Gasoline tank welding

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I have an aluminum gasoline tank in the back of my truck that has a mounting tab that has cracked and needs to be welded or cut off and a new tab welded on. There is an air gap between the tank and a faceplate and another air gap between the face plate and the mounting tab. The faceplate is welded to the tank with stitch welds. See diagram - the faceplate is 1/16" diamond plate, the mounting tab is 1/8" diamond plate. This is way beyond my capabilities so my questions are: 1) Can this be welded in place since there are air gaps? and is it practical to do so? (meaning that not all the fuel could be purged from the tank. If it has to be removed there are hoses and wires and bolts etc that has to be disconnected. 2) When I call a shop, since I can't show them the picture, is there something I should mention to be sure they understand or is "welding an aluminum tab on a gasoline tank" cover it?I guess I'm hoping the 2 air gaps will allow it to be done in-place since I really don't want to remove the tank, but I'm thinking that it's just wishful thinking. Attached Images
Reply:First you need to make sure you know why it broke in the first place... and not just set it up to fail again..I would not try to weld it without taking it off and washing with soap and water....But I suppose with washing AND  an inert  purge gas in it one might do it safely...Weldandpower Lincoln 225 AC,DC with Briggs 16hp gas engine.WW2 era Miller TIG.
Reply:The reason it broke is that when it was originally welded, the tab was a little high so it doesn't lay flush with the bed of the truck and I added a thin spacer (1/32")  under the tank which made it a little worse then tighened it down with the bolt. I expected it to bend a little, but it broke instead.
Reply:You could call around but they will most likely tell you no. I wouldn't take the job for anyone unless it was removed and drained and I personally washed it out. Ive welded probably going on hundreds of gas tanks in my life and Ive only had one blow up but I was lucky. the one that blew just had enough fumes to go from a rectangular side tank to a round side tank.  But I immediately had to go to the can. If it was mine I would fill it all the way full of soapy hot water, clear to the top Then I would weld it with a spool gun, being very careful that I didn't burn threw the 16 gauge diamond plate and hit the gas tank. With it full of water the amount of gas fumes mixed with air would be minimal and all at the top of the tank so even if you burned through it would just squirt water out. You have to learn when to call em and when to hold em.  Mac
Reply:If a tank is too big to fill with water... AFTER it is washed WELL with soap and water ... I have used a good scatter sprayer on the end of a water hose... while welding...Weldandpower Lincoln 225 AC,DC with Briggs 16hp gas engine.WW2 era Miller TIG.
Reply:unless you have to weld directly to the tank it is not worth the risk. I have a customer with prosthetics from gas fumes covered up by the scent of dawn soap....  he flew a hundred yards before landing in the drink! I also know a customer who died the same way. You can weld thousands of tanks the right way and goof it up just once, thats all it takes.
Reply:I mean fill it up with water since i didnt make that clear. Whom ever welds it wont go poof then. I have seen people fill the tank up with gas but noone is going to recommend that, neither am I
Reply:Can you wrap the tank with a set of moderate brackets to it hold it down and properly spread the load around.You don't see many racers with their tanks mounted with tabs only on the bottom.
Reply:I can't run anything over the top and I can't reach the opposite side. This is a combination tank and tool box so the top is the lid of the tool box. I've posted a question under the jobs category for a recomendation for a shop/weldor in the Waco/Temple Texas area that can do this. - Maybe a different attachment method? But simple is best.