Gas Tank Cleaning Help

FirstA

FirstA

Member
I am coming along nicely on my 29 CCPU project. Time to clean the gas tank before painting but so much information on the forum. I decided to use the muriatic acid method, used 1/2 gallon to 10 gallons warm water and let work for 24 hours. After flushing is still see patchy rust spots but nothing loose. Now should I keep working on the rust that is left or just use a pencil screen and mystery oil?
 
FirstA said:
I am coming along nicely on my 29 CCPU project. Time to clean the gas tank before painting but so much information on the forum. I decided to use the muriatic acid method, used 1/2 gallon to 10 gallons warm water and let work for 24 hours. After flushing is still see patchy rust spots but nothing loose. Now should I keep working on the rust that is left or just use a pencil screen and mystery oil?
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Muriatic acid is pretty tough stuff when it comes to bare sheetmetal so make double-down sure you get it neutralized well or you won't have a gas tank any longer.

One other issue that I have never understood is that Hydrochloric Acid is often times used to help in welding Terne coated sheetmetal (I guess as a flux or something) however when Phosphoric or the Muriatic is trying to attack the rust beside where the Terne coating was, it seems ineffective. As you are aware, the tanks were originally Terne coated. My personal opinion is if you still see rust, then give it some time with an oxygenated environment such as gasoline ...and those rusty spots will be making sediment before long. As the fuel sloshes by, it creates sediment and leaves a fresh spot of metal to start rusting. Guess what happens then...!! ;)
 
Rust? Could be far worse.

Currently fighting a formerly "sealed" tank with some unknown black gas tank sealer applied maybe in the 1960's or the 1970's by former owner(s).

New ethanol gas appeared to have dissolved about 90% of it -- still peeling -- left very thick, dark brown crud/sludge/varnish which comes out with fine rust particles -- dense crud like sandy/silty mud-like substance in bottom of bowl -- repeatly filled tank with about 1-1/2 gallons of gas & drained about 10 times -- getting better -- large particles, (size of heads of pins), are for the most part, appeared to have been drained out -- still fighting.
 
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Had a 29 roadster back in about 1958, drove it home after sitting outside for ???? years with no problems. Put a battery in it, swapped 4 tires/wheels onto it from my sport coupe along with a carb and dist. Drove from stony point new York across bear mtn bridge to Bristol CT. After that had tar getting into the system. Back then was diff than today. My g/father and I took it to the int'l dealer down the street and tried steam cleaning the tank. Got some of it out. Then flipped it when I bought my 1st 32 5w coupe. Got rid of the sport coupe also. Paid $100 for the sport coupe and $75 for the roadster. Made money on both. The roadster got rodded.
Paul in CT
 
1/2 gal to 10. Sounds like a little over kill. You need to flush the gas tank out with a lot of baking soda and water. The acid will keep on eating away at the metal if you don't.

If you see brown or something dark under your sealer that's rust. If the sealer is flecking off that's the ethanol. Bite the bullet and have a radiator shop boil it out. The cost is small and well worth not having the trouble down the road.
 
The tank is not sealed and it was properly flushed out. Just wondering if I should try evapo-rust or molasses. I don't see how you could get the molasses flushed out. My only close radiator shop [50 miles] has been rebuilding my radiator for 5 months now. I would hate to give him too much to do. Might slow him down.
 
Molasses ???? ....... True story:

Knew a guy who had a syrup mill & a company truck.

He bought oil by the case for the truck & noticed a few cans of oil missing now & then, so he took a new can of oil, emptied it, put syrup in the can, ran it through his can closing machine, & placed this can with other cans of oil.

Directed a worker to change oil in his truck; but forgot about the can of syrup.

Driving home about 45 mph with worker & the engine & rear wheels locked up.

Small amounts of molasses, syrup, or sugar in gas tank or crankcase can play havoc with an engine.

Hope this helps to remember what not to do.
 
I've had a radiator shop "boil out the tank" and what a crock. Looked just like it did inside when I brought it to him. I complained and he re-did it three times. I do not believe radiator shops are equipped to clean 80 year old gas tanks and I think you would be spending money and getting something not very well done.

I took it to a metal prep place where they did it correctly, dipped it and got it back in a day looking like brand new sheet metal the day it came out of Henry's plant.
 
FirstA said:
The tank is not sealed and it was properly flushed out. Just wondering if I should try evapo-rust or molasses. I don't see how you could get the molasses flushed out. My only close radiator shop [50 miles] has been rebuilding my radiator for 5 months now. I would hate to give him too much to do. Might slow him down.
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The molassas is in a 3-1 solution with water, washes out very easily. It will clean all the rust out and not harm good metal, if done right.
 
Hi NoboD. Searching the forum gives so many different mixtures, temps, etc. that I am not sure how to do it right. What is your process? I always appreciate help.
 
FirstA said:
Hi NoboD. Searching the forum gives so many different mixtures, temps, etc. that I am not sure how to do it right. What is your process? I always appreciate help.
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Molasses works best when it's fairly warm, like 100*. If the tank is out of the car then you can set it in the hot sun for a week to let the molasses do it's cleaning/derusting. Go to the feed store and buy a large bag of dry molasses. I think I used about 1 pail of molasses to 3 pails of hot water. Mix it well and put in the rusty parts. I used a dark blue tub and set it in the hot summer sun. After a week the parts were rust free.

If the gas tank is out of the car then this molasses would be easy to use. If the tank is installed, then after mixing the molasses I'd strain it through a cloth to remove any solids before you stick it in the tank. You'll need to fill the tank to derust it all. You could then attach a magnetic engine block heater to the bottom of the tank to keep it warm and let it set for a week. Then drain and rinse and dry as quickly as possible. Then fill with good gas and 4 ounces of Marvel Mystery Oil.
 
FirstA said:
Hi NoboD. Searching the forum gives so many different mixtures, temps, etc. that I am not sure how to do it right. What is your process? I always appreciate help.
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The feed store I buy mine from sells me a liquid, very thick and stinks bad. This way there's no lumps of solid. DON'T get it on your hands and do this outside. I think it was .10 a pound last time. I too used a 3 to 1 ratio. Completely submerge or fill completely as the liquid gases and will cause rust to exposed metal. Do not seal the opening of the tank as it will blow your tank as it gases. I know someone that sealed a MC tank and went on vacation. Came home to a mess all over his ceiling and a ruined tank. I rinse throrughly and wash with Spray Nine or Simple Green, it won't flash rust. I have an A tank I did about 4 years ago sitting in my shop, has not RErusted.
 
"DON'T get it on your hands and do this outside."

You sure got that right!:eek:
I stuck my hands in the stinky mess and they didn't come clean and stop stinking for days. :mad:
Wear rubber gloves.:)
 
I have decided to clean the inside on my rusty gas tank with the dried molasses method. I purchased a 55 lb. bag of dried molasses from the farm feed store for $21. I'm trying to mix some with water in a 10 gallon pail. After an hour it still looks like grass seed in a soupy mix of molasses. Did I purchase the wrong stuff or am I supposed to strain this mix for a clear solution ?
Thanks
 
I would mix it with hot water very well, then strain it if you put it into a gas tank. It only works when warm, so keep a couple 100 watt light bulbs under it and insulate the sides, so the tank and molasses stays at least 90*.
 
Thanks Tom, I've read a lot of your comments on quite a few different topics. This site has given me so much valuable information during my restoration. much appreciated.
 
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