Wouldn't the paint just wear off as soon as you used the brakes?

 

He didnt mean to powdercoat the rotor surface used by the pads, just the centers that mount to the rims. attempting even to powdercoat the braking surface=fail.

 

yeh, brakeing surface=no way in hell. i would hope he wasn't that dumb.

if you are talking about just the inside, then

I don't want to say it for sure,, but i dont think 400f would do anything to the metal rotors, its too low.

DOT3 brake fluid boils at around 400f, DOT4 boils at 445f, bikes use 4 so it is less likely to boil under heavy brake use (not a hard stop, but repeated use at say a track.) race bikes use even higher grade fluid, for the brakes to get hot enough to boil the fluid they have to get that hot or hotter.

you may want to consult an expert on this, but how I look at it, if normal (though heavy) operating temps are in that range, baking them should hurt them.

plus 400f is not even close to "hot" when it comes to working with metal.