Step 1: used combination of nuts and bolts inside the tank, with tank packed with blankets inside clothes dryer (Heat OFF) set on tumble for 30 minutes at a time, repositioning it every 1/2 hour. We have an old dryer at the shop just for that



Step 2: is a product called Metal Rescue, some type of acid but it works well and it was cheap enough



before





after



Step 3: rinsed with water and then rubbing alcohol to get rid of moisture and that's what it looks like



For good measure coated it with Caswell epoxy