[OzMonties]

I looked at a few used RV’s with hydraulic slides and all of them had corrosion of some form or another on the rods.
On the Rod End of hydraulic cylinders, they are fitted with a rod guide bearing, a pressure seal and on the outside which you can see, a Wiper seal. The final wiper seal is designed to remove light dirt and dust from the rod as it retracts back into the cylinder.
Most (quality) hydraulic cylinder rods have a nice thick chromium layer electro plated onto the rod during the manufacturing process. Chrome is Very hard and resists abrasion and corrosion.
The ones I saw, and some were keystone products, were manufactured as ground and polished rods only, with No chrome plating, as that saves money. So those were doomed to failure, and if you retract a rusty rod, it will destroy the seals and they Will start to leak!
So if you’re slides are extended for long periods, I’d advise retracting them on a regular basis, or at the very least, wipe the rods over with an oily rag weekly.