My next door neighbor and I tried cleaning out a gas tank. We tried gas with marbles, pee stones and gas, sulfuric acid with gravel but nothing seemed to even get close to getting it clean. I was actually posting a thread on here asking for your opinions about what we should do and the thought hit me to try electrolysis.
I called him up and told him to grab a 5 gallon bucket, battery, jumper cables and baking soda. He set it up and this is what it's doing.
The first one is when we started:
Second one is two hours later.