Rust is not an issue on modern Fiats, they are among the most rust resistant cars you can buy.
Besides sprayed on rust proof coatings, panels galvanized on both sides account for 90% of the 500's body weight.
In particular, all the parts that make up the chassis and the most exposed to corrosive agents, are 100% galvanized.
Of these, the structures defined as safety structures, such as the suspension mountings and reinforcements for the seat belts, are made from panels with a high zinc thickness, up to 20 microns.
All the body panels for the doors, bonnet, boot lid, side panels, wings and roof are made entirely from 8 micron galvanized steel.
The exception is some of the inner parts of the passenger compartment because there is no risk at all of oxidation such as, for example, the dashboard mounting brackets.
Source: Fiat SpA
Pictures: Fiat Group Press