DerbyDad03 wrote:
....
All other things being equal (weather, moisture, etc) as they would be,
does the mere presence of rust on one surface make the other surface
more apt to rust?

No. If anything, the rusty surface will tend to inhibit or slow down
additional oxidation of the material as it tends to act as a barrier.
Cleaning the rust layer off exposes fresh material to be oxidized.

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