Remove caked on salt stains?
 

My vinyl pool cover was obviously not taken care of by the PO. It's a salt water pool and there was a small tear in the cover that allowed some of the water to get on the cover.

It sounds like warm water and vinegar is the solution so I tried it and the newer salt stains just about washed away, but the thick, caked on stuff just sits there.

I've tried stiffer and stiffer brushes in addition to water/vinegar, all purpose cleaner and a plastic razor blade. Small pieces chunk off here and there but overall nothing seems to work

Any advice on very old, caked on salt?

Could you put something like a board under the corner and tap with a hammer to remove the majority of the think salt?
Then continue to clean with a tile and vinyl cleaner.

I was able to do that to a certain extent, the downside is the residue left is just as stubborn.

If nothing can be done that's fine, it's still works, just looks a bit unsightly. I have fixed the rip that was allowing the salt water to pool and dry up so it shouldn't happen anymore.

Might try some LimeAway on it. Sounds like it could be more than just salt deposits.

I would try a vinyl linear cleaner, it has a certain amoung of acid in it, which should help break it down.

You sure its salt and not hard water deposits(calcium)?

And scrub with a hard bristled brush. An acid brush would probably work well.

Ya it's salt and possibly calcium mixed in. It's a salt water generator system so both are present. The small tear allowed the salt water to leak through to the top and pool, then it would evaporate...rinse and repeat for what looks like a couple years. I'll try the liner cleaner