VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1912-1928 Rust removal with muriatic acid

Has anyone tried using muriatic acid for rust removal? I just cleaned up my front fenders with it yesterday and today. These fenders were in pretty bad shape. The inside was pitted and the outside was painted over rust patina. After removing the paint with paint remover and a wire brush, I tried sanding off the rust. It was pretty tough going so decided to try mauriatic acid. I kept on brushing on muriatic acid and all the rust came off in about any hour. It would probably take less time if it was warmer - it was close to freezing. It even cleans out all the pits.
This is a job you need to do outside because of the fumes and you do have to protect yourself with gloves and goggles at minimum. When the metal was clean I rinsed it well and neutalized it with a baking soda solution. I then dried it and coated it with Rust Check because if you don't it will flash really quickly. Here are some pictures. The first one is the second fender ready to start. The second and third are the cleaned fender. The black is original paint. For some reason paint remover won't touch the black paint they used on fenders back then. The patch panels I made and welded in last year to fix some really ugly repairs some previous owner made and some rot.

Hey Arend
Is your fender a two piece, spot welded together at factory?
If so take extra measures to clean/ neutralize where the two metals over lap/welded to each other (very hard area to clean).
A friend of mine used acid to clean his fenders a few years back (don't remember what kind) but didn't neutralize /clean this lap jiont good enough, when he washes the car he would have rust/acid leach out onto his nice paint job, which is starting to oxidize the paint in those area's.
This might also start to thin the metal joint haveing acid/rust build up in this joint over a period of time.
If you are going to use acid, try not to let it leach into this joint so you don't get acid deposit build up .
I hope this tip will help with your cleaning.
It may be a lot less work to load up your parts that need to be cleaned, and take them to a self sandblasting place like Consolidated Sand Blasting , and blast them your self, I think it was $85.00 an hour and they supply all materials, you just have to do the work, you can get alot of pieces done in a short period of time.



Keeping vintage Chevy alive.

Anyone using muriatic acid should use protective equipment. First a respirator or gas mask to protect your lungs. Second a face shield and safety glasses (yes both) to protect your face and eyes. Then long rubber gloves and a rubber apron to protect your body. And before using any chemical get and read a copy of the Material Data Safety Sheet (MSDS). It contains valuable information on all aspects of handling hazardous chemicals including use and disposal. Muriatic acid is concentrated hydrochloric acid and can quickly damage skin, clothing, etc. If you don't feel completely comfortable handling any chemical don't! Leave it to the experts to use them.

Muriatic acid can be an effective rust removal chemical. It quickly dissolves most forms of rust (iron oxides). The process can generate heat and gas so be aware that it can bubble, foam and possibly result in some material ejected from the surface.

It is best to try it in a small area first to see what happens before using it on a large area. Also it will not work well if the material being cleaned has grease or oil on the surface.

When muriatic acid is used it is necessary to consider disposal of the spent acid, rinse water and neutralizing agent. Being a hazardous chemical there are specific approved methods and failure to adhere to them can result in environmental damage and a stiff fine/and or jail time.

If after reading this you still want to use muriatic acid it will work under the right conditions and can provide an excellent surface for paint. It must be neutralized relatively quickly or rerusting will quickly occur. Rinsing with clean water (rinse water also a hazardous waste) followed by baking soda solution will work okay but passivating the metal with a stronger base is better (though more difficult to do safely).

Another thing to be aware of is acids EAT aluminum, zinc, pot metal and similar metals.

Do I use muriatic acid? Yes but not to derust fenders. It is used in the swimming pool and to clean engine cooling systems. That has been discussed previously on ChatII. I also have a degree in Chemistry and worked for 31 years for a major chemical company so have knowledge and training for the handling of hazardous chemicals.

Good tip. Thanks.

I like to use Phosphoric acid. Have had good luck with it and you should see how nice it cleans brass carbs! Will make them look like brand new with out removing detail like bead blasting will. It will also attack zinc and pot metal so be aware of that. I cover the areas with rags soaked in the dilluted acid for sheet metal and keep them wet. For heavy iron items I just dunk them in a plastic tub and the same for carbs. I have been using the metal prep from DuPont which is Phosphoric acid. As for the paint, if the original paint was enamel and I belive it was Duco Enamel by DuPont, then Lacquer thinner will bubble it up nicely. Rags soaked in thinner work great here also. Just let them sit and do their stuff.

Phosphoric acid is a better option in several aspects. It is not as aggressive as muriatic or hydrochloric. It is much harder to obtain and safer to use. It also leaves a much better surface for recoating or paint. The dilute versions like the metal conditioners (also contain other chemicals) are relatively easy to find but much more expensive. I use a phosphoric acid based metal conditioner on a daily basis for small parts including brass parts as BK suggested.