I know whatcha mean OT.. Before I left my old job, 1 of the last things I worked on was a JCB forklift,
The fuel tank was FULL & I MEAN FULL of rust.. & it was welded into the frame!!! it was actually PART OF the frame.. NOT just sitting in a hole, welded in, it was PART OF the frame!!!
Needless to say it was impossible to remove the tank & replace it , that's how bad it was..
or do a GOOD job of cleaning it..
It did have a plug on the bottom but the thread plug in the tank went up about an inch, so most of the rust flakes stayed IN the tank..
HEY, NO PROBLEM, I'll just go thru the top?? NOPE.. I pulled the "access plate" it was just big enough to get your fist in..& what was there?? A BAFFLE PLATE.. running across the top.. you couldn't even SEE inside the tank..
We ended-up calling a "fuel polishing company".. they have spray nozzles on the end of their wands & then suck or drain the fuel out & run it the several different micron filters & the same fuel goes back in..
I told the "foreskin" that it was done & send it back w/ NO WARRANTY cuz there was NOTHING ELSE we could do..
THAT was something I'll never forget.. a RENTAL fork lift w/ a fuel tank as part of the frame.. Brilliant !!!!