Sorry to see the troubles you are having with your tank.
When I got my XS2 out of storage after 35+ years my tank looked far worse than that. I could see rust everywhere in it. The bottom was a half inch thick with the remnants of old gas and rust. I spent months cleaning it. Started with putting some gas in it, letting it soak into the crap on the bottom. Then added some rocks and shook the heck out of it. When I dumped it chunks of crap the size of Snicker Bars came out. Next was water and more rocks. Shake rinse repeat several times until no more big chunkys. After that used 1/4 20 nuts in place of rocks. Shake rinse repeat a few more times. Rinsed it out real well. I had gotten the big chunkys out but the inside still had rust. Next was a White Vinegar fill and soak for a week. More rinsing. Looked better. Still some rust.I had read about phosphoric acid. Used that in it. Better, but not perfect. I wanted to use it on my bike so I rinsed it till I thought I had all the loose rust out. Dried it out on the inside, rinsed it with alcohol and then rinsed it with gas. Put it on the bike and have been using it ever since. I will admit it was not perfect. I had some rust still in it. Enough it plugged up a set of fuel filters. As time and miles have gone by the amount of rust coming out has gone down to almost nothing. As I said I spent months on and off working on it. Between times of working on it I would dry it out inside.
As you can see it's not perfect. I don't think the rust that I can see is new rust. As Jim said in order for steel to rust it needs moisture and oxygen. As Gary said gasohol does have the ability to absorb moisture. In the great state of Illinois it's hard to find real gas. My bikes get a steady diet of gasohol.
I've read all the threads about de-rusting tanks. This winter I may try to get it better. Sealer would be my last resort.
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