I had my new trailer sprayed with same stuff that is sprayed in pickup beds. We haul concrete and gravel. All worked well until a couple brain dead employees loaded concrete chunks with rebar sticking out and so much for protection. It’s not theirs so didn’t care. Loading chunks in the winter with dollies it’s still not slick at all. In deciding how to protect the bed I thought about plywood which I had previously used but wouldn’t last long. Then I considered UHMWPE but way too slick for hand loading concrete chunks especially in the winter. So spray on bed liner and would if it’s for a use where you have control it would be the best IMO!

Uhmw....is great for many applications

In this case I would think it would trap moisture under it speeding up the rust process

That did cross my mind

A few loads of rock will get it shiney again. No matter what you coat it with the stuff you dump will take it off. Haul some rock and keep it out of the rain.