I've replaced old gas tanks that have looked much better than this. They may have leaked gas, but at least they still had most of their faded factory paint. This one looks to be beyond hope. Watch as Live With Creativity gives this old Honda CD70 tank a new life. I actually find it rather soothing.
Of course, it takes a great deal of work to get there. Rust was literally flaking off the tank after the bike was abandoned for many years. The gas cap was seized on, only coming off with hefty doses of lubricant and "percussive maintenance." Once the loose rust was off, the rest came out with a good deal of sandblasting. I've sandblasted rusty old wheels and found it extremely satisfying to get them down to bare metal before a fresh coat of paint.
It's hard to sandblast inside the tank, so we see a low-tech solution: pour in rust remover and a whole bunch of rocks, then shake the tank for a while. It seems to work. I have no idea if the tank had any rust holes that needed to be sealed, but now would be the time to do that. Perhaps it's already been tested and has no leaks, which would explain why it's worth restoring this tank.
A bit of body filler smooths out the pits and scratches that the rust left behind. I'm used to using this to patch holes on cars that see New England winters, but it's quite effective here. Then it's many cycles of sanding, filling, priming, lather, rinse, repeat. Finally, the tank gets a fresh coat of paint, shiny new badges, and a new filler cap.
Some people find satisfaction in doing this kind of work. Others find it tedious, boring, and mind-numbing. I tend toward the latter category, but I do enjoy watching videos like this. I actually find it somewhat relaxing to watch something I would've thrown away become as good as new once again. I also like watching someone else do the work so that I don't have to.