Rusty park light lenses...

[Bob Ritter]

Getting the rust stains out the parking light lenses is really easy if you use muriatic acid, this is the same acid that you use in your swimming pool. I have been using muriatic acid on metal parts to remove rust for years, but you need to be careful when using it, follow the instructions.

[Plymouthy Adams]

use of phosphoric does the same thing....with a couple exceptional benefits....it does not harm good steel as it reacts with oxide only and the stuff is a lot safer for the user to handle...it comes in a plastic container so we know it will not harm that.....lol

[Los_Control]

Acid is really cool, learned that when I was 16 years old ....

 

While messing with my truck, sandblasting is not a option. So I have been playing with different acids to help me with it @Plymouthy Adams has helped me a lot with my journey using acid to remove rust.

I have learned that their is a time and place for different acids.

 

Here is a image showing what muriatic acid can do for a rusty fender. Look at my thumbnail image for what I started with, then the results.

It works great, but will instantly start to flash rust if not neutralized properly.

If used in the garage in a small bowl on the bench, fumes will flash rust your tools and other metal parts within 10' of the small bowl. While using it on your vehicle, it will flash rust parts you never touched. .... Choke, throttle cables, hinges etc...  I used it on a headlight switch once and it melted the pot metal ... Thanks to another member here that helped me with that.  I use muriatic only with metal on saw horses in the back yard and far away from everything else. And it is killer on the lungs if you breathe it in.

 

Ospho is a good acid also, not as strong as the muriatic ... it has a special feature where it just turns rust into a paintable black primer .... spray it on your rusty undercariage and later paint it ... is all lumpy & bumpy, but it has it's place to be used. But it kills the rust and a great place to use it is inside of doors where you cant reach. Just spray it in and will neutralize the rust, keep it from spreading. I would also use it on metal fence or buildings before painting ... not a prime automotive finish.

 

Phosphoric acid I think is the key ingredient to all of them.  A gallon of 85% phosphoric is close to $50 plus shipping.  Is also food grade and used in restaurants to clean rusty stainless steel appliances. Here is a photo with 85% phosphoric acid on the bed of my truck ... it looks terrible. The white stains & stripes is actually the 85% phosphoric acid protecting the bare metal from rust, while the rusty areas is where the acid was thin and washed off. A pressure washer actually removes it nicely, but until ready for paint am better off to leave it alone.

And next time I will dilute the acid with water before applying. ... For giggles I poured some in my toilette. I have a high end tall boy elongated toilette in my bathroom ... house has hard water and sat for sale for 2 years.  I poured a 1/2 cup of phosphoric acid in it, let it sit for 20 min and cleaned the toilette ... looks like brand new. The hard water stains just washed away.

 

The acids all have a use ... I would be careful suggesting one over another. ... They all have their pitfalls also.

[knuckleharley]

I haven't tried it,but I suspect vinegar would work fine,too.

 

It does a fine job of eating rust on steel.

Edited June 28, 2021 by knuckleharley

[Dan Hiebert]

Only problem with acids is that they all can dissolve steel, which is why they are stored in plastic or glass.  But they'll eat rust first.  A good friend (a chemist) taught me about them many years ago when I was cleaning up the '60 Ford F-100 we used to have.  I've forgotten a lot of what he told me, so I've erred on the side of caution and haven't ventured down that path lately.  Good cleaning solutions, but you have to pay attention to what you're doing and neutralize the surface(s) once you achieve your desired results.  You can't just plunk a part in a bucket of acid and leave it.  Readily available too.  Phosphoric acid is the main ingredient in drain cleaners, so you can de-rust your parts with Drano.  

[westaus29]

Los_Control you give a good summary of how to use muriatic acid. It is also good for cleaning bore stains off paths and brickwork, but is better diluted with an equal quantity of water. Concentrated 85% phosphoric acid is nasty stuff. I have researched it and dilute it to 20% strength and add a small amount of dish washing detergent. It gives a stable grey coating to bare metal and I believe it was used by Chrysler to prepare panels for painting, as have seen the same finish when stripping paint from my panels. It can also be purchased from hardware or auto stores in diluted form labelled as a rust remover, with a price markup of about 1000%, which is why I make my own.