I just acquired a 270-gallon galvanized steel tank that was previously used as a water storage tank. I plan on elevating it for a gravity-fed gasoline tank here at the homestead. The tank has been sitting empty for several years. With all the practical knowledge out there, how would I go about cleaning out this tank of rust (and other nasties) before I fill with gasoline and begin use? The tank weighs somewhere around 300 lbs and ain't easy to move around. Also, I'll paint the exterior (probably spray paint). Do I need to prime initially?

Jack

Galvanized steel needs to be primed with zink chromate primer, or whatever you put on it will flake off. As for the inside, you have two choices, they make a gas tank sealer, that coates the inside, seals holes and traps the nasties. Wish I could recall what it's cslled! Search the web, it used to be out there, bet someone still makes it. Your second choice, as long as your positive you don't have any holes, is to just put a good filter on it to filter out the nasties. Don't forget to treeat the gas!

Many thanks Lee. Much appreciate your coaching. From aluminum airplane painting I did a few years ago, I think I still have some zinc chromate primer. I didn't know that was recommended for galvanized. Thanks.

Jack

Its awesome information filled threads like this one that makes this an every day check it out spot. Great information Lee.
Mac

I hope the info that "used to be" is still current! Things have changed so much in the last ten years, and I've kinda been out of the fray for awhile, but I know that was the way we used to do things, Jack. Good luck!

Again, Lee, much appreciate the sage advice.

Jack

Gravity tank is a environmental hazard. Put it on some 6 inch cement supports. An open cover will keep fuel in better shape. Some of newer gases have a short shelf life by the time they are delivered. Straight gas keeps better

I made a fuel tank for an old truck I had and didn't treat it. BIG mistake. filled the carb full of rust in short order. Gas will wash away any of the oils used in manufacturing so one must use a sealer inside a tank or you will pay the price. Some on a motorcycle site I used to go to tried the cheap stuff to find it would come loose and plug stuff up bad. Once it was in there it was next door to impossible to get rid of. I hope someone has a solution for this.

^^^^^
This
Don't rely on any sort of valve to stop unintended flow; eventually all valves/hoses/fittings will fail.

Check with your fuel supply delivery service. United Oil is one over here, 208 459 6363. D.E.Q. regulates tanks and can be helpful on a lot of things.

In the Coast Guard we etched with a primer we called “blue death”. It was mixed with sulfuric aid and required a respirator. Made very small batches because not much was galvanized on the boat we were painting. Just handrails.

Por15 fuel tank sealer. I have used it on several steel tanks. Never tried it on galvanized though.

Needs to be in a cool place because gas evaporates and be sure to have a ventilated tank and well ventilated area. Definitely not in a building. Use good fuel filters and needs a petcock on the bottom of the filter to drain water that is collected from condensation. Probably a good idea to have a containment of either metal, plastic or concrete. Also good to at least have empty barrels or tank you could always move it to in case of a leak, at least think of a go to plan. Needs to be an area free of brush to avoid accidental grass fire getting to it. Don't put it visible to the road or it could be assumed free gas for all.

I have a gravity flow tank I’ve used for over 40 yrs. the discharge pipe is screwed into the tank about 3 ins, so it never empties all the way. The front end is about 2 ins higher than the back so crud can settle there. I change filters once a year. Never have had a problem with this set. I also have a shut off valve if the hose or nozzle should fail.

Well, my Grandpa's old-school method for cleaning rust scale from the inside of a tank was to shovel some rocky gravel into and roll it down the hill. Then dump and shop-vac it out, rise once (with fuel or solvent that will evaporate), let it air out (sometimes with a blower) and its ready for coating. I don't remember any specific coating products.

Sure gravity tanks are a "hazard." Fuel anywhere is technically a hazard. Gravity tanks are much preferred to buried tanks around here because at least you'll know if it leaks. Containment isn't a bad idea if it suits you.

Vehicle fuel tanks have no coating on the inside that I ever saw, so why does a tank like this??

Does splash keep them from rusting maybe?

The issue is water sitting in the bottom causing rust. Water can and will condensate out of almost all fuel over time, and of course water settles underneath petroleum. Vehicle tanks cycle a lot faster (full-empty-full in a couple weeks vs. 6 months or more). Most vehicles also circulate fuel back to the tank, so any little bit of water gets stirred up and burned through pretty quickly. Metal vehicle tanks do sometimes rust out, usually from sitting for a long time.
So for a steel tank that's going to spend it's life sitting still with no circulation, slow fuel cycle, and usually no bottom drain, coating is a reasonable idea.

Used to be if you bought a lot of fuel it was cheaper to have it delivered, but now days they charge you for delivery and may have a minimum. A lot of the time the reason its cheaper by truck is because of the tax. Usually you fill out the papers with your fuel man saying its for off road use. But in cases where the price moves fast one can shop around at the best stations and with an approved 100 gal tank in the back of a pickup one can get a lot of fuel fast. The guy behind you while you are filling up may not be happy waiting. If its for off road use you can file form 4136 at the end of the year when you file your taxes and get the federal tax back. State tax in Illinois not so easy.

Jack, years ago a motorcycle shop I dealt with always went to the local small airport and got sealer from them when they had a questionable motorcycle gas tank to seal on the inside.
If you fill it with ethanol treated gas I would use the best (Startron?) gas treatment available for ethanol gas. Personally I would pay the extra for non-ethanol gas if available.
Good luck.