unbelievably I had a pinhole apear on a newly painted (and welded other holes) tank, welding would have spoiled the new paint, so I cleaned it with de-oxc, which is citric acid based,plugged the hole with chemibval metal (on the outside) left the tank full of deoxc for three weeks, that found another pin hole,which started to drain the fluid, plugged that with chemical metal,left it to soak for another three weeks, then I sealed it with "Slosh" (on e bay) and left it another three weeks, there were stalagtites showing under other (not plugged) pin holes witch I trimmed with a junior hacksaw, and all is well.
As a test I allowed the residue of the Slosh to cure in the supplied tin, on one side, then I punched a pin hole in the lid for a vent, half filled it with fuel, and have been draining the tin, and refilling every couple of months, no sign of deteriouration of the Slosh so far, and the tank is fine, which of course you cant see into.
CLEM