[leddzepp]

POR works when applied directly to rust...but who wants scale and a "lumpy" finished result? Strip it down and use the metal ready prep which GRX mentioned above. It leaves a phosphorus coating, seals the surface, and gives the POR something to grab. The marine clean is by far the best degreaser I have ever used, it will put simple green, purple power, and gasoline to shame when it comes to removing caked on grease. I suspect it is bilge cleaner, as it's name suggests, and can be bought for less as such.