I’ve used many different types of rust removers in my somewhat futile effort to keep old clunkers on the road. Ospho is okay on metal but not so good on aluminum, cider vinegar is great but very slow working and is acidic but the best one I’ve found is Evapo-Rust.
This fairly large container of Evapo-Rust can be bought online for less per ounce than the local big-box stores. If the stuff weren’t so expensive I’d use it to clean the inside of rusty gas tanks. As it is I can buy a new gas tank for about twice the cost of enough Evapo-Rust to fill the old, rusty tank
I’ve soaked zinc carburetor bodies in Evapo-Rust for a week without eating the soft base material. Rubber parts seem unaffected after a bath in Evapo-Rust. I don’t think it will eat carburetors ever but I haven’t tried it as long as ever. Evapo-Rust cleans the gooey carb residue along with the powdery zinc corrosion equally well. The brass carb parts come out looking like new. I haven’t found any metal the Evapo-Rust won’t clean. I’m sold on the stuff for carbs.
Evapo-Rust is great for chrome or zinc plated nuts and bolts and all the little doo-dads that need de-rusting during a motorcycle restoration. One example is the chrome headlight fork ears on the old Kawasaki 900. They were lightly rusted between the folded parts of the ears and there was no way to get down in there to clean them. A few days soaking in Evapo-Rust saw them nice and clean. After washing the parts with water I give them a shot of oil and they haven’t re-rusted. (Note: I live in New Mexico so rust is not much of a problem out here.)
Like most things in life there are a couple catches: You want to avoid leaving parts in an uncovered container of Evapo-Rust for a month like I did. The Evapo-Rust evaporates down into a thick, dark, almost plastic mass that glues itself to your part and the container. It’s a real chore to pull the part out of the container. The freebased Evapo-Rust is the consistency of really strong taffy candy. That gunk is harder to get off than the original rust! Check your parts every week or so and seal the lid if you can.
Evapo-Rust does not work as well on parts too large to submerge. I tried it on some rusty corrugated roof panels. Following Evapo-Rust instructions I soaked rags with the product and laid the wet rags on the rusty spots. Then I covered the rags with a large sheet of plastic to keep the area moist. After a couple days the rags were stuck to the roofing. I used water and elbow grease to pull the rags off. The rust was somewhat cleaned up but I think regular Ospho works better on large surfaces.
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