I previously asked this question:
People are saying one needs to sand down to bare metal then paint over to prevent rust from spreading.
However it seems to me that the day I had the collision that rust appeared instantaneously. This would mean it was already there under the paint work and didnt appear over time.
If so why cant we just paint it(as it would have been before the collision), why do we have to sand it down to bare metal.
I could be wrong but I recall that appeared as a result of piercing of paint and so that might be the original metal?