Stainless corrosion

[Standing Wolf]

My new (to me) Python is definitely a shooter, and has a pretty good trigger, too. I field-stripped it for cleaning over the week end, and noticed a few spots of dark grey, almost black color where the crane and frame intersect. I thought at first it might be old oil and/or Cosmoline, but it couldn't be scrubbed off, and solvents didn't touch it, so I'm assuming it's a thin layer of corrosion.

What should I do? I have to confess I'm nearly completely ignorant when it comes to stainless steel.

Thanks, eh?

 

[P95Carry]

Hey SW ... if black then not sure if that is ferrous corrosion per se. depending on chrome/steel mix .. S/S can permit a low grade rust but - not sure it'd be actually black. In the area you describe I'm not sure I'd be over fussed ..... but would try and ensure a film of lube or Rig grease etc .. to keep it protected.

I do know that it is possible to ''encourage'' a sorta ''false rust'' on S/S by using fine steel wool ... small particles persisting and themselves rusting ..... as if they have been ''impregnated'' into the S/S ........ tho hardly the case here.

So - bottom line .. not thinking hetre this is ''rust'' per se ..... but a degree of some sorta corrosion could occur ..... forget the chemistry with S/S but - very unlikely to be anything to worry about.

My SP ... carry piece .... gets very sweaty at times and occasionally has slight discoloration but minimal ... and removeable with a fine wipe from Scotch pad type stuff.

OK - not awefully helpful - more ''thinkin out loud''.

 

[dfariswheel]

What you're seeing is quite common on stainless Colt revolvers.
I have it on both my stainless Pythons, and I've seen it on many other stainless Colt's

I believe it's either a left over from heat treating, or a left over of a chemical "Passivating" process.

In any case it isn't corrosion, just a discoloration found in some out of the way places, strangely usually around the crane area.

Short of polishing the metal, you can't remove the discoloration, and since you really can't see it, I'd just leave it be.

 

[stans]

When stainless rusts it is usually an orange color as is any iron oxide. The big difference with stainless is that it usually will not pit like carbon steel.

 

[JNewell]

Without disagreeing at all with dfarriswheel's post, I had a Python that sat for a long while in the safe and during that period the lube inside turned to varnish. (The lockwork was actually frozen in place.) When cleaned, there was some residual discloration on the surface of the metal that sounded very similar to what' you're seeing. If that's what it is, I wouldn't worry. Whatever's left after you've cleaned it isn't going to affect anything. I think it's unlikely that what you're describing is in fact corrosion.

 

[mete]

Lube turned to varnish ? What did you use 3in1 oil? A proper gun oil has antioxidants which prevent oxidation which causes the oil to turn to varnish.....Stainless steel ,to reduce rust problems should be ' passivated' which is a treatment done usually with nitric acid. It removes foreign material from the surface and builds up the protective oxide layer on the surface. Material such as carbon steel particles on the surface can rust and that rust will then continue into the stainless steel....What you saw on the gun was probably scale or oxide from heat treating ,that would be dark grey and difficult to remove.

 

[JNewell]

Not 3-in-1 oil, that gun (2, actually, a Python and a King Cobra) were exclusively lubed with CLP.

What I saw was not process-related effects, it was lube turned to gum. It hadn't been present before, and it was located in areas where parts were adjacent to the frame.

Both revolvers were actually frozen and had to be soaked in solvent before disassembly.

 

[dfariswheel]

Many, if not most older lubes can and will turn to "varnish"
This includes CLP Breakfree.

Years ago, a National Guard tanker gave me a sample of CLP that had just been issued for use in firearms, including the cleaning of their tank's main 105mm gun barrel.

I used this early CLP to preserve a Colt Detective Special for storage.
A year late, the CLP had "varnished" into a sticky, gummy layer in tightly fitted areas.

Varnished lubes invariably have a yellowish color and appear as an obvious sticky-to-dried layer, which is easily removed with solvent.

Again, I have two 1980's Colt stainless Pythons, both with the stain in the crane area.

Again, I've seen this discoloration on many Stainless Colt revolvers of this era with the stain typically appearing around the crane area of the frame, the underside of the ejector, and the rear face of the cylinder in the ejector recess.

In appearance, this stain runs from a mottled thin gray-black to black color. It's as smooth as the surrounding metal, with NO roughness or "crusty" texture.

It appears as "in the metal" stain, NOT corrosion.

For some reason, this discoloration is prevalent on Colt stainless revolvers of the 1980 period.
I have rarely seen it on other makes of stainless firearms, and, of course, never on a blued firearm.

My experience is, this discoloration is a Colt stainless revolver phenomenon, of the 1980s period.
Whatever it is, it ISN'T corrosion or lube varnish. It is removable ONLY by polishing the metal.

 

[JNewell]

For the record and consistent with dfariswheel's post, both these Colts were mid-80s vintage stainless. Location could be a coincidence, though it did appear on the frame and sideplate interior surfaces adjacent to the lockwork (as well as other places).

I suppose it may have something to do with the exact composition of the SS used by Colt in that period. (?)

 

[dfariswheel]

Although the "usual" places for this discoloration to appear is the crane area and the undersides of the ejector and cylinder, I also saw it inside around the side plate area.

Again, my best guess is some kind of chemical treatment or heat treating discoloration not completely removed.

Since it has no effect on the gun, and isn't usually visible to the customer, I just left it alone.

On my two stainless Python's I left it alone, and there's been no change or problems since I bought them in the 80's.

A Colt mystery.

 

[mete]

Any lube that turns to varnish in a year should never be used on guns . My guns are coated with RIG for storage and I usually use turbine oil [ highly refined with antioxidents] and RIG for normal use.I have NEVER had these lubes turn to varnish even after years of storage !!!