I am making a fuel tank for a reproduction Briggs and Stratton Motor wheel. I intend to use 2 1 lb Coleman propane bottles, with the bottoms cut off, tig welded together with a steel filler neck also tig welded in. My problem is keeping the inside of the tank from rusting and I came up with an idea - don't know how feezible it is. I am thinking of putting some Oakley 95 tinning flux in the tank after sandblasting it, and before finishing the weld then heating the welded tank to about 700F and rotating it while maintaining heat to totally flow the tinning flux over the entire surface. After cutting out the opening in the filler neck I would tin the inside ofthe filler then flush out any remaining flux - leaving the entire interior of the tank tinned and protected from rust - basically like a terne coating. 1.7 oz of tinning paste is $12.99 mini CanaBucks Can't think of a simpler lower cost source for a half gallon cylindrical duel tank - although this isn't exactly a SIMPLE one. I made a "prototype" brazing the tanks together and attempting first to braze, then to solder a red brass /copper fitting in for a filler. Not a neet job and not a liquid tight seel between the tank and filler - and a LOT of rust in the tank 3 months later.
What am I missing???? any obvious "gottchas"? ( I WILL braze "bosses" on the outside of the tank to drill and tap for the fuel fittings, and braze or tig on the mounting brackets before doing the tinning so no heating will be required after the tinning process )- then just a good cleanup and paint with gasoline-proof paint. I learned years ago NOT to use spray Tremclad on fuel tanks - - - -