How do I clean rust from the inside of a gas tank?

[pckeen]

I am getting an old 50s 10 hp Johnson running (just rebuilt the stator plate, and have installed all new coils and spark plug wires). I found a pressurized gas tank, but it was squirting a black oily substance out of the gas line connection on the tank. I drained the old gas, and rinsed a couple of times with new gas, but there is a sound like sand sloshing in the tank (which I assume is flaky rust and gas mixed), and when I drain the new gas, it comes out brown. The tank itself does not leak.

I've bought a new double fuel line hose, but before I install it, I want to clean the tank as best as I can. I don't want to try electrolysis.

What's the best method for cleaning an old tank like this?

 

[DeepBlue2010]

Woodonglass once explained a method of cleaning under deck gas tanks with a metal chain inserted through the fill opening and some chemicals inside the tank. The method can be tweaked and adopted to your small tank. I am sure he will stop by soon to chime in

 

[GA_Boater]

A small chain, nails, nuts, bolts, gravel, small stones - Anything hard and a couple of quarts of diesel or kerosene. Put the cap on and shake until your arms tire, drink a beer, shake some more, drink a beer and look inside to see if it looks better.

If the wife is out of town, wrap the tank in some old towels and toss it in the dryer - No heat cycle. Set the timer and drink the rest of your beer. If you use a chain, don't use the dryer. The chain could damage the pick-up during the tumble.

 

[GA_Boater]

BTW - It might help to take the 8 screws holding the top plate on to see what's really going on inside the tank.

 

[poconojoe]

Why don't you just get a new tank? It's a small portable tank. Why take a chance sucking up crud into your engine?

 

[Scott Danforth]

if it was my tank and there was rust on the inside, here is what I would do instead of the electrolysis method:

remove the top gauge assembly
fill tank with mixture of 20:1 solution of water and muratic acid.
let sit for a day
pour out contents of tank, pressure wash inside of tank (all the rust will now be gone)
neutralize the inside of tank with soda-ash and water (to prevent flash rust)
dry with air
use a liquid metal tank coating on the inside. let cure per instructions on kit (once you remove the rust, you have to keep it from coming back)
reinstall gauge assembly (with new gasket)
fill tank
go boating

 

[pckeen]

If the wife is out of town, wrap the tank in some old towels and toss it in the dryer - No heat cycle. Set the timer and drink the rest of your beer. If you use a chain, don't use the dryer. The chain could damage the pick-up during the tumble.

Are you a divorce lawyer....trying to drum up business? :lol:

Why don't you just get a new tank? It's a small portable tank. Why take a chance sucking up crud into your engine?

I have new tanks - but I don't believe they make these pressurized tanks any more. If they do, I know I can't get them locally. Ultimately, if this motor runs well, I'll convert it and add a fuel pump, but I'll still need the tank and fittings to test other old motors that I pick up.

if it was my tank and there was rust on the inside, here is what I would do instead of the electrolysis method:

remove the top gauge assembly
fill tank with mixture of 20:1 solution of water and muratic acid.
let sit for a day
pour out contents of tank, pressure wash inside of tank (all the rust will now be gone)
neutralize the inside of tank with soda-ash and water (to prevent flash rust)
dry with air
use a liquid metal tank coating on the inside. let cure per instructions on kit (once you remove the rust, you have to keep it from coming back)
reinstall gauge assembly (with new gasket)
fill tank
go boating

I like this idea - I can certainly get the Muratic acid. Do I simply fabricate a gasket, or can you buy them?

 

[eavega]

Not to contradict Scott Danforth, but for an older tank, you may want to rethink muratic acid. Muratic acid will eat away at some of the tank metal, which COULD result in pinholes developing in the metal, which is an issue if this is a pressurized tank. Electrolysis is the best method here, as it won't further strip down the existing non-oxidized metal. Since you state that you don't want to go that route, the method that worked for me on a motorcycle tank that I just cleaned out last weekend. 6000 BBs, and a gallon of CLR. Shake, shake, shake. Shake some more. Shake a little bit more (I considered the dryer method, but couldn't get the tank into the dryer). Drain, power wash with water. dry (for the motorcycle tank it was a little easier, as there is a fuel fill side and an outlet side so I could get air movement through the tank) . I agree with Scott Danforth and do an interior coating to keep the rust from coming back.

 

[GA_Boater]

No Peter, not a divorce lawyer - I've been on the other end.

Scott's way is less harmful to the marital status. It is also easier on the muscles and beer budget.

iboats carries the gasket, a Sierra replacement - http://www.iboats.com/Johnson-Evinrude-OMC-302557-replacement-parts/dm/view_id.461187

I've used gasket material like this to make gaskets when I can't find the original type. http://www.autozone.com/sealants-gl...32-in-fiber-gasket-material-sheet/106912_0_0/

 

[BWR1953]

Those old pressurized tanks are "rare" and "antique" which means expensive. I got one with my Kingfisher exactly like yours and in the same shape. Nasty, oily black gunk coming out of the tank even after rinsing it with fresh gas. Didn't want to hassle with that mess.

