I have used POR15 quite a bit, the issue with it is when the metal doesn't have rust on it. POR15 is a magnet to rust, to good steel, not so much. If you are applying it to steel that is not rusted you need to clean it extremely well (POR15 sells a cleaner too) and then apply a metal etching product that POR15 sells and leave it on for a while to etch the metal so that the POR15 will stick to it correctly. I have yet to have issues following POR15 instructions, but I have never applied it to really clean new metal, where most of the failures happen. Also, you never want to put POR15 where it gets direct sunlight, the product is not UV resistant and will degrade rapidly if it is in direct sunlight. I can tell you one thing, when POR15 stick correctly to metal, it is an extremely tough and durable surface. I have had floor pans that were POR15 coated and after the coating water got in the car and sat for weeks, and it is as if the metal is now impervious to rust and water, the water just sits on top of the POR15 and will just evaporate without rusting the metal underneath, or you being able to see any rusting coming up from the area. If that stuff falls on your cement floors, it is there forever...