Rust Removal.....what works best?

[w30bob]

Hi Guys,

After hearing this weekend about using Muriatic Acid to remove rust from nuts and bolts I gave it try yesterday. I'm not sure why I thought Muriatic acid was weak....but it's not. It's hydrochloric acid. Burns like heck if you get it on your skin and the fumes will suffocate you very quickly. But it sure takes off rust QUICKLY. I'm taking minutes for even heavily rusted things. I'm guessing that if you leave something in it for any length of time that thing will totally disappear. But knowing it works quickly and checking on the parts every minute or so does result in impressive rust removal. I also learned to have plenty of baking soda on hand to neutralize it.

But I went online last night to learn about it a bit more and many were recommending using Phosphoric acid instead. The reason being that when using Muriatic acid the part will immediately start to rust once you pull it out and neutralize it with water and baking soda. With the Phosphoric acid the part will retain a protective black phosphoric coating that will inhibit rust for a time. Sounds like a better deal to me.

I routinely use Evapo-Rust, and sandblast.....but I'm always looking for a better way to do things.

Has anyone used Phosphoric acid to remove rust? Does it work better than Muriatic acid in terms of the part not rusting so quickly when the part is cleaned. Anything else I need to know....other than to wear long sleeves, eye protection, and do it outside? Any thoughts would be appreciated.

thanks,
bob

[monkeymissile]

I plan on trying RustBeeter, sounds far less toxic than most products
http://www.rustbeeter.com/

[52 M-42]

I like media blasting the best. I know it is a mechanical as opposed to a chemical process, but it doesn't poison me, burn me, blind me, suffocate me, or ruin my clothes; and ruining my clothes REALLY gets me in trouble.

However, another good chemical method, is oxalic acid (radiator cleaner) in a plastic dish pan with a battery charger hooked up to it. The weak current "galvanizes" the rust away (it is not fast) and you end up with shiny, clean parts. Watch the water level though, it does evaporate. It's fairly safe, but needs to be done outside.

52 M-42

[w30bob]

Hi MM,

Looks interesting. On the downside it costs about as much as Evapo-Rust, which I do like and use, but gets expensive for large parts. Let me know how that stuff works for you.

Hi 52-M,

I also use a sand blaster frequently...actually it's a glass beader, but it's an industrial unit and does work well. The only thing I don't like about it is the way it leaves the surface of the metal. After blasting the metal is a bright grey color....nothing like what it was when new. I found that if I checked a part I had soaking in Muriatic acid every minute or so I could remove the part before the surface became etched. But the parts rusted in minutes when exposed to the air. The phosphoric acid is claimed to to apply a dark surface to the part that protects from re-rusting.....but not permanently.

thanks guys,
bob

[sturmtyger380]

I like using Phosphoric acid. What I like is that it is easy to find and is not as bad for your skin. It will still burn though. I take parts and soak them in a plastic pail of the stuff. I have also bought heavy plastic paint drop cloths and created a plastic container almost the same size as the object I want to soak. Then fill until I cover the part. If you do it right you might only need a couple of gallons to soak a part. I have a small hand pump that I use to pump out all the acid from the soaking container and put it back in the original containers. Then I use it many times before it slows down.

To clean it off you can use soap and water or you can scrub with Acetone and a rag. Once clean I have had no problems sanding and priming the metal.

Alan

[w30bob]

Hi Alan,

Where do you get your phosphoric acid?

thanks,
bob

[m15256]

I think you want to look up OSPHO. It is phosphoric acid blended as a rust stabilizer and used a lot on boats. Information is available on the internet.

[w30bob]

Thanks Rick.....I'll check it out. I went to Lowes this afternoon and bought some Phosphoric acid. It 's a product called Prep and Prime I think, or something like that. I have some test parts soaking in it right now. Definitely doesn't work anywhere near as fast as Muriatic...but if it gets the rust off and leaves a nice black finish I'll be happy. I'll let you guys know how this turns out. Next thing to try is electrolysis.

regards,
bob

[m37jarhead]

Speaking of rust, the eternal enemy, I've been using a product for 20 years called "Rust-Mort". Claims to stop rust particularly
in areas that cannot otherwise treated for rust. Rust-Mort is 75% phosphoric acid. Other ingredients are chromic acetate,isopropanol, water.
I brush on 2 or 3 thin coats of Rust-Mort then let it dry for 24 hours, then prime and later top coat. Rust-Mort turns red rust to black.
Available at auto paint supply stores. Fairly cheap. One pint is a hundred year supply. Like any acid, use proper precautions when applying.
JB

[w30bob]

Hi Guys,

Well....my experiment with the phosphoric acid didn't go so good. The parts I soaked in it did come out rust-free, but they had a black coating on them....which I thought was a good thing. But immediately when I touched it the black came off all over my hands. I guess if I let the parts air dry before handling them the black coating would dry as well...but it's not a long term rust preventer. Funny thing was I also put a bracket that I had soaked in Muriatic acid in the phosphoric and it turned a copper color. Weird. But that copper color came right off in my hands as well.

I guess what I'm really looking for is a rust remover that also applies a hard coating on the part.......but I guess I'm asking for something that doesn't exist. I read recently about something called a "zinc wash" to apply to parts that have been de-rusted. I'll look into that. I'm also going to hit a marine supply store this weekend to get some OSPHO, if I can, and give that a try. If that don't work I'll stick with the Muriatic for immediate results, the Evapo Rust for the more delicate metal parts, and sandblasting for the bigger stuff. And I will be trying electrolysis soon. But keep the ideas coming if you have them.

thanks,
bob

[Sal]

This might be of some help if your going to try elctrolytics. READ THE WARNING ABOUT THE USE OF STAINLESS STEEL .

http://www.stovebolt.com/techtips/rust/ ... usting.htm

Sal

[w30bob]

Sal,

That's a great link....thanks!! I also found out today that OSPHO seems to be back ordered nationwide. Must be some popular stuff.

regards,
bob