Any way to prevent evaporator rusting

[fat bob]

I've got your standard evaporator with copper tubes, aluminum fins, and galvanized frame. It's starting to rust, especially the screws in the frame which are galvanized. Would stainless screws help or make it worse? I suspect with three different metals in a wet environment rust is inevitable, but would appreciate any magic solutions.

[tpa-fl]

Usually the mechanical parts of the system fail long before the structural integrity of the unit fails.