Of course those are cases and not bullets. Cats are notorious for their poor grasp of technical terminology, not to mention their typing and English grammar....
Of course those are cases and not bullets. Cats are notorious for their poor grasp of technical terminology, not to mention their typing and English grammar....
This page is about chemical treatment of steel, but the example shows weaponry. If this would bother you, then you probably should not look at this page. Maybe you should instead look at a page with funny pictures of kittens. Although, as seen in the example at right, even that may disturb some people.
This is not the way to remove blueing from steel, but it is one way to do it. It might work for you. I'm no metal-treating guru.
OK, enough lawyer repellent...
Bluing is an electrochemical passivation process to partially protect steel against rust. That's electrochemical as in chemical reactions which take place in a solution at the interface of an electron conductor (a metal or a semiconductor) and an ionic conductor (the electrolyte), and which involve electron transfer between the electrode and the electrolyte or species in solution. It does not mean that electrodes and wires are involved at all!
Passivation is the formation of a thin non-reactive surface film inhibiting further corrosion. Bluing is therefore the oxidation of the surface of the steel, oxidation in a form preferable to the oxidation of rust. The name comes from the resulting very dark color, really more black than blue.
Rust is Fe2O3, a red oxide that occupies slightly more space per iron atom than iron itself, causing the typically reddish rusting away of iron.
On the other hand, magnetite is Fe3O4, a black oxide occupying the same volume as iron itself. A chemical reaction can form an outer layer of magnetite and provide minimal protection against corrosion. The treated steel must be coated with a thin film of oil, and the bluing is not resistant to wear and is typically no thicker than 0.0001 inches.
Hot bluing is typically done by immersing the parts in a solution of potassium nitrate (KNO3), sodium hydroxide (NaOH), and water heated to the boiling point. Yes, boiling lye, be very careful.
Cold bluing is less effective, and is used mainly for cosmetic touch-up work. Some cold bluing solutions contain selenium dioxide (SeO2).
Parkerizing is another electrochemical method of protecting steel from corrosion, and it also increases resistance to wear. Parkerizing is the creation of an iron-phosphate conversion coating on the outer surface of the steel, producing a grey matte finish.
There are several related techniques, but generally they involve a phosphoric acid solution with key ingredients of zinc or manganese, with varying amounts of nitrates, chlorates, and copper, the solution being heated to 88-99°C, close to the boiling point. So, instead of the boiling lye of bluing, parkerizing uses boiling acid. Nasty at the opposite end of the pH scale.
Different metal salts in the solution produce different colors of non-reflective finish:
| Zinc | Light to medium grey | |
| Manganese | Light to dark grey, or black | |
| Iron | Dark grey to black |
Phosphating, interacting with a coating of cosmoline over several months to years, may produce a light greenish-grey color.
I have a Norinco M1911A1 that was blued. This being produced by Norinco, it was unevenly blued and nearly black. Having seen some nice parkerized finishes, I decided to try to remove the bluing and parkerize it.
Start by completely disassembling it. Here is the slide, photographed on a sheet of white paper. See, nearly black.
Here is a page to help with the disassembly, and eventual reassembly: http://www.m1911.org/stripin1.htm
Here is the 1911 frame.
Clean off all the oil. Something like brake cleaner (basically a compressed spray of hydrocarbon solvents) would do a nice job. As I didn't have a can of that handy at the time, I used isopropyl alcohol in a spray pump bottle. This was common drug store isopropanol and it was 30% water. Good enough to get the job done.
Here is the active bluing-removal agent — white vinegar. See, bluing isn't all that protective after all.
This is marked as being distilled and then diluted to 5% acidity.
All the blued parts that will eventually be parkerized have been disassembled, cleaned, and placed in a glass dish.
Then pour in enough vinegar to completely submerge all the parts and wait. The bluing started to come off after just about 15 minutes or so.
The frame has turned orange-brown after maybe 20 minutes.
Not entirely — see the patches still nearly black at lower left.
I think that what's happening here is that the acetic acid in the vinegar is converting the very thin outer layer of black magnetite to the orange iron oxide of rust.
So what if it ends up being 0.0001" smaller — Norinco fabrication standards are far looser.
You can't really see it here but these parts are submerged in vinegar. The vinegar is clear and only shows up in this picture as the reflection of the flash at lower left.
Every 20 minutes or so I would remove each part and wipe it down with a paper towel to remove the lifted oxidation.
The orange-brown oxide starts to come off with handling.
I seemed to have bare metal everywhere after two hours. I removed the parts, poured out the vinegar, and placed the parts back in the dish. Then I placed the dish under a slowly pouring faucet for several minutes to flush the vinegar.
Then, further careful flushing of each piece and hand drying.
I heated the oven to 250F and placed the parts inside on an aluminum-foil lined pan for about 20 minutes.
That dried the parts, and left some light orange rust deposits.
The next step was rubbing with extra fine steel wool, and then application of a thin film of gun grease.
The next step was to parkerize the metal.
Click here for the page on how the parkerizing was done.
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