NAPA’s Ultra Premium brake rotors are 100 percent polymer coated, which makes them corrosion resistant. Rotor edges and vanes stay cleaner longer, optimizing air flow and product performance. It also helps prevent rust from forming along the outer edges of the pad swept area.
From a NAPA Store In New York: The three rotors in the photo were submerged in 10 feet of water for several days during Tropical Storm Lee when the Susquehanna River overflowed its banks. When the water receded, the uncoated rotors were covered in a layer of rust. The coated rotors were not affected.