The 78 and 79 Alfettas didn't rust worth complaining about, at least here in the NW. We owned both a 75 sedan and a 78. The 75 rusted before our eyes, but the 78 had 180k miles on it when we sold it, and it basically had no rust problems at all. We were very pleased about that.
Story I heard in England was that Fiat got some crummy steel from USSR in exchange for building a Lada plant there. Fiat used that steel in their mid 70's cars of all stripes, including Fiats, Alfas, Lancias, Ferraris, etc. That steel rusted no matter what the protection. Friend in England saw Lancias being recalled and destroyed because of the terminal rust. They changed the steel to something better in 78 on, thus no problems worth talking about with those years cars.
89 Milano (wife's daily driver since 1989, Shankle Sport)
91 164S (my daily driver since 1994)
94 164LS (~Q) (trip Alfa since 2000)
72 Morgan 27 (water time since 1976)
previously owned since 1964:
62 Morris MiniMinor 850, 67 Austin 1275 Cooper S (Downton 3/4 race), 64 Giulia Sprint GT (1st red one made), 72 Fiat 128 Sedan, 75 Alfetta Sedan, 78 Alfetta Sedan, 78 GTV, 81 GTV6, 86 GTV6