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  1. #1
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    Default Best way to fill pinholes

    I've got some pinholes on some 45 tanks I just cleaned out and have heard a couple different ways to fill the holes. Tig, braze ,silver solder, lead.... Are there any downsides/ upsides that I should consider on any one of these methods

    I have an oxy acetylene rig, but am not averse to paying someone to do it by another method. Also no I am not interested in coating them

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    I have never done it, but the Indian tank restorer guys use brass screen and solder/silversolder, just a fyi

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    Brazing, although an antiquated process of repair, is useful if your planning on maintaining the period correct look of the tanks, as thatís the methodology that would have been classically used. My 45 bros almost exclusively use the technique with repairing old tins that will remain otherwise untouched. It can take some time to perfect the technique, much like properly sweating a copper pipe but itís pretty straightforward.

    If your planning on painting anyhow and your going for strength and efficiency farm the work out to a good TIG welder. The temperature control in terms of not fucking your tins is there and a good hand will make light work of your issue.
    Last edited by ExplodingCoffinEmporium; 08-12-2022 at 6:12 PM.

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    I would say first off is you are dealing with fuel tanks.
    That being said, I was taught that no matter how long ago, how many times rinsed with water, and whatever, you need to displace any oxygen that can become present lest at least having an explosion.

    I have a 2" natural gas rubber hose that I clamped to the tank at the filler cap hole. The other end slipped over the exhaust pipe of a running vehicle. The carbon monoxide displaces the oxygen this way, just give it a couple minutes being sure it is still connected good.

    This worked for me without a problem. Best to be safe than sorry.

    Story: a friend wanted me to braze on a car tank removed once. I insisted no, he persisted in telling me look, rinsed with water numerous times, in fact it had about a quarter tank of water in it when he talked me into it.

    I was leery, as I got started with my oxy-acetyline torch, the gases inside that tank ignited, popped, made the tank jump off the ground about 6 inches (with me on top of it). It even swelled the tank a little.

    Needless to say, I was nervous, cut the torches off, and told him to take it somewhere else, not me.

    Be smart, work safely. It's the gas fumes and not the gasoline itself that ignites.

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    I have fixed a lot of things with silver solder. I'd absolutely use it on a pinhole in a tank.

    Be careful heating gas tanks, though.. Even if they're old.

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    A discovered pin hole, AKA, rust, means lotsa things: In other words, you have lots more just waiting to breech the surface. Patching one, and then painting the tank, will just buy you a little time before you need to patch it again, meaning more labor, down time, and paint

    To me, patching a tank doesnt make sense on gas tanks that are available aftermarket. Patching only makes sense on rare tanks: Just me

    By coating, if you mean you dont want to coat the inside eventually, is just asking for more pinholes.

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    Looks like silver solder it is. I paid a pretty good amount for these shit tanks off eBay, and I've been pretty stubborn on rebuilding and fixing everything and only using OEM parts minus the nuts and bolts so the tanks will stay. The more I put into it the more it feels like I've earned it , or something like that, so if I gotta fill some more pinholes later on, that's ok. They've got cool old paint so if like to keep them the way they are for the most part.

    I never thought about the exploding gas tanks. I'm having a hard time cleaning the oil tank with all it's sludge. But I did the gas tank and it came out decent, but I didn't know what would keep it from flash rusting so I dumped some oil in there.how should I clean that out before welding and keep it from flash rusting?

  8. #8
    Liam123
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    I restored a gas tank on an Indian dirt bike that was in horrendous shape (had a pinhole, sludge, and a few dents). It might not be period correct, but I used the rust remover you can get at orielys to clean it out (works great! kills sludge too), afterwards I rinsed it with water and then acetone to evaporate the water. Then I plugged the hole with a gas tank repair putty from jb-weld, then red-kote'd the hole thing.

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    I never thought about the exploding gas tanks.
    This is an entirely different topic I am not personally familiar with. (<- Emphasis added) But, years ago an ICAR certified structural welding and sectioning course I took discussed welding on gas tanks. The instructions were not to.

    But.. if you had to do this, we were told to wash the tank out with water, fill it with water, than drain the water out with a lit torch in the neck to slowly burn off gas fumes..

    Again.. I haven't tried this. (<- Emphasis) That is what they said.

    I happen to have an exploded harley tank out in the back building that some guy put a stud gun on once, to pull a dent out. It scares me, so I would probably look into a chemical method first.. Then I might back it up with the torch method.

    I have used CLR very successfully in this regard. Others have used Muratic Acid. I would be very careful heating any tank as the chance for injury seems high if you are careless.

    As far as treatments and rusting, I know Doug told me once that he used a product called "Ospho" in his gas tank and I got some and am impressed with it. In fact, I am going to put some on a rusty tractor wheel today before I paint and put a tire back on it. Perhaps he will chime in and fill you in on the details?

    IF you have a borescope, it would be nice to get a look in there to see just how bad it is and what the chance of a successful repair would be without having to revisit this again?

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    crush up about 1/2 to 1 pound of dry-ice. stuff the tank full. We use it for welding on industrial gasoline transmission pipelines
    Forgot to mention, leave the cap off and all fitting open otherwise the tank will expand.
    Last edited by Smiley; 08-18-2022 at 10:44 AM. Reason: added info

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    Quote Originally Posted by Smiley View Post
    crush up about 1/2 to 1 pound of dry-ice. stuff the tank full. We use it for welding on industrial gasoline transmission pipelines
    Forgot to mention, leave the cap off and all fitting open otherwise the tank will expand.
    This is an interesting approach that has never occurred to me. Not only would it keep surrounding metal cooler, it would starve the oxygen from the tank. Great idea!

    In the past I have always rinsed the tank half dozen times with water, and then right before welding put a torch to the bung... You will always get a light 'fooohm' from it, but it never has been violent. However, I think I'll try using the dry ice next time.

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    The trouble with pin holes is that the area around the hole is usually really thin and corroded. I prefer to cut a patch going back to good metal. Your going to have to sand/grind your welds for paint anyway, might as well give yourself a good base.

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