What Michael says is probably the best way. PC7 will not fail if applied properly,if it help to a gas tank under a car being beaten to death through a junk yard, smashed against the ground and dragged it would certainly stay on a tank being treated with care.

I will say again though the lead is probably the best way,better than braze or weld because it involves much lower temperature.

I learned all I need to know about life by killing smart people and eating their brains.
Eat right ,Exercise ,Stay fit, Die Anyway!