I don't think I would call it corroding but all of the organic based plastics can and do lose "plasticizers" over time. It is the reason that the plastic covering the dash in your car ends up cracking if you don't put a surface treatment on it when you wash the car. We have all seen old air line tubing that has gotten stiff after a year or two. The same thing will happen to your seals and when they are a bit stiff they don't seal well.
