YES! The tractor in my profile picture, a Ford 3000 diesel, is a very good example. It wasn't fertilizer that rusted it, but alum, which is almost as corrosive as salt IMO. I have a spreader identical to the one in the picture posted by bdhsfz6. I owned a broiler growout farm for 30 years. I spread 4800 pounds of granulated alum every 6 weeks, between flocks, 6-7 times a year to control ammonia in the litter. The alum was granulated, but had fines in it that made it very dusty. The back of the tractor was coated in this dust, and some of the granules when I got done, every time I used it. When done spreading, I always, and I mean ALWAYS washed the tractor and spreader thoroughly without fail. I didn't have a pressure washer at first, so I just used a garden hose and good nozzle. I got a pressure washer a couple years later, but it was only a cold water washer. The alum dissolved easily, and I thought I was doing an excellent job washing it. But, as HayFarmer mentioned, after a while I decided the water was just washing the stuff into the cracks and crevices around the back end of the tractor. I have pictures somewhere of the inside of the rear wheels, which is where most of the stuff landed, and where they were completely rusted. In April 2022 began a restoration job on that tractor, and the first thing I did was take pictures of everything before I started disassembling it. The rear wheels were the first thing I worked on. As it turned out, while the rust looked awful, and the paint on them and the whole back end of the tractor was gone, it wasn't really that bad underneath. None of the steel was damaged, but the paint was gone almost everywhere, replaced with rust. It extended forward to under the seat, on the brake and clutch pedals and linkage, footboards, etc. I disassembled everything, sandblasted what would fit in my Harbor Freight sandblasting cabinet, cleaned up the rest with wire wheel on a drill and angle grinder, and used rust converter where I couldn't get with sandblasting or tools. I primed everything before painting Ford blue, or Ford gray on the wheels, and as of right now, I'm about 80% done with the restoration. Everything is done from the seat forward. I've still got to prime and paint the back end, rear axles, and transmission. It's running and hopefully will be done this summer. From what I've seen of the pull-type fertilizer spreaders at the local farm supply plants around here, there's not much you can do to rust-proof them. I sold my farm and retired 4 years ago, so it's no longer an issue for me.
