My buddy used it to get the rust off of his nuts and bolts, would it work on my brake drums without messing them up?
I use muriatic acid to clean small parts, or anything that fits in a bucket. It definitely will take care of the rust. But, i would etch the machined surface, & you would probably have to get them turned again
I used citric acid on drums and lots of other rusty parts. Muriatic acid is nasty stuff, you need to cut it with water. For swimming pool filter de-crusting, I use a 1/2 gallon of acid to 5 gallons of water. And remember from your chemistry 101... AAA, always add acid. Never the other way around.
As mentioned muriatic is nasty stuff, it will soak into the porosity of the cast iron drums and will be difficult to rinse and neutralize. Even if you think you have them clean and dry the acid will leach out of the pores and cause them to rust. I would sandblast them.
What he said, use Evaporust. I had a Morris Mini dipped by a commercial firm near Ann Arbor MI back in 1995. By 2000 even with them "neutralizing" the acid (I think it was a solution containing muriatic acid) the British water soluble steel was disappearing again, even with a good effort at sealing and painting.
I just cleaned up a pair of brake drums with a wire wheel on my grinder. Have done it with a wire brush too. It’s not a lot of work.
If you open a bottle of concentrated Muriatic aka Hydrochloric acid indoors, the fumes will drift around and whatever steel or iron tools etc. they encounter will get a brown layer of rust on them. At least that's how I ruin my tools.
I'm not sure if cast iron is susceptible to hydrogen embrittlement or not, but be careful putting acids on iron and steel components that your life might depend on. That said, I have used oxalic acid with success on cast iron. You could always get them tanked at your local engine rebuilder. Blasting is probably the best option.
Hydrogen embrittlement (HE) is an issue on hardened steels. Generally Rockwell C of 30 and higher is considered the susceptible range. Brake drums are not heat treated, but springs, bearing surfaces, and some fasteners are examples of parts that should not be processed in acid solution.
Muriatic Acid. It's great for concrete. Muriatic aka Hydrochloric Hydro... Chloric.... Muriatic acid can chlorinate the steel. Chloric....Chlorinate....Chlorine!!!! You see, I hard to learn this the hard way. I even researched it but.... Ain't it funny how when you research something all you find out is how great it is. Then after you actually do it, all you find out is what a bad idea it was. Yeah, I know it does great on a nut. The Harley guys swear by it. All I can say is anything I used it on went bye bye. Yes I did flush, probably the equivalent of Lake Michigan. Yes I did use baking soda. If it chlorinates the steel, it's not on the steel but in it.....It's kind of like a cannon that's been in the ocean for 300 years. The salt is in it, not on it. Use at your own risk.
Acids have H+ ions, it is what is definition of an acid. An HE fracture is intergranular. Fatigue cracking or overload is transgranular. If you look at HE fracture surface under magnification, it looks like rock candy, or a faceted type appearance. HE also requires a sustained tensile load. It won't happen on a part not being stressed. HE failure also happens within few hours to 72 hours. Back to the OP question, any acid can remove rust (iron oxide). Weaker acid is easier to control the rate and the general safety. Any acid process needs a neutralizing in addition to good rinse. The fresh clean metal surface will rust very easily, so some protection is recommended.
as Mr Beanscoot said, a bottle in your shop, even with the top on will rust everything for about 10 feet away. I used to use it, its very fast, but there are better methods today
Evapo-rust isn't the cheapest thing but if you put the drum or parts in a plastic pan that it just fits in and pour the evapo-rust in on it until it covers it up and let it sit it does a hell of a good job on rusty items and leaves a black oxide finish on them. Second photo is a rusty log chain I had laying around that I put in the Evapo-Rust. Bottom shot is from a couple of days later after I remembered to take it out.
I've cleaned rust off brake drums with Molasses mixed 1 part molasses to 4 parts water. Takes a few days but did not "eat" the parts like vinegar does. Hose it off and paint/primer before it flash-rusts again.
It might be better to use phosphoric acid products such as “ Deoxi Does It”, rather than muratic acid. After a through soak, 12-24 hours, most parts are pretty clean, if not scrub and soak again. A final soak will create an iron phosphate surface which does not get rusted again easily. Works for me.
A safe, effective, and cheap way to remove rust is to use white vinegar. Let it soak a day or two and neutralize with baking soda and water. You can neutralize the vinegar with baking soda, or use it to make weed killer
Phosphoric acid based Rust removers/ metal prep are the fastest most effective way to treat metal ,sandblasted surfaces should be treated before priming .Chelation technology takes longer to remove the rust and will re rust in a short period of time. It is safer than an acid very similar to the situation with methylene chloride paint remover. Rust remover that are 30/ 35% concentration phosphoric acid , with surfactants and wetting agents and zinc oxide powder removes the rust quickly and prevent its return. Panels treated with this phosphate solution can be stored indoors for up to a year without rear rusting It improves welding conductivity and adds additional Corrosion Protection to your paint work.
The big problem with Muriatic acid is that it is more than a bit hazardous to use even when you use it for it's intended purpose and disposal has to be done right. The Evapo-Rust is bio degradable but I'd say most of us just pour it back in the jug and save it for next time and go again until it looses it's strength. No issues as far as getting it on your skin as far as getting it on my skin either unlike Muriatic acid that is going to cause some chemical burns.
I only use it outside when I de-gunk my DE pool filter guts, even citric acid solutions I leave outside loosely covered.
I hope you mask the area where they will be cut when they are turned. If you don't the sand will stay in the surface and dull the tooling quickly when they are turned. Charlie Stephens
Some of the vintage bikes I mess with have chrome plated cast iron brake rotors..The chrome starts to peel.removing it give better braking. I put a rotor in a plastic container and use full strength muriatic or what strength they sell retail. Let the rotor soak for 1/2 hour or so...All safety precautions in place and it's done outside.I dilute the waste acid and pour in into shop sink were it goes into the septic... Muriatic or phosphoric acid is sold in hardware stores for cleaning drains...That the kind I use...
Had muriatic acid in the garage one winter. Ran the old kerosene heater. Caused some terrible fumes. Also left tiny rust specs on the stainless of my 54
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