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OT'ish Gas tank repair ideas needed

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  • OT'ish Gas tank repair ideas needed

    Hi All,

    I am in the process of restoring my fathers 37 Buick Phaeton and have a gas tank problem. First off... The tank is dry and fuel/vapor free so fire/explosion problems are not present. The problem is the tank is very rusty on the inside and there is a loose baffle ratteling around. I really don't like the clean and coat options for fuel tanks and this also does not address the loose baffle. The baffle is of secondary concern and does not HAVE to be repaired. The tank is basicly a 2 foot by 3 foot by 6 inch box tank with no custom forming except for some ribs for strength. The tank is welded togeather in the middle of the 6 inch depth, think clam shell with a flange. I am thinking of carefully cutting the weld and seperating the tank so I can clean the rust out and repair the baffle. Then having the tank zinc plated while seperated into two sections. After the plating I can solder the tank back togeather and hopefully all is well. What do you think about this idea? Any and all thoughts would be appreciated. Also, would something other than zinc be a better choice for the coating? This car will not be driven much so I think some kind of coating/plating would be best to avoid future rust problems.



    Happily working on my second million Gave up on the first

  • #2
    Read this about rust removal in a gas tank, I've recommended this for many motorcycle owners on a few forums:

    Oxalic Acid Rust Removal On Gas Tanks(Found On the internet at

    Just ordered a few pounds of it this morning, it "should" remove the rust in my Kaw tank and it's great for removing rust on shop tools or whatever too.

    Or Savogran wood bleach (Oxalic Acid), available at most hardware stores. About $10 for a dry powder to be mixed with water.

    I used this stuff while I lived in Florida where the humidity usually averaged 100% and it saved me a lot of labor ... it's Eco friendly too. Our humidity here in Alabama is just about as bad as on the gulf coast ... so even if it won't completely clean the tank rust out ... and I truly believe it will ... I can make good use of it

    Don't know why I didn't think about it sooner, mixes with tap water, flushes out easy, it won't harm paint, plastics, aluminum or anything of that nature ... just kills the rust and leaves the metal coated to help prevent future rusting.

    The guy's name is Gregg and he has a ebay store but you can buy directly from him, send payment by check or paypal. I talked to him yesterday and told him there would probably be more folks from the forum inquiring about it. He said to have whoever calls or emails to remind him they're from the forum.

    It sells for $4 a pound and he can fit 4 pounds into a flat rate priority mail package and ship it for $4.95. So 4 pounds should go along way since it can be used over and over again. $20.95 for 4 pounds shipped isn't bad at all in my opinion. The only way he's making any profit on it is by buying LARGE quantities and selling small.
    I'm probably going to set up a large vat to soak tanks and tools in.
    This stuff will eventually turn black after heavy use but it still cleans good and washes clean with tap water.
    He claims he's had several people use it for cleaning rusty tanks with great results and I know I had good luck with it before too, just never used any on a tank ... but will soon.

    Here's his info: Best to try his cell first.

    Gregg MacEllven
    Sea Shield Marine Products (sales rep)
    Mac's Pacs; teak/mahog plugs, flax, oxalic, etc.
    [email protected]
    310-547-2687 (home)
    310-547-2606 (fax)
    310-721-9667 (cell)

    Late yesterday afternoon I mixed up a batch and put it inside my original KZ tank.
    The tank had what I would call a medium overall surface rust throughout the inside and a fairly heavy rust build up along the entire bottom surface.

    The instructions suggest warm water but I talked with Gregg and he said it wouldn't really matter as long as I wasn't looking for INSTANT results and let it soak so I used unheated water from the hose and about 8 heaping tablespoons of Oxalic acid and let it soak for 24 hours.

    I just drained the tank and the water was colored kind of a light brown, I flushed the tank with clean water twice and looked inside as far as I could see with a strong miniature LED flashlight and NO RUST was present ANYWHERE including the bottom surfaces.
    The Oxalic acid left behind a off white colored protective coating on the metal surface just like Gregg said it would

    Once I got the tank dry I saturated a shop rag with gas and rubbed the white coating with it and the coating stayed put.

    But ... I will highly recommend you folks give this stuff a try because it sure takes the work out of removing rust from our gas tanks and it did not faze the paint either where I overfilled it.

    This old tank will get repainted and used now that the rust is gone ... but for you folks that have internal surface rust on tanks that still have good paint on them, don't worry ... this is the ticket right here !

    I can tell you right now that it works very well, the tanks I cleaned back in November have sat in my shop until I decided to tag & drive my 78 KZ a few days ago.

    I looked at all 3 tanks & they still looked rust free inside other than a small haze which may be simply what the metal looks like after sitting so long after being treated. I thru a 1/2 gallon of gas in it, sloshed it around, poured it out, installed the tank with clear gas line & the fuel runs out CLEAN ... no rust deposit showing up in the filter either !

    Oxalic acid WORKS better than anything I've ever tried in 30 years of wrenching. Use hot water, mix it up double or triple strength, fill the tank to the rim and let it sit overnight. If you don't get the results you want, do it again, this stuff is cheap and WILL clean the rust out of tanks without harming the paint even.

    I kept several gallons of used mix in a large plastic container & constantly throw stuff in it like a set of rusted boat trailer wheels, impact sockets etc. & it cleans them like new, may take a while but it works.

    Some tanks may require more acid to do the job but this stuff is cheap & easy to use, won't even burn the grass when poured out.

