Like some others here, I think dirt and grime are more an enemy than water. My tractor gets rinsed with every rainfall. I also pressure wash frequently, even around greased pivots...but don't be shy about pumping a squirt or two of grease in fittings at joints that have been washed. Also, for those pesky little rust spots, keep a wire brush and a can of flat black or orange paint handy to touch-up those areas. Touch-up the easy stuff every so often. Once a year, every spring, I have a "paint day" where I prep, prime and paint spots that have been overlooked throughout the year. Even though the fresh paint stands out against the old paint, it still looks and is better than rust. /forums/images/graemlins/grin.gif
OkieG