More asme tank questions

It's nuts and bolts and a hose/tubing connection. Or maybe welded. If you can't identify how it is mounted, in person, looking at it, then you're probably not getting it removed under your own power, even with advice from the interwebs.

Rust = Oxidation
Oxidation cannot occur without oxygen. If you submerge bare steel completely in water, it will not rust (theoretically). There is still some oxygen in most water. (And I don't mean the O part of H2O, has to be O2)
Rust "under" the paint means it got oxygen to it. Either from the inside or the outside. From the inside would mean it's already rusted through. From the outside = damage to the coating, or a coating (paint) that was not completely impervious.

The paint can look pristine but somewhere there is a pin-hole bad spot. and that's all it takes.

Unless the rust is Serious... Just wire brush (Brass or nylon please) and repaint.

If memory serves an ASME tank must have a minimum of 0.303” wall thickness and be made of high tensile steel for impact resistance. That’s almost 5/16” thick quality steel.

Paint or no paint, the vehicle would be in the scrap yard long before the tank was rotted through.

I'did see it bolted to an iron plate, I think. Maybe some weld too, I will look at it tomorrow morning again. Maybe it is rusted from inside out. I'm going to get a mobile tech out and get advice and probably have him remove it. Because of my acid reflux I cannot work under the vehicle. I want to have that rear mud flat removed because it prevents air from flowing from the back to help keep the underside dry. ( while under my rv carport) It appears to be bolted and that Doug

Man, you're threads are akin to trudging through knee deep mud with a 50lb pack on yer back....
First, you have 3 or 4 threads for the same issue, one being about how you like to eat raw food....or something.
Second, you continue to ask the same question repeatedly, but slightly different. And the only clue you've provided is the propane filler dude said it's rusty.
Third, you've never even mentioned if it actually is still holding propane....
If the rust you see was from the inside-out, you would not have been at the propane filler place because there would be a hole in the tank.

Fourth, you're now talking about "blasting" the whole undercarriage?

I feel bad that all of this is so confusing to you, on even the most basic, conceptual level, so trying to help here.

DO NOT take a sandblaster to ANY part of your motorhome.
If it is actually corroded bad enough that you think things are rusting through, you will turn your presumably serviceable camper into
something that will only be suitable for the garbage dump/recycler.
If it's not corroded bad enough to be rusting through, then you're wasting your money. BTW, blasting will only get portions of the areas.
But given that you don't actually know how rusted it is and can't get under it and wouldn't be able to accurately assess anyway, your best bet it drive the ____ out of it until something critical breaks or falls off and then pursue the landfill/salvage option.

Lastly, a couple pics would help the folks who have been giving you suggestions for over a month now a little context to be able to make at least somewhat educated suggestions, based on visual evidence and not random posts about your propane tank.
Good luck!

I think we've hit our limit on threads about this rusty tank.

I forget (because there have been so many threads on this same tank), but at some point did we rule out just replacing the tank?

I suppose that's just a rhetorical question since I'm closing the thread. Regardless, I think this topic has run its course.