    I did a Honda tank for a buddy that had some ridiculous rust along the inside bottom flat areas & top part of the hump. I tripled the recipe & let it sit a couple of days and it came out CLEAN.

    Would rather NOT use a tank liner product that may or may not peel away ... oxolic axid won't hurt the paint either, so that's a huge plus.


    • #3
      Your second sentence is going to probably end your problem and possibly you. " The tank is dry and fuel/vapor free so fire/explosion problems are not present." I remember once a buddy and I was going to rebuild and use a old gas tank that we found. It had be laying out in the open for more than 25 years. When my buddy put the torch to it to loosen the solder and remove the fill spout,,,,,,,Wooooof! It knocked us both across the shop and bulged the tank out in the middle.. Be Very Careful my friend, those vapors stay for ever.

      I would rather have tools that I never use, than not have a tool I need.
      Oregon Coast


      • #4
        Safety should be your primary concern when doing any type of hot work on fuel containers. The best way to go about performing the repair would be to have it chemically cleaned (hot tanked). This will remove all the trash and fuel that has turned to "varnish". Then use an inert gas such as argon to purge the tank of oxygen for 10-15 minutes or however long the repair takes. Remember that fire needs 3 things to exist: fuel, oxygen, and an ignition source. By doing everything within reason to eliminate fuel and oxygen then you can just about guarantee that no fire/explosion will happen.


        • #5
          Ditto on the double extra uber care for avoiding explosions. Either fill/flood with inert gas, as noted, or totally fill with water, if that is not incompatible with the work you need to do. If you use water, it's only safe while it's full of water. You could drain the water and get explosive fumes again.

          don't fall the the trick that get's recommended here and there, "Just fill it with exhaust fumes, no oxygen no explosion." Except that exhaust from an internal combustion engine is not devoid of oxygen. It might reduce the risk of explosion, but it is absolutely not a guarantee. Don't do it.

          Good luck and keep us posted.

          Hey, how about a picture of the car. We love old iron.



          • #6
            You might want to re-think the chemical cleaning/coating route. If the tank is very rusty, the metal may have thinned significantly. I have a 1952 Pontiac Chieftain that had the same type of issue. I had it chemically dipped, and although it looked and sounded solid, it came out of the de-rust tank almost like Swiss cheese. It was ruined.

            Anyway, do what you wish. But if you have second thoughts, Eastwood has fuel tank coating products that will last for a very long time. I wish I had gone that route (and I eventually did after finally finding another tank).

            Just one man's experience. Yours may vary.


            • #7
              Like almost everyone else has said, be safe. I knew a bowling alley mechanic who killed himself cutting open a "fume free" empty 55 gallon drum that had held lane cleaner. Took 3 days to die and was a horrible way to go.

              Since you have the issue with a broken baffle you really need to open up the tank. I'd recommend chemically cleaning it before cutting it apart and I would still make sure to use an inert gas to fill it prior to the hot work. You could use dry ice for this purpose.

              I'd also shy away from the zinc plating. Read up on Metal Fume Flu with this pdf written by the American Welding Society. Not a pleasant experience.


              • #8
                At one time gas tanks were made of 'Terne Plate' which I think was a form of tin plating. I have thought that tinning the metal with solder would provide suitable corrosion resistance. It is possible to cut out and rivet or screw new overlapping sections in place. Seams can be sealed by soldering and soldering will also secure the patch in place but adding screws or rivets makes it easier. Flanging and/or use of filler material can make the repair invisible. An access panel can also be installed in the top of the tank using the same methods.

                You might want to consider adding a drain while you are working on the tank. If you do, be sure you have a large enough flange so it won't break out.
                Last edited by Don Young; 11-07-2012, 10:24 PM.
                Don Young


                • #9
                  I know this sounds like "the easy way out" but trying to repair a rusty old gas tank is an exercise in futility. Frustrating too. If you've got the tank and can make some accurate measurements, I'd suggest you look in one of those antique car restoration catalogs. You might be surprised at how many fuel tanks are pretty close to what you have.....except they're stamped out of new metal. Cost? by the time you get the original tank in some kind of condition where it might be usable, the time and energy you wasted could easily exceed the cost of a restoration duplicate tank. The other option would be to make a replacement fuel tank, or have an expert sheetmetal fabricator make one for you. Even badly rusted motorcycle tanks can be duplicated....provided the guy doing it knows how to work metal.
                  No good deed goes unpunished.


                  • #10
                    What about cutting the top out of the tank,cleaning and painting it and finding a modern plastic fuel cell from somebody like Jegs or Summit to fit inside?

                    It will still look like the original from the bottom,but be vastly better and never again any problems with rust.
                    I just need one more tool,just one!


                    • #11
                      This is the fuel tank of my 53 Hudson Hornet Coupe. Not long after I got the car I started having a problem with fuel filters blocking up, there was some sort of chemical lining in the tank that was disintegrating. I removed the tank and took it to a radiator place, who have procedures for dealing with 'live' fuel tanks. You can see from the repair scars where they cut 2 large openings so they could get an arm right in there to clean out the gunk.

                      I'm working on a 35 Hudson 8 roadster project that is missing a fuel tank, its just a box 3' x 1' x 8". I won't even bother searching for a tank for it, I'll either have a stainless tank made or I will use this as an excuse to buy a lowish end TIG welder and make my own.