Black oxide vs blue

scout308 · February 17, 2014, 12:56 PM

can someone explain the basic difference......I can obviously read the interweb descriptions, but can someone boil it down to gun guy differences......

Thanks

Wyosmith · February 17, 2014, 01:40 PM

Black Oxide on Steel is "Blue".
Also known as Ferric Oxide or Ferro Ferric Oxide.
Not all "blue" is black oxide however.

For example the screws on these flintlocks are temper blued. This kind of bluing is done by heating the steel to 620 degrees. Best results are obtained when the heat is done without the presents of oxygen.

Dixie Gunsmithing · February 17, 2014, 02:06 PM

I take it you may be asking what the difference is between hot rust bluing, and caustic bluing? If so, there is a difference in the chemicals and the color.

Cold bluing forms a blackened oxide, and generally uses a selenium compound, with other chemicals, and it doesn't wear well.

Hot rust bluing is done by heating the polished part in boiling water, then applying an acidic mixture to the steel, which forms a blue-black rust. The original formula varies from some of the newer ones, but it is mainly nitric acid (spirits of nitre) based, with some form of iron added. One of the original formulas was nitric acid, and a handful of iron nails in a solution.

Caustic bluing uses a mixture of water and lye salts, which can be mixed with another hydroxide. The polished part is boiled at a higher temperature than the above, at around 180 Deg. F., for about 30 minutes, and when it comes out, it is black.

One hot finish, compared to the other for wear, is about the same, IMO.

Pahoo · February 17, 2014, 02:09 PM

My wife, use to work for a tool company and many of their tools went through a Black-Oxide process and the color was blacker than the blue. The process was similar to the blue salts process that we are use to. I believe it's a less expensive process and most of your "black" general hardware, have gone through the black oxide process. I would send gun parts to have this done and the average person would not tell the difference. ......

Quote:

True gun bluing is an electrochemical conversion coating resulting from an oxidizing chemical reaction with iron on the surface selectively forming magnetite (Fe3O4), the black oxide of iron. Black oxide provides minimal protection against corrosion, unless also treated with a water-displacing oil to reduce wetting and galvanic action. A distinction can be made between traditional bluing and some other more modern black oxide coatings, although bluing is a subset of black oxide coatings.

Be Safe !!!

James K · February 17, 2014, 09:48 PM

The process usually used on machine tools and the one once used on many guns is carbonia bluing, which is done by the use of chemicals in a gas furnace. It is part of the heat treatment process and gave the hard black color once seen on Colt and S&W revolvers. But it is an expensive process and can't be repeated, so factory refinishing was done by caustic salt (hot tank) blue.

(The very shiny, "mirror" surface was due to the high polish given the parts, not to the bluing process itself.)

Jim

Scorch · February 17, 2014, 10:00 PM

What most of the entries above say is true. However, "bluing" is a generic term, and black oxide bluing is a specific term. The caustic bluing typically used on firearms is a mixture of various hydroxide (typically (NaOH, KOH, and others) along with specific metal salts that enhance the color achieved.

James K · February 18, 2014, 12:04 AM

If one wants a really shiny black finish, one way is black chrome. I have seen several guns done that way and, while it is not to my taste, it really does attract attention!

Jim

Elerius · February 18, 2014, 02:33 AM

Can slides for handguns be temper blued? Those screws look really nice and I can imagine how nice a pistol would look like that. The closest thing I've seen is nitre blue which as i understand it, wears off very quickly

Dixie Gunsmithing · February 18, 2014, 10:08 AM

Quote:

Can slides for handguns be temper blued?

No, not really. The temperature to reach the blue color is over that which most frames/slides and barrels are taken for hardness. In effect, it would soften them.

Dixie Gunsmithing · February 18, 2014, 01:00 PM

James,

Birchwood Casey offers an industrial cold blue process that they claim is tough, and uses several chemical tanks in the process, but I wonder how 'tough' it really is, as I have yet to know a Gunsmith or gun manufacturer to use it.

