First info: let's assume a painted aluminum surface that is scratched in a small spot with a non-humid climate, if it were steel we would see rust over time, but being aluminum will it protect itself even if the rest of the surface is painted?
Second info: let's assume a motorcycle aluminum alloy frame, will the imperfections / impurities of the metal itself inevitably create corrosion? The only way to stop corrosion in these areas is to isolate them from oxygen or, once the imperfection is exhausted, will they go to passivate themselves again, stopping the process?
Third info: what is the best way to degrease bare aluminum in addition to neutral soap? Isopropyl alcohol? White spirit?