My trailer's steel bed is moderately rusty. Applying bedliner costs hundreds of bucks at Rhino. Plus a couple of hours wire brushing. So I am thinking of cheaper alternatives.
How about this:1) Make sure that the trailer is dry
2) Apply heavy oil, like 80W90 gear oil, to the floor of the bed, very liberally3) Make cutouts in two sheets of exterior 3/4" plywood to allow for wheel wells, and put them inside side by side so that they meet in the middle. Optionally glue them in that middle seam using epoxy and fiberglass tape (I did that before). Apply anti-rotting compound like Cuprinol.
That ought to cost about 30 bucks, or whatever is the cost of plywood, and should work out okay.