Happy New Year, everyone. Are there any practical ways to remove rust stains / spots from a plastic stock without repainting or refinishing somehow? This is an FN A2 stock, but I figured the retro crowd probably has a lot of experience with this on surplus parts. I found a method online for using a vinegar and baking soda paste to soak and then scrub the rust. It took off the surface rust but also buffed the plastic a little more white and left the embedded rust spots. It looks like the rust penetrated into the plastic surface a bit, so I'm guessing this is something I just have to live with.

This stock is intended for an older A2 clone that doesn't need to look pristine, but I suspect the rust spots are from storage and not something that was there when the original rifle was in service. I bought a second surplus stock with this one that is in better condition and darker, so it hides the spots better, but it has a stain in roughly the same location, so I'm guessing they were all stacked in a box for a while and developed these spots. I will probably just give this stock a wipe down with some Slip2000 since it's pretty dry. I figure that will even out the appearance, protect the plastic, and conceal some of these blemishes a little better. Thanks for any advice you all can offer!

Attached File

You need stronger acid, and you need to avoid baking soda and other abrasives. No scrubbing.

Try phosphoric acid or "naval jelly." Test it first on the inside or other inconspicuous area of the stock.

You may be able to restore the texture of the area you polished with the right combination of sand paper or similar.

I would try Mothers Mag Polish.

Thanks for the feedback. Is it possible that removing the rust with something like naval jelly will leave a cavity in the surface of the plastic? I.e. has the rust displaced some of the plastic? I'll test it first on the inside surface that's covered by the buttplate, as you recommended. I think I'd prefer to live with the stains rather than end up with pitting or an indentation on the surface.

Edit: I just read a couple reviews that said that naval jelly is not recommended for use on nonferrous materials such as plastic. I found this article on Bob Vila's website that lists Evapo-Rust and CLR PRO Calcium, Lime & Rust Remover as safe on plastics:

The Best Rust Removers for Household Use

Sounds like Evapo-Rust might be one to try: "It’s also safe to use on non-rusty steel, plastics, PVC, cast iron cookware, toys, and most painted surfaces that may be in contact with rusty metal hardware."

The CLR Pro Cleaner section says "The formula utilizes both lactic and gluconic acids, which are less caustic but no less effective than harsher acid-based removers. It works wonders on rusty tools, outdoor equipment, car parts, stainless steel, plastic, ceramic tile, glass, and fiberglass surfaces and is also a great alternative to ammonia- and bleach-based products on hard water deposits, soap scum, and rusted toilets."

I'll look into those two options. Not sure how I missed that article the first time around.

Thanks for the tip, I picked up a bottle at O'Reilly Auto Parts. It's definitely not cheap, but I was anxious to keep working on this. It's definitely taking the rust off, but it's very slow process. I may be doing it wrong... This is what it looks like after about a dozen applications. The spot off to the right is almost gone, but the two in the middle are pretty stubborn. It's still turning purple, indicating that it's pulling iron out of the plastic, but the rust must be pretty penetrated the plastic pretty well. I noticed that it whitens the plastic a little where the liquid sat (not much after one application, but it seems to accumulate. I'm guessing it's just drying out the plastic a little, and apply some oil when I'm done will blend it back in. It was more noticeable on the darker stock that's in better condition, which has one distinct rust spot. I may eventually quit while I'm ahead and use some oil to treat them both, to make sure I don't take it too far and bleach the plastic in these spots more than it already is. Here's how it looks now:

Attached File

TRY THIS

Thanks, I think I'll try Evapo-Rust for some of the smaller components, like the butt plate that has a pretty solid coating on the small metal tab that the trap door latch engages. I believe you're supposed to immerse the parts in Evapo-Rust and let it soak for 24 hours, which I'm not sure I want to do with the stock right before testing it on other things. The Meguiars liquid clay didn't work very quickly on the small tab on the butt plate. I think it may need a more prolonged soak.

I've used a polish called Never Dull on rust stained glass and aluminum and chrome plated wheels and bumpers.  Removes the rust/rust stains easily.  Never Dull has removed rust on blued magazines easily, too.

Never tried it on plastic/polymer.

Try a bit of Evaporust. Gel would probably be best for this.

Thanks, it looks like my local Home Depot has the gel, so I'll pick some up this week. I hit the point of diminishing returns after about two dozen treatments with the Meguiars liquid clay. It seemed be lightening it ever so slightly each time, but not enough to make it worth the trouble. I decided to give it a light coat of Slip2000, and it conceals the spot pretty well, as well as refreshing the plastic. Here are the latest before and after shots. I'll try the gel on the other stock I have, which is much darker and cleaner looking, but has a very distinct rust spot in about the same location.

Attached File

Attached File

Attached File

Attached File