So I sold it as it was for $200!

 

[Woodonglass]

I cleaned both of my Old Evinrude metal tanks by removing the "Guts" then I just used Boiling Hot water and Dawn Dish Soap. Let it soak for 2 hours then drained it and then put a gallon of boiling water with dawn in, duct taped all the openings shut, and jacked up my riding lawn mower, bungee corded the tank to the rear wheel, stuck a chain in the tank and let it run for 1/2 an hour. Came out sparkling Clean. I then Had em both powder coated and they looked Brand New. Total Cost for both tanks...$50 bucks!!!

 

[Scott Danforth]

Not to contradict Scott Danforth, but for an older tank, you may want to rethink muratic acid. Muratic acid will eat away at some of the tank metal, which COULD result in pinholes developing in the metal, which is an issue if this is a pressurized tank. Electrolysis is the best method here, as it won't further strip down the existing non-oxidized metal. Since you state that you don't want to go that route, the method that worked for me on a motorcycle tank that I just cleaned out last weekend. 6000 BBs, and a gallon of CLR. Shake, shake, shake. Shake some more. Shake a little bit more (I considered the dryer method, but couldn't get the tank into the dryer). Drain, power wash with water. dry (for the motorcycle tank it was a little easier, as there is a fuel fill side and an outlet side so I could get air movement through the tank) . I agree with Scott Danforth and do an interior coating to keep the rust from coming back.

I have been restoring old truck parts and fuel tanks for 20+ years with this method. you can use vinegar as well (just as caustic as the 20:1 ratio), however I could never get the vinegar smell out of the garage or shop and I was tired of parts smelling like a pickle jar. I also have two dedicated battery chargers for the electrolysis method. if there are pin holes, they will show up no mater what. a stronger solution of acid is required to start thinning the metal (or a much much longer period of time).

CLR is lactic acid and gluconic acid and is similar in strength to 20:1 ratio water/muratic acid

I used to recommend the POR 15 products for the tank liner, however after having POR products fail lately I wont suggest it. I would look into either Eastwood, Summit Racings's, Kreem, or Caswell

 

[GA_Boater]

On linings - There are good ones and not so good ones. Some don't stand up to ethanol and some just don't really work for any gas. I can't recall the names of good coatings. I found recommendations by looking at forums for old motorcycles because bikes also suffer from rusty tank syndrome because they sit idle a lot like boats.

WOG's idea is good, except he still had to cut grass after the tank was clean. :smile:

 

[Woodonglass]

WOG's idea is good, except he still had to cut grass after the tank was clean. :smile:

Yeah, there's ALWAYS that!!!!!

 

[pckeen]

Well,the tank is sitting outside with a 20 to 1 mix of muriatic acid in it. I removed the top guague assembly, wire brushed off the black mess, wire brushed the fuel guage wire, and powerwashed as much of the gunk as I could get to from the inside.

 

[pckeen]

So in the end, I used a combination of the muriatic acid, powerwashing, and the chain and elbow grease. After about 18 hours in the 20 to 1 acid, there was still a lot of thick rust reside left - very bumpy on the inside. As a result, I used other methods, then went back to the acid wash.

I reccomend using a hairdryer blowing into the tank, on hot, after the clean - as I found that there was a little reside of water that didn't come out - and it re-rusted the tank after I cleaned it. So a quick further clean, and some restoration work, and the tank is ready to go.

Here's the 'after' pic - new hoses, new gasket, screws all cleaned up, and the sending unit and tank both repainted.

 

[GA_Boater]

Very nice, Peter.

You need a set of decals to put the icing on the cake.

 

[NAT1VE]

electrolysis, then water and play sand after the big chunks are out. The play sand and water worked great for us, and the electrolysis method was very easy. Look up how to on youtube, there are many, many videos on various methods.good luck!

 

[Woodonglass]

Uhmm what kind of Paint did you Use? Marine Gas is REALLY Hard on Paint!!!

 

[Bonus Check]

I cleaned my 1954 Evinrude pressure tank last year and repainted. it. The seal I put around the top plate did not seal off properly and the paint bubbled around the top plate. I had not put the new decals on at that point so I didn't lose the decals in the process. I have to do some more work on mine but it hasn't come to the top of the project list as of yet Some people have no idea what a pressurized tank is as they have never seen one is why they suggest you just get a new tank. I found a refurbished tank last year listed on fleabay for $450. I wonder if he ever sold it for that price. My old Fleetwin 7.5 runs well but needs the new pawl installed now.