POR-15 VS Herculiner, anyone?
POR-15 is good stuff but... it is really $, does not tend to keep well once the can is opened, will stain your hands if you get it on your skin and makes really bad fumes. That being said I coated part of my tractor with the stuff some time ago and you can hit it with a hammer without chipping it. I've never used Herculiner but SEM Rustshield has been good to me as well.
-LY