with,
like this socket cap screw which I've seen this time and time again, I have two here:
I have a larger one and a smaller one. The smaller one is a little darker than the larger one.
The larger ones almost have more like a pigmented gun finish.
With that process you can have different patinas on them.
It's all a matter of how they process and how long they put it through the process to complete it.
For some of these, the typical process for black oxide is: rinse, black oxidize, rinse again, finish coat.
That's the typical finish.
We stock a lot of black oxide products.
A couple of products here that can be done, that we don't have here presently, are nylon lock nuts.
They have a nylon part in those and they need to be
protected before they go through the process so it does not change
the physical condition of the nylon so it locks the nut in place.
I want to go through the five basic steps for black oxide which are clean, rinse, black oxidize, rinse again,
supplementary finish. The supplementary finish is what protects the black oxide
for a long, long time.
The coatings are oil, wax, paint, or lacquer.
So dependent upon
your condition and what you're applying this to,
that will change how you finish your black oxide.
So this particular one, this button head, has wax on it.
This was put in wax, spun, and finished.
The typical process for black oxide is black oxidize and then oil, spun off.
That is the typical when someone does not specify.
So oil finish will give you a glossy finish.
Wax finish will give you a matte finish.
Paint or lacquer will give you a satin finish or a glossy finish dependent upon what you specify.
It all depends on what you want your black oxide to be.
We can send your product out if you want us to and have it done to your specifications.
Black oxide on stainless will yield excellent corrosion protection primarily
due to their inherited properties.
So when you black oxidize stainless chances are it's going to be more resistant to corrosion.
Now keep in mind that a black oxide finish with oil in a saltwater condition
will eventually show some type of rust.
Same thing if you put black oxide on your car or your truck and you
drive the vehicle in salt on the streets, you will see corrosion on the fasteners.
So you're going to want to
coat your black oxide accordingly, and that's really what it comes down to.
We have a customer who sells his product that he puts our fasteners into
and with those fasteners he first has them black oxidized.
He then sends them out to be painted black and then he lacquers it.
So, when it goes into a saltwater environment he will not experience, or his customer will not experience, any rust.
Or another way to prevent rust would be to black oxidize 316 stainless.
That should, you know, finish it but 316 is very expensive, it's not cheap, so you have to pay for that.
As far as hot and cold finish go,
these are all parts done in hot black oxy.
Cold finish, how you can tell is, cold will start to rub off.
You can take your hand and you can rub it
and the black oxide will rub off. This will not rub off (Hot Process Black Oxy).
So the hot process is the best process. Cold process will chip,
it will scrape, you will have issues
as far as black oxide goes in a cold finish.
Colors will change if you're using black oxide and a 900 degree or higher environment.
So if you're going to put the black oxide parts into nine hundred, one thousand degrees,
you're going to see variations in the color happen as it's in that environment.
If you're going to have your parts black oxied and your parts are rusty or scaling,
you will need to have the parts clean before they can be black oxidized.
In other words it would have to go into an acid pickle to clean the parts and
then rinse them back off again and then go through the process of black oxide.
Plated parts such as alloy with zinc plating on it or alloy with hot-dip galvanized plating;
all those plating's would have to be removed prior to black oxying.
Black oxide only works on alloy or stainless steel
products that are free of any other foreign products on it.
So no oils, no grease, no plating's, it's got to be clean parts.
Plating can be done directly to alloy parts or stainless steel parts
series 18-8, 300, and 400 series.
Anything other than that, a 316 or other special stainless's, will require
to be reviewed for how dark you're
plating will be as far as-or your
black oxide process will be.
Welding black oxide does not produce noxious fumes or hamper the ease which parts can be welded.
So in closing of black oxide, this is a process that many
gun dealers, knife, and car products use this type of hardware in their applications.
It's an awesome look; people love it.
We stock loads of this stuff and we also send out custom orders for processing.
There you go. Today you learned about the
black oxide process; the cold and hot process.
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