Switchblade cleaning, maintenance, and storage

[Peiper]

I have a few questions concerning cleaning, maintenance, and storage. My first question is what are the grey deposits on the metal of this Coricama? Grey rust? Carbon? How do prevent it from becoming worse? Is there any way of removing some of it without having it professionally cleaned? Will this affect the value? I store all of my switchblades in the open position in storage cases.

Thanks,
Peiper

[Bill DeShivs]

It looks like someone put the blade in a phosphoric-acid based rust remover.
The steel is actually frosted.
Mechanical polishing is about all that can be done.

[Peiper]

Is that grey rust?

[Peiper]

It looks like someone put the blade in a phosphoric-acid based rust remover.
The steel is actually frosted.

Bill, I think the flash from the camera gave it the frosted look. Here it is without the flash. Any difference?

P.

[jerryk25]

If you look at a really old blade, like an American Press Button. It will be grey.
And it will have black streaks in it, and it goes deep, not just surface black.
It might be very smooth, and look like it has a Laquer Varnish. . . .it will not "mirror polish".
Even if you DID manage to polish it bright (not advised), the black and grey will come back.
Sometimes the metal simply wants to stay grey. . . The metal is old. . .it is oxidizing deep.
Black rust.

Ferrous Metal Alloy is a porous crystalline matrix. . . Heat it, it expands, add carbon and cool it fast, it traps carbon.
Think of Marshmellows in glue with peas in it. . The ratio of globular structures are named. Austenite is one type.

I saw a Lady metallurgist hone a metal shard and polish the surface, to look at it under polarized light in a microscope.
It was a multicolored oil in water irridescent field of Jack Frost splinters.
She was developing recipes. . .tables of time and temperature. . .to make Neodymium Iron Boride Magnets.
And how the structure cooled, changed the matrix, affected the ability to stay magnetized under stress.
It is these matrix patterns that are sometimes random. . . that affect the coloring in old metals.

Reheating a magnet wrecked it, made the "peas" in the "glue" clump together into unwanted "marshmellows".
And when the specimen was re-magnetized by an electro-magnet coil exposure, it was never again 100% good.
Oxides within the steel matrix would migrate. . . . Surface Oxides would penetrate deeper.

I also read in a book on old Samurai swords a saying . . ."Red Rust Bad. . .Black Rust Good".
That you should not try and stop black rust on an old Samurai blade. . . It is inevitable.
Black rust is stable to a degree. . .Red Rust tends to flake off surface metal.

She explained that the very nature of the recipe, if the steel had trace magnesium in it, or an intentional additive,
like Molybdemun to make it flexible, or Vanadium to make it tough. or Tungsten to make it hard. . .
affects the crystalline pattern, with respects to how it cooled and formed up.
And there is distinct visual repeatable evidence of the refractive properties that could be charted.
And she was trying to establish a method of "wrecking the magnet and documenting it's crystal patterns"

All that scientific mumbo-jumbo aside . . . . the blades color goes down thru the molecular level,
and is not necessarily a surface condition.
All metals "rust" or oxidize. . .Aluminum oxidizes into a white surface powder. Bronze oxidizes brown.
The grey rust on the blade is specific to the Iron/steel alloy recipe that the Italian 70 years ago used on the knife.

[Bill DeShivs]

I do see a difference.
The blade was very badly rusted, and someone tried to clean it up. It has been sanded and polished, blurring the crisp lines it once had.

[donnaohler]

I myself thought I had ruined my coricama 11" by cutting limes with it and not cleaning it afterward. The next time I went to use it it looked much like the blade in your pic. I got most of the discoloration off and was only left with a few black spots. My late husband was probably rolling over in his grave.

[jerryk25]

Aaaaagh . . .a coricama mild steel in citric acid. . .
you're gonna have to inspect it every week for at least 10 years.

I wrecked a stainless 11 inch modern tilt bolster stabbing pickles in a pickle jar.
Left it in my camping gear for 2 months.
Didn't hurt the blade, the the brass liners kept growing green fuzz under the tilt bolster..

I also wrecked a few knives power buffing them on a cloth wheel with cutting rouge.
Like Bill said. . .you could see the loss of the crisp line on the center. . . .
I'm older and much wiser now.

[Mario]

I myself thought I had ruined my coricama 11" by cutting limes with it and not cleaning it afterward. The next time I went to use it it looked much like the blade in your pic. I got most of the discoloration off and was only left with a few black spots. My late husband was probably rolling over in his grave.

Best to always clean and oil your blades after using them for food prep. I usually dip them in mineral oil and give them a wipe with a cloth.