To be fair I wore them 2-3 times a week running. Sweat definitely roles off my ears onto the airpods. I bet sweat is particularly corrosive. The Apple store tried to brush off the rust and it worked a little better, but not consistently.

I would recommend buying cheap exercise headphones instead of using airpods.

I also sometimes prefer having the over ear headphones for some sound cancelation. You can buy reasonable headphones plus a mic-in cable for less than $50.