Cleaning a fuel tank

For what it's worth. I've used a 50/50 mix of vinegar and water on motorcycle tanks that were rusted like that. After power washing the inside best I could. I would fill the tank. I added a bunch of old nuts and bolts. Let it sit for 4 or 5 days shaking it every time I got a chance. They have always cleaned up really nice. I used a tank coat after. A little tougher on a truck tank.lol