PVC shower chair casters rust problem

I have used PVC shower chairs since I moved to a nursing home in 1996. But that facility's shower chairs were too high, so they bought me a "lower to the ground" model, which I used for the next 12 years.

I brought it with me to this nursing home. But, I could never find the right replacement casters for it. The casters wear out because of rust, especially if they are not cleaned and coated to prevent it. When the metal parts of the casters rust, the shower chair becomes difficult to roll. If no maintenance it is done, the wheels will eventually fall off or stop rolling – making the chair unusable.

I bought myself a new shower chair, in a dark brown color. The back webbing is printed with tropical fern in "a not institutional" green and gray. The back webbing it is also braced so that it's more comfortable.

After a year that shower chair's casters began to rust. I bought a rust retardant spray at a big box store. Then a friend of mine cleaned the rusted metal parts with baking soda and water – and applied the retardant. After that the chair rolled really well for three months. Then, my friend clean the casters metal parts again with baking soda and reapplied the rust retardant.

Once that friend was no longer able to help me, the chair got no maintenance. It gets sprayed off (casters too) after my showers. But, rust is not removed from the metal parts, nor are they recoated with the rust retardant.

Two years ago the three-year-old casters were shot. The maintenance man put on the extra set I bought with it to make it usable again.

It's not quite two years later, and the chair is again hard to roll. Two or three months ago an aide ook the shower chair apart, laundered the seat back webbing, and dumped out the stagnant water in the PVC pipe. It smelled better and for a while it rolled better. But not for long.

I told the maintenance man how it had been previously cleaned and that rust retardant had been applied.. He now says there is no way he can lubricate it to make it roll better. But I wonder about that.

Perhaps, if I ask, Mike (my friend) will visit and he can clean them and apply rust retardant which has improved it in the past. If that does not work, it will definitely need four new casters.