I have used POR-15 since about '88. It has held up. They have added some prep materials since then. I have used their wash and metal prep too. I buy the small cans is a six pack to keep thing fresh. If you have a large area, then buy the large can. I put a piece of Saran wrap between the lid and can to help seal it, if there is some left.
I think you need to do two or three coats of it, about 2 hours apart. Then you need to prime it about 2 hours latter when still sticky. They have come out with different formulas since I used it last.
Tom