My disc brake rotors have started to corrode. What can I do? For the last two weeks, I was using my bike heavily in rainy weather. I was cycling during rain for hours. Now I noticed that the discs of my disc brakes started to corrode. What can I do now? Should I just clean them? If yes, how?
Generally, it will go away if you apply the brakes a bit (it will be a bit noisy at first, but after a few applications it will look as good as new), since the rust is likely only on the surface (this is one way to tell if a car has been not driven for a few days - rust spots appear on the brake discs, but they'll go away after a short trip around town). Otherwise, if its more serious, you can  try light sanding with sand paper / steel wool / wire brush or something similar and then cleaning the rotor with isopropanol.

It goes without saying, but, don't get oil on the brake rotors while cleaning it.