Rust despite full galvanizing???

Recently I saw an Audi 100 (C4) in white, in which there were clear rust damage on the wheel cut-outs at the front and back as well as on the door edges. I knew so far only about rust-scatters à la Vectra or Omega. How can that be? The C4 is fully galvanized! How can you get it to rust? I have an 80 B4, Built 93, on which is not the smallest rust stain on the body (and that after this salty winter) is a mystery to me!