I am installing new OEM front brake rotors. The entire rotor is coated silver including the friction surface. I don't recall that on the new rear rotors that I did last year; but, my memory isn't perfect. Is that a zinc coating and does it need to be removed from the friction surface? I wiped the friction surface with both Acetone and Laquer thinner and it didn't dissolve; so, my thought is that it is not meant to be removed; but I do not recall encountering a new rotor without a machined surface. Except for the rears, my last replacement of rotors was years ago on another vehicle. I was expecting cosmoline or some environmentally coating on the friction surface that needed to be washed off. Does this stuff just get removed while bedding the brakes or does it need to be removed with a scuffing disc. No mention in the workshop manual that I've found.