DO NOT USE stainless steel. I posted directions on this on another thread a while back.I found this info which I am translating, verify.
car battery charger
piece of metal preferably stainless such as tea spoon or big bolt
1. fill fuel tank with solution of caustic soda (use gloves and have garden hose in case of spilling on arms)
2. Attach minus to tank
3. Attach plus to peace of metal inserted in tank(it should not tauch tank.
If current is too high there will be a lot of bubbles. My charger has 15 and 2 Amps. If 2 Amps used it can take several hours.
Here is link, look at pictures.