High school :Corrosion

You may have noticed that when rusting appears on a car body, the rust appears around the break or chip in the paint but the damage may extend under the painted surface for some distance.

a) What is the evidence for damage extending well beyond the break in the paint

b) Suggest an explanation why the damage may extend far from the break in the paint.

a) Um, I'm gonna guess that the rust appears around the break so you'll see a browinsh color around the break.
b) I have no clue

I just need some simple answers, thanks in advance:)!!!