So, I shot my P226 the other day. It’s about 10 years old and has about 10,000 rounds through it.

After the range, I broke the gun down to clean and I notice a small slivery white blotch about an inch up in the magwell on the backstrap side of the magwell. Initially, I did not think much about it and started to clean it with a regular bristle brush and some clp. It did not clean off so out came the opti-visor and flash light for a closer examination.

It’s clearly a bit of corrosion that ate down through the anodizing and into the aluminum of the frame. I have no idea what could have caused this as I take very good care of my firearms. As its purely cosmetic, I did not freak out. I scrubbed it off as best I could and touched it up with some aluminum black.

However, out of an abundance of caution I started to check the rest of my collection. Sure as hell, my other P226, which is a Legion with very few rounds through it, has two small spots of corrosion in almost the exact same spot inside the magwell! No other guns in my safe seem to be affected.

Needless to say, I started to wipe everything down paying extra attention to lube the magwells in the pistols with either steel of aluminum frames.

My safe is in a bed room in a dry environment.

Any idea what could have caused this?

Hot day. Sweaty hands. Mag changes. Sweat got inside the mag well. Not a place you normally think about.

That’s all I’ve got.

Get a Golden Rod for you safe.....it might be dry in the room, but any humidity inside is trapped.

Is there anything odd about the magazines at that same spot?
Neither the sweaty hands or humid safe environment explanation seems credible to me. Why would either affect just that one spot, and especially inside the magazine well? Also, why would they affect only those two guns?

If the magazines had the old zipper or dovetail back seam I’d wonder if something was going on with the weld or if some sort of contaminant had gotten lodged in the seam. I assume, though, that the magazines don’t have welded seams at the back—?

Even though the two guns are somewhat different models and age, perhaps it was just an artifact of the manufacturing process that carried over to different times.

Added: Do you leave magazines in the well in storage?

quote:

Originally posted by sigfreund:
Is there anything odd about the magazines at that same spot?
Neither the sweaty hands or humid safe environment explanation seems credible to me. Why would either affect just that one spot, and especially inside the magazine well? Also, why would they affect only those two guns?

If the magazines had the old zipper or dovetail back seam I’d wonder if something was going on with the weld or if some sort of contaminant had gotten lodged in the seam. I assume, though, that the magazines don’t have welded seams at the back—?

Even though the two guns are somewhat different models and age, perhaps it was just an artifact of the manufacturing process that carried over to different times.

Added: Do you leave magazines in the well in storage?

I checked all my 226 mags. No burrs or marks that match where the corrosion spots are in the magwells.
What is so odd about this is that the corrosion is only in my P226s and almost the same spots. None of my other firearms are affected. I do not leave mags in either gun. However, I am starting to think it is mag related because I do use the same mags in both guns and the problem has not affected my third classic series Sig, a P239 which is pristine and of course uses different mags.

quote:

Originally posted by photohause:
Get a Golden Rod for you safe.....it might be dry in the room, but any humidity inside is trapped.

Thats good advice but I don't think its humidity related as none of my blued steel guns are affected. The spots look like some kind of chemical corrosion the way it ate through the anodizing down to the base aluminum.

Any wear point at which surface protection has been compromised, can corrode. Aluminum oxidizes easily; the oxidation forms a protective layer on the aluminum. To prevent corrosion, you can alodine, or chemically treat the aluminum, then cover it in a paint or other surface coating. Alodine will not reduce wear, just corrosion.

The area may also be wiped with corrosion x, or other similar inhibitors, to prevent further corrosion.

Often one type of corrosion is leads to, or supports another. Fretting corrosion, which is friction or two parts rubbing or chattering, can penetrate a protective surface, leading to other kinds of corrosion.

Corrosion on aluminum can also form beneath protected surfaces. exfoliation will show up and a raised surface under paint or other coatings, and intergrannular corrosion occurs between the grains as a kind of crystaline separation or breakdown of the metal structure; it's usually related to improper heat treatment or a poor alloy, and occurs inside the metal, rather than on the surface.

Galvanic corrosion, from the sounds of it. Steel--especially stainless steel which SIG likes to use for its slides over the last couple of decades or so--doesn't play nice with aluminum, regardless if it's been anodized or not. All that's needed is a bit of moisture and that can certainly come in the form of humidity if the storage means was left unmonitored over a period of time. Or if a gun has unknowingly been put away wet to the point where the moisture can bridge across from the steel to the weaker aluminum and allowing electrolytic erosion to occur. I used to see this at times in the construction world on buildings of a certain 'cheapness', where the window contractor/designer/Joe-Blow-the-handy-dandy-man was careless with what he was butting his aluminum storefront or window system up against, without properly maintaining some sort of isolating barrier like a caulk joint to help prevent this sort of aluminum erosion from occurring.

Hopefully the damage in your case hasn't progressed too far into the aluminum alloy.

That is weird. After being responsible for fleets of training P228s and P229s, and having my own innumerable P-series, I've never experienced such a thing.

I picked up an otherwise as-new P226 in .40 from CDNN in DEC last year. Redbox and refurbished version, and absolutely looks like new except for the mag well. Not a big deal to me, but the back interior of the MW is missing a lot of finish. I don’t know why the re-anodizing didn’t take on the inside of the MW. I just keep a magazine in it so I don’t see the Uglies

I think I have a wear spot in the exact same place on my P226s. It's almost looks to be from quick mag changes where the mag isn't inserted completely straight, which is normal. I've never considered it to be from corrosion.

quote:

Originally posted by DansSIGs:
OP,
The corrosion came about from the anodizing process as to where the electrode contacted the frame.

Only witnessed on certain P226's & certain P229's in my possession.

Fault of going to the cheapest bidder to accomplish the task.

This makes sense, especially in my Legion, where the spots of corrosion have a uniform squarish shape.

quote:

Originally posted by flesheatingvirus:
I think I have a wear spot in the exact same place on my P226s. It's almost looks to be from quick mag changes where the mag isn't inserted completely straight, which is normal. I've never considered it to be from corrosion.

Definitely not rub or wear marks. Also the spots are a bit higher into the magwell than where the top of the mag would hit during a mag change.

I had a similar issue and sent it back to Sig. They sent me a new pistol with apologies. YMMV.