I cleaned up my snow blower this spring with Por15. I was amazed at the stuff. It goes on very smooth and glossy and freeking hard. I have yet to really put it to test in the real world, but I imagine it will be twice as durable as the factory finish that was used in the areas I put it on. I spilled some on my garage floor. I imagine it will be there when I leave this world. I have made a half hearted effort to chip it up, but it is really stuck and durable.
I would love to use the stuff for a lot of things, but for two reasons I do not. First, it is expensive and second, it takes like a three step process. I just wish you could spray it on and be done. And not have it cost so much. Oh, and if it is exposed to direct sunlight, you need to top coat it with something as UV light breaks it down.
If I ever buy a new riding mower, I will probably take the deck off and coat the entire bottom side with Por15 before I ever use it. No worries about the deck rusting out.