Gas tank cleaning…?
 

I was wondering how one goes about cleaning a gas tank off of an IH Cub Cadet. There is some rust as well as some red tarnish in the bottom. I want to have this thing very clean not only for the engine’s benefit, but also to make sure it safe for me to do the welding I have to do to the bracket.

Try lacquer thinner first. Another fluid to try is acetone. Be careful with both. Wear latex gloves and do not breathe the vapors.

Then wash it out with hot water and yer favorite dish soap, taking care to use HOT water.
then flash the tank with your lit propane torch,( sticking it in the filler hole after tank dries) the worse it will do if properly cleaned out is nothing, or a slight whoosh maybe if a little residue is left in a tank seam.
I've been welding gas tanks for 60+ years, never had one "done blow up" as they say in NASCAR:beerchug:
FWIW some of the newer tanks like on Briggs have an epoxy sealer or resin in the seam of the tank halves.
Welding heat will make those seams leak.
Also older kohler tanks that have seems soldered or outlet bungs soldered, they can leak requiring re sweating the seam or bung when heated enough from welding.
Don't singe yer eyebrows or beard/mustache while flashing :biggrin2:

fill and soak for a couple days with vinager. 15 marbles slosh around to loosen things up. drain. wash with hot dawn soap & drain. do your soldering quickly. get some MMO in there or premix cause of flash rust from vinager.

clarification of jcubtroy’s response
 

So fill with vinegar and let soak a couple days. THEN put in 15 marbles and slosh around. And then drain vinegar and marbles. Wash with hot water and dawn dish soap. Why should the water not be too HOT as ol’George mentioned? Weld/solder in timely manner. What is MMO and what does it do? I use apple cider vinegar, NOT plain, correct? thanks for your time

MMO, Marvel Mystery Oil

MMO usage
 

How do I use the MMO in this case? How full to I need to fill the tank with it? How much of it will I need? etc… I’ve never heard of MMO before but it is sounding like a good product from what I hear online.

I would use "hex nuts" ie: 1/4-20. The hex edges, when shaken around, will loosen the scale up.

Let the vinegar soak for 48 hours, then use the hex nuts.

I've used stone about the size of your small fingernail (#8). Small handful shake well. Then wash. I have local automotive gas tank repair shop do another. He did a good job unsoldered then resoldered tank.

lawn boy, sorry i take some things for granted. with the white vinager after a couple of days , i,ll scrub the outside the vin. & baking soda. kinda watch putting alot of baking soda in a tank with the vin. you,ll find out. you can rinse the tank then after soldering with kerosine. the oil is too coat the tank.

FYI, there is a baffle in the tank so the marbles/nuts/stones will not clean that area.

Thanks for the advice everyone. The only thing I’m not understanding is how to use MMO after I weld and how much will I have to use?

Are you welding the broken bracket that holds the tank on? No need for mmo, remove it and repair.

Response to Darkminion
 

I also need to clean the gas tank DarkMinion.

Lawn boy, If you do the vinegar way or weld, put some kinda oil in tank to coat it. Not a lot, just sloosh it around and drain. I use MMO for numerous tasks, so I always have some.

Clarification
 

So I fill with vinegar, let sit a couple days.
Add hex nuts, slosh around.
Drain, wash with Dawn and warm water.
After rinsing, slosh around MMO in it.
Do my welding last because I have to drive up north to do the welding with a relative. I am still learning how to weld and I found out that my neighbor’s welder no longer works.
?

There's this stuff called Evap-O-Rust that's about $25-$30 for a gallon at tractor supply. It's really good stuff and works better and faster than vinegar, and won't accidentally discolor metal red from sitting too long (It'll darken metal though if it sits for over 24 hours). I just used it to do my tank. It's reusable for several uses so don't just dump it away when you're done. Run it through some cheesecloth to catch the chunks of rust and then re-bottle it.

EvapOrust
 

I’ll pick some up.

sounds like your puttting a system to get the job done!!!!!

That’s what it’s turning into I guess, Lol.

I have also used this with great success. I have been using the same gallon container of Evap-O-Rust for over 10 years now. If there's flaky rust in the tank I let it sit for a day or so, turning it every few hours to make sure all surfaces get soaked. If it's not bad it may only take an hour or so. Make sure to fill it back with gas fairly quickly because once it's cleaned to bare metal it will flash rust pretty quickly if you let it sit empty.

MMO purchasing
 

Where can I buy the MMO?

Anywhere. Big Box stores, Auto Parts store, Farm/Ag Stores, Hardware stores, even Wal-Mart.

Response to R Bedell
 

Oh, okay. I’ve never noticed it before in stores. Thanks for letting me know. I’ll look next time I’m in town.

32oz bottle at Wally World - $7.48 (1 gallon $21.97). Both are in stock at my local store.

Just checking
 

I’m just making sure because I’ve never done this before.
Evapo-Rust will not cause flash rust, correct? I know vinegar would.
The DAWN and warm water will not cause flash rust so long as I get the MMO in there after rinsing thoroughly, correct?

Flash rusting is not caused by vinegar nor Evapo-Rust.
It is caused by humidity (moisture) in the air attacking the newly cleansed ferrous metal of the tank.

MMO to prevent flashing was a suggestion, not a requirement.
Any thin, mild lubricant that you can fully coat the inside of the tank with will suffice,
Something such as transmission fluid or light oil reduced with kerosene.
Then just rinse the tank out with gasolene before using.