Originally Posted By: turtlevette
The last rotors I got for the vette were zinc washed. It protects inside the vanes where you get a lot of rust inhibiting heat transfer.
Where I live, we sometimes have more salt on the road then snow. My Mazda 3 came in from the factory with nice zinc coated rotors, including the vanes. When it came time to change them five years later, the vanes were badly corroded.
I put in the cheapest, Chinese made rotors I could get and painted the hats only. They are about five years old now and look pretty much identical to the OEM ones that were coated. Vanes are rusted of course, just like the OEM ones were.
So to me, it makes no difference, as in my experience, every single rotor I dealt with, factory coated or not had badly rusted vanes because of the salt and heat cycles. The only reason I paint the hats is for cosmetics.