Originally Posted by
3alarmer
.
...it happens regularly enough with alloy parts in steel frames that it's a concern for me here. And I live in the Central Valley of California, so pretty dry.
Consider yourself fortunate, and continue to
use grease or anti-seize when you reinstall these things, for the sake of the children. 
+1
Always apply a thin coat of waterproof grease to the seatpost and stem when installing them.