Black chrome was one process Winchester used on the 94 frames, or what the instructor told us during their training class years ago. I think another was iron plating, then caustic bluing.

February 17, 2014, 12:56 PM	#1
scout308 Junior Member Join Date: January 14, 2009 Posts: 9	Black oxide vs blue can someone explain the basic difference......I can obviously read the interweb descriptions, but can someone boil it down to gun guy differences...... Thanks

February 17, 2014, 10:00 PM	#6
Scorch Senior Member Join Date: February 13, 2006 Location: Washington state Posts: 15,248	What most of the entries above say is true. However, "bluing" is a generic term, and black oxide bluing is a specific term. The caustic bluing typically used on firearms is a mixture of various hydroxide (typically (NaOH, KOH, and others) along with specific metal salts that enhance the color achieved. __________________ Never try to educate someone who resists knowledge at all costs. But what do I know? Summit Arms Services

February 17, 2014, 01:40 PM	#2
Wyosmith Senior Member Join Date: December 29, 2010 Location: Shoshoni Wyoming Posts: 2,713	Black Oxide on Steel is "Blue". Also known as Ferric Oxide or Ferro Ferric Oxide. Not all "blue" is black oxide however. For example the screws on these flintlocks are temper blued. This kind of bluing is done by heating the steel to 620 degrees. Best results are obtained when the heat is done without the presents of oxygen.

February 17, 2014, 02:06 PM	#3
Dixie Gunsmithing Moderator Emeritus Join Date: April 27, 2013 Location: Ohio Posts: 1,923	I take it you may be asking what the difference is between hot rust bluing, and caustic bluing? If so, there is a difference in the chemicals and the color. Cold bluing forms a blackened oxide, and generally uses a selenium compound, with other chemicals, and it doesn't wear well. Hot rust bluing is done by heating the polished part in boiling water, then applying an acidic mixture to the steel, which forms a blue-black rust. The original formula varies from some of the newer ones, but it is mainly nitric acid (spirits of nitre) based, with some form of iron added. One of the original formulas was nitric acid, and a handful of iron nails in a solution. Caustic bluing uses a mixture of water and lye salts, which can be mixed with another hydroxide. The polished part is boiled at a higher temperature than the above, at around 180 Deg. F., for about 30 minutes, and when it comes out, it is black. One hot finish, compared to the other for wear, is about the same, IMO.

February 17, 2014, 09:48 PM	#5
James K Member In Memoriam Join Date: March 17, 1999 Posts: 24,383	The process usually used on machine tools and the one once used on many guns is carbonia bluing, which is done by the use of chemicals in a gas furnace. It is part of the heat treatment process and gave the hard black color once seen on Colt and S&W revolvers. But it is an expensive process and can't be repeated, so factory refinishing was done by caustic salt (hot tank) blue. (The very shiny, "mirror" surface was due to the high polish given the parts, not to the bluing process itself.) Jim

February 18, 2014, 12:04 AM	#7
James K Member In Memoriam Join Date: March 17, 1999 Posts: 24,383	If one wants a really shiny black finish, one way is black chrome. I have seen several guns done that way and, while it is not to my taste, it really does attract attention! Jim

February 18, 2014, 02:33 AM	#8
Elerius Senior Member Join Date: August 8, 2013 Location: Seattle, WA Posts: 365	Can slides for handguns be temper blued? Those screws look really nice and I can imagine how nice a pistol would look like that. The closest thing I've seen is nitre blue which as i understand it, wears off very quickly

February 18, 2014, 01:00 PM	#10
Dixie Gunsmithing Moderator Emeritus Join Date: April 27, 2013 Location: Ohio Posts: 1,923	James, Birchwood Casey offers an industrial cold blue process that they claim is tough, and uses several chemical tanks in the process, but I wonder how 'tough' it really is, as I have yet to know a Gunsmith or gun manufacturer to use it. Black chrome was one process Winchester used on the 94 frames, or what the instructor told us during their training class years ago. I think another was iron plating, then caustic bluing.