2000 Subaru Legacy Anyone else having windshield wiper arm

Strangest thing, I live in the rust belt but not near the ocean. The wiper arms are heavily pitted between where they bolt to the car and the thin arm that holds the blade. The arm that holds the blade looks great where the half that bolts to the car looks horrible. I was able to fix it by removing the wiper arm, grinding the aluminum more or less smooth, then priming and painting. Was there a recall, hard to believe aluminum would corrode so much, I've never seen anything like it.