[NBF823]

I have some suspension parts that PA salt magically bonded together, so I'm soaking them in vinegar. I've never done this before, and this is day 1. Should I add salt, baking soda, nothing, or some other unmentioned ingredient?

[lilabner]

Evapo-Rust
Works better than great..

[NBF823]

I actually tried that with a caliper last year. I didn't like the results - mostly just black. After a few days, still couldn't remove piston, just got new rock auto caliper, which less economically viable in the current attempt. Granted, the caliper was crazy rusted. Thanks though. Might try the Evapo-rust again.

[lugnutx2]

I soaked TP air cleaner screens in straight vinegar for 2 days and they came out looking new.

[John V.]

Vinegar is a mild acid. Adding salt (sodium chloride) does something chemically (I'm not a chemist) that improves the process.

Baking soda is caustic.

You use it AFTER the acid dip to neutralize. You need to do this to stop the acid from continuing to eat the metal once the rust is removed.

The vinegar bath works best for disassembled parts.

Not sure it will work as well if the problem is rusty bolts that you can't remove to separate parts.

Other acids like hydrochloric (muriatic acid) can also derust parts but different chemistry is involved and you have to be careful you aren't dissolving the iron altogether.

Adding salt puts chloride ions into the vinegar mix but because the acetic acid is not as strong as hydrochloric, the process is slower and less likely to dissolve the "good" iron.

That is my layman's take on the subject.

If you are trying to get some rusty bolts loose, I'd be inclined to use penetrating oil, heat, and vibration. Once apart, then derust the parts.

If the parts are "glued" together by rust, let 'em soak and see what happens.

Evapo-Rust works by a different chemical process and won't attack the good iron like an acid will.

But I think it also is best at removing the rust on the surface once the parts are disassembled.

[melemans]

I started out using straight vinegar to remove rust and found that if I left the part in the solution too long it would pit the metal. So, I now dilute the vinegar with water and am very pleased with the results.

[george kujanski]

Mild acids will derust mild rust such as surface rust. I used to use Dupont Metal-Prep for prepping metal for paint...it's phosphoric acid..did a nice job on surface rust but does work slowly, and it will bite your skin.

George