Black Oxide vs. Bluing

[88E30M50]

What's the difference between a black oxide finish and a blued finish? I think a blued finish is a form of oxide and both are a byproduct of a chemical change to the surface of the metal. The old Colt black army was a black oxide finish, right? You also tend to hear the two used interchangably from time to time such as when referring to a Remington R1. Some call it a blued finish but the website calls it a black oxide finish. Can a modern production black oxide finish be polished out like a blued finish or is a production black oxide finish something completely different?

 

[midget]

You polish the metal before having the black oxide done and it turns out looking like this (slide):

 

[engineerpower]

Rust bluing and black oxide are after the same thing. You're trying to get a layer of Fe3O4 (magnetite) to form on the surface to prevent the underlying steel from oxidizing into rust (Fe2O3).

Rust bluing is allowing Fe2O3 to form, then converting to Fe3O4 in boiling water.

Chemical oxidation may use other reagents or physical processes in the conversion.

 

[88E30M50]

Thanks to both of you for the info. If I'm understanding it correctly, a black oxide finish is essentially the same as a rust blue finish and that the quality of the finish is going to reflect the quality of the prep before hand. The factory black oxide finish is achieved directly as opposed to the two stage rust blue finish but both end up with a surface coating of Fe304. Am I understanding that correctly?

 

[midget]

Thanks to both of you for the info. If I'm understanding it correctly, a black oxide finish is essentially the same as a rust blue finish and that the quality of the finish is going to reflect the quality of the prep before hand. The factory black oxide finish is achieved directly as opposed to the two stage rust blue finish but both end up with a surface coating of Fe304. Am I understanding that correctly?

Correct.

This is what I use and have had great success. http://www.caswellplating.com/metal-finishing-solutions/black-oxide-kits.html

 

[engineerpower]

Pretty much, the industry has been trying for generations to find the fastest, most economical process to finish parts that meet quality expectations.

Caswell (among others) sells kits that do the direct blackening at room temp. Here's the link to give you an idea:
Black Oxide Kits - Metal Finishing Solutions - Caswell Inc

You can buy kits and solutions to do a "cold blue" but it won't be the same as a rust blue, and is pretty much universally considered an inferior finish.

 

[88E30M50]

That's interesting stuff. Can the room temp black oxide kits be applied multiple times to control the depth of the finish as with rust bluing or are they a more one-shot finish? I like the fact that it's a pretty safe process to use as compared to hot bluing and it seems easier than cold bluing. I've had good success with cold bluing but only for a short time. The finish does wear quickly with corners showing bare metal within a week or two of normal use when using cold blue.

 

[midget]

That's interesting stuff. Can the room temp black oxide kits be applied multiple times to control the depth of the finish as with rust bluing or are they a more one-shot finish? I like the fact that it's a pretty safe process to use as compared to hot bluing and it seems easier than cold bluing. I've had good success with cold bluing but only for a short time. The finish does wear quickly with corners showing bare metal within a week or two of normal use when using cold blue.

When I use it, I do multiple submersions and brandish with 0000 steel wool in between.

 

[engineerpower]

I really want to make a pun about brandishing other tools while working on my guns, but I will take the nobler path here...

This isn't indianashooters, after all.