@Thad55 if there is no rust slosh fuel around and dump out the debris. For rust muriatic acid slosh, let it set for a couple of minutes only, then rinse out with baking soda and water to neutralize the acid, then get it dried out and filled with fuel as quickly as possible.
I have had both a dirty tank with no rust and a rusty tank. Once each so take it for what’s its worth. After the acid and neutralization it will flash rust pretty quick so that’s why I suggest getting it dry and filling with fuel asap.
The acid is no joke. It’s an absolute must to wear a mask with filter elements (not just a paper mask), chemical resistant gloves, and safety glasses. When the acid hits the rust it off gasses a toxic cloud. I am the most absolute unsafe person and probably have 5 pounds of metal shavings stuck in my body with lungs coated in spray paint. For serious be careful with the acid and good luck!