Black oxide coating

[Ray C]

Guys,once the part is oxide does this keep it from rusting or is it just mainly for looks?I'm doing a mill and some of the parts have the black oxide finish but where fingers have been you can see through the bluing and that is where its rusting some.Can the bluing be stored till the next time its needed??Sorry my mind is going 90mph,I can see me adding this to my finishing process----kroll

It's a rust preventative. Actually, the oxide treatment itself is a type of rust but, it's combined with other molecules that prevent further rust caused by moisture and oxygen.


Ray

 

[John Hasler]

It's a rust preventative. Actually, the oxide treatment itself is a type of rust but, it's combined with other molecules that prevent further rust caused by moisture and oxygen.


Ray

Well, a rust retardant, anyway. Stuff that has been Parkerized should be kept oiled with just enough light oil to fill the pores in the coating.

There are lots of variations on this process, and some are far more durable than others. As a general rule the easier it is to apply the more quickly it wears off.

 

[rmack898]

Thanks for the suggestion's guys. Ray that product from Caswells looks like it will be just what I am looking for. I'll order it today and give it a try.

 

[uncle harry]

Well, a rust retardant, anyway. Stuff that has been Parkerized should be kept oiled with just enough light oil to fill the pores in the coating.

There are lots of variations on this process, and some are far more durable than others. As a general rule the easier it is to apply the more quickly it wears off.

Some years ago I was fortunate to purchase about a ton & 1/2 of grade 8 black oxided fasteners of all sizes & configurations. The company discontinued black oxide since it rusted. They were right & I scored thousands of dollars worth for $ 400.00.
(Sort of an implied gloat)

 

[Ray C]

Well, a rust retardant, anyway. Stuff that has been Parkerized should be kept oiled with just enough light oil to fill the pores in the coating.

There are lots of variations on this process, and some are far more durable than others. As a general rule the easier it is to apply the more quickly it wears off.

Yeah, I hear what you're saying but, I've had really good results from this stuff IF (and only IF) I clean and treat the parts properly. On all the brackets I make for the yachts, I use this product -and that's why I go through 2 gallons a years. Anyhow, the parts I'm making are in the engine compartment but, it's still a sea-water exposed area and the finish is holding up on parts I made several years ago -but I don't expect it to last forever.

Anyhow, I can't stress enough to completely degrease the parts first. I use 90% rubbing alcohol and really wash them good. After that, the rubber gloves go on and I blow dry them and heat them in the toaster oven to about 120-130F (roughly). I use an old photo-processing tray to dunk them in. The tray must be just as clean as the parts. All of this cleanliness is really important. At no point from start to finish should you handle things with your fingertips as skin oil will mess things up. It even contaminates the stock solution in the tray. I also use the sealer/glossy product they have which is some kind of penetrating oil. After the treatment, I warm the parts in the toaster again for 10 minutes and let them cool. If you go to all this trouble, the finish is pretty darn good.

BTW, for the edification of those who are curious, this process is based on phosphoric acid etching.

You're right though, all Parkerizing and black-oxide processes are not a rust preventative but, a rust retardant. That is indeed true.


EDIT: One other tip. If you have a piece of hardened metal and if it's pretty smooth, it helps to lightly sandblast the part to abrade the surface. This allows the etching solution to do a better job.


Ray

 

[Ray C]

I have a batch of parts that need treating and if the UPS guy shows up with the threaded rod today, I'll post a step-by-step procedure later today... I've got one boat part and a bunch of clamping fixtures I made for my own needs. Good demonstration material...


Ray

 

[Kroll]

Please do Ray,I would love to learn more about this.Over the yrs I have always painted parts black that were black oxide.But on thread parts they were just strip but not painted,keep was on those type of parts.This is a good post thanks rmack----kroll

 

[Jamespvill]

If a DEA agent ever visits your place, make sure you tell them right away what that's for. And whatever you do, don't leave your supply of Sudafed tablets laying around....



Ray

Hehe, How else do you expect me to pay for all my machining habits? Ain't no rest for the wicked!

 

[old cone]

I do a few small parts for guns and I dip them in oil, engine, lubricating, what ever comes to hand and burn it off with a torch. Then I heat it until the remainder of the oil smokes then quench (dip) in oil for a black finish. My son recently finished a pilot run of small steel parts and lamented that he would have to pay minimum for black oxide so I told him of this old gunsmith trick which he used to great success.

 

[astjp2]

I just dropped some parts on Ospho from the local true value...be careful though, it can remove base metal if left too long. Tim