Gas can repair

[Kevin B.]

I have three 5 gallon cans I got from Rick that I'd like to bring back to life. They don't have any leaks, but they were full of rust and crap until I hosed them out. One even has something oily in it. What's the best way to clean these up before I hit them with a sealer, would a mild acid do the trick?

 

[Kevin B.]

I'm finding muriatic acid or sulferic acid is supposed to do the trick. I did not know rust was a base, so that's cool. I think I have some sulferic acid in the cupboard, so I'll give that a try first. I'm not seeing any specific concentrations, so I'll experiment unless somebody knows? I'm also wondering how the diesel oil or whatever is in the one can will affect the acid. One way to find out, I guess.

edit - called my favorite rad shop, they want $75 a can to clean them. That's nuts. I've got one soaking in a mild acid bath right now, I hope it works.

 

[sawtooth4x4]

Ace sells muriatic acid. Its about $4 per quart. I used some to clean all the oil stains from my Ford off the driveway. Its pretty powerful stuff, do not get it on yourself. It'll hurt and burn like hell.

 

[I Lean]

You can get Muriatic Acid from Lowe's as well...something like $7-$8 per gallon. Diluted 50/50 with water, it's still pretty powerful. (but it might be already diluted in the bottle, so check that)

 

[thefirstzukman]

Throw in a couple cups of Muratic Acid and a bunch of multiple size nuts/bolt or whatever in the can (nothing too heavy) screw the cap on and shake it like a baby.. do it a couple of times, while soaking it in between with a diluted acid water... I used to restore old metal gas tanks for atv's , it works pretty good. Muratic acid can be found pretty cheap at any masonry supply store or homedepot

 

[Kevin B.]

Throw in a couple cups of Muratic Acid and a bunch of multiple size nuts/bolt or whatever in the can (nothing too heavy) screw the cap on and shake it like a baby.. do it a couple of times, while soaking it in between with a diluted acid water... I used to restore old metal gas tanks for atv's , it works pretty good. Muratic acid can be found pretty cheap at any masonry supply store or homedepot

The nuts are to knock the rust off?

 

[AaronPaige]

Yep, or steel shot anything to help scrub the inside of the tank...

 

[MikeGyver]

Muriatic acid eats rust like mad, It's what you want to use. If you put nuts and bolts in be aware the zinc coating will dissolve very quickly and buildup pressure, so don't seal the tank at least until the fuming has come down.

 

[mesha]

Add a bunch of muriatic acid and a bunch of zinc shavings. seal, shake, and run.

 

[Kevin B.]

Add a bunch of muriatic acid and a bunch of zinc shavings. seal, shake, and run.

I think I need an unthankyou button.

I let the least rusted can sit overnight with a mild sulfuric acid solution in the bottom, maybe a half gallon of water and a healthy glug of acid. It did a decent job, but there's still a bit of rust color on the bottom. I'll try again with an undiluted solution, and I'll pick up a can of muriatic from the hardware store. I also found a thing called Evapo-rust, ordered a bottle on Amazon for eight bucks. It's got great reviews, so I'll try it on the third gas can.

 

[mesha]

Kevin, I used to work at a paint supply place and thought I heard some stuff about hydrochloric(muriatic) acid and rust. I did some digging and busted out some out chemistry notes. Here is some food for thought.

Be careful when using Muriatic acid to get rid of rust. It does eat rust rapidly, but it also dissolves the "fresh" iron. Then it activates the iron oxide Fe203 which is the reddish rust we fear. Muriatic acid(which is just another name for Hydrochloric acid) leaves a chloride molecule stuck to the Fe you are trying to protect. Essentially you are leaving a salt ion in contact with the metal. Salt water rusts faster than regular water. Your newly cleaned tank will be ready for "flash rust". You need to convert your Fe2O3 to Fe3O4 To get "black oxide" you need to use phosphoric acid. Black oxide or Fe3O4 is the same size molecule as a standard iron molecule so it will remain stable and not leave a corrosive salt on your metal.

If the rust is too thick for the phosphoric acid to dissolve quickly use muriatic acid and then dry it out and finish it with phosphoric acid. Your surface will be much less likely to get rusty again.

 

[I Lean]

And Google says phosphoric acid is available from Home Depot as a concrete floor cleaner. There ya go!

 

[Kevin B.]

Kevin, I used to work at a paint supply place and thought I heard some stuff about hydrochloric(muriatic) acid and rust. I did some digging and busted out some out chemistry notes. Here is some food for thought.

Be careful when using Muriatic acid to get rid of rust. It does eat rust rapidly, but it also dissolves the "fresh" iron. Then it activates the iron oxide Fe203 which is the reddish rust we fear. Muriatic acid(which is just another name for Hydrochloric acid) leaves a chloride molecule stuck to the Fe you are trying to protect. Essentially you are leaving a salt ion in contact with the metal. Salt water rusts faster than regular water. Your newly cleaned tank will be ready for "flash rust". You need to convert your Fe2O3 to Fe3O4 To get "black oxide" you need to use phosphoric acid. Black oxide or Fe3O4 is the same size molecule as a standard iron molecule so it will remain stable and not leave a corrosive salt on your metal.

If the rust is too thick for the phosphoric acid to dissolve quickly use muriatic acid and then dry it out and finish it with phosphoric acid. Your surface will be much less likely to get rusty again.

That's fantastic info, mesha. You're the man.

 

[JL Rockies]

This is one of those times having a resident science teacher around is winning.


Utah Bureau of Awesomeness Department.

 

[Kevin B.]

The Evaporust failed to impress. It cleaned a couple rust stains on the bottom of the cleanest can, so I went straight to the dirtiest. I let it sit several days, rotating the can once a day so that all the surfaces were covered. It didn't do much. In fairness, this can was very rusty, so maybe I just exhausted it that quick? Dunno. Back to the acid.