Cleaning the Gas Tank
- Thread starter Ken/Alabama
- Start date
I might not get a lot Amens on this approach, but here's my process. My tank had a thin rusty coating on the inside and occasionally, some would break loose and find its way into an inline filter I had added close to the tank and clog up the fuel line. I removed the tank and poured in about 2 gallons of phosphoric acid and sloshed it around frequently to make sure all the inner surfaces were getting wet. After about a day of sloshing, I poured it all out and let it completely dry inside. The phosphoric acid dissolves the lighter film or rust and chemically converts the remaining film into a rock hard substance that is neutralized. I didn't use any coating inside and have not had any ill effects of rust particles or contamination in my fuel line and the inside of my carb bowl is clean and rust free. To help maintain this condition, I use Marvel Mystery Oil at every fill up to help keep a light oil coating inside the tank. I did this 4 years ago and so far, so good.
Roger/Sacramento
Senior Member
My '41 pickup tank was nasty. I put sharp edged rocks and a couple of gallons of gas in the tank. Shook it back and forth multiple times over two days and poured this out. Repeated until it looked clean. Then used a tank cleaner solution. Then used POR 15 sealer. Been good for 10 years. I use non-alcohol gas.
V8COOPMAN
Well-known member
That's called 'Killing two pigeons with one rock'. The best part is the phenomenal length of time you get to COMPLETELY slosh that tank around a full 360º, in three planes no less, while not even breaking a sweat like you would just standing there and shaking that tank by hand.
Coop
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Kube
Super Moderator
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Strap your tank to your tractor wheel. Put a couple of short lengths of heavy chain in the tank with a couple of gallons of kerosene. Go plow the north forty for an hour or two. Tank should be really clean inside by now.
Coop
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Ya tell me this now? After I sloshed that big ol' 31 Buick tank around by hand last summer? Now?
Ken/Alabama
Well-known member
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Strap your tank to your tractor wheel. Put a couple of short lengths of heavy chain in the tank with a couple of gallons of kerosene. Go plow the north forty for an hour or two. Tank should be really clean inside by now.
Coop
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Well darn, I guess I need to go buy me a tractor so I’ll be prepared for next time.
Model51
Well-known member
McGarrett's use of phosphoric acid is what i have done. A dilute phosphoric acid solution (10-20%) works gently on mildly rusty steel. Phosphoric acid converts iron oxide (rust) into iron phosphate. Iron phosphate does not rust, but the thickness of the iron phosphate coating only works for mild exposure to water and oxygen so it's not a bullet proof coating, especially with the accumulated water inside a gas tank from ethanol's water attraction in modern gas. Phosphoric acid is the primary active ingredient in most rust removers. The commercial solutions also contain a few more chemicals which help promote the reaction and provide additional anti-rust coatings.
Phosphoric acid concentrations greater than 20% risk removing the base metal if left too long in the tank. It works too fast for my liking and must be watched carefully which really isn't possible inside a gas tank. Once the rust is no longer visible, any more immersion in the acid solution is just eating away the good steel. The conversion is also temperature sensitive. It works best at a temperature over 90F and won't work at all below 50F. Look at the old Ford Rouge assembly line movies showing dip tanks where they first dipped whole fenders in hot phosphoric acid and then hot rise. Both tanks are near boiling temperature. The phosphoric tank is hot to work fast and the hot rise is to promote fast drip and flash drying of the now hot metal parts.
I made a 2x4 frame to fit the perimeter of my gas tank then sandwiched this with two round 3/4" diameter "wheels". I rolled this contraption up and down the driveway with 2-3 gallons of solution on a hot summer day (95F) and the result was a very clean tank interior - at least the parts I could see with a 16" borescope. Who needs a gym, since I don't have a tractor, this is the next best thing. I also let the tank sit in the sun for a while in several positions to make sure the chemical reaction had plenty of time to work and get into every seam and crevis. I rinsed the tank with hot water three times to flush the residual acid and any debris from the tank to stop the process.
Phosphoric acid concentrations greater than 20% risk removing the base metal if left too long in the tank. It works too fast for my liking and must be watched carefully which really isn't possible inside a gas tank. Once the rust is no longer visible, any more immersion in the acid solution is just eating away the good steel. The conversion is also temperature sensitive. It works best at a temperature over 90F and won't work at all below 50F. Look at the old Ford Rouge assembly line movies showing dip tanks where they first dipped whole fenders in hot phosphoric acid and then hot rise. Both tanks are near boiling temperature. The phosphoric tank is hot to work fast and the hot rise is to promote fast drip and flash drying of the now hot metal parts.
I made a 2x4 frame to fit the perimeter of my gas tank then sandwiched this with two round 3/4" diameter "wheels". I rolled this contraption up and down the driveway with 2-3 gallons of solution on a hot summer day (95F) and the result was a very clean tank interior - at least the parts I could see with a 16" borescope. Who needs a gym, since I don't have a tractor, this is the next best thing. I also let the tank sit in the sun for a while in several positions to make sure the chemical reaction had plenty of time to work and get into every seam and crevis. I rinsed the tank with hot water three times to flush the residual acid and any debris from the tank to stop the process.