[Live by SI]

This is a problem area for our cars, something that is just starting to come to light now that they are getting to be 3-4 years old.

I would highly suggest that anyone living in the salt belt or state/ province that receives snow or even if you keep your car outside, have a look at the area where the OP indicates and have oil treatment applied if necessary.

Follow the lining all the way down and under the door itself with a good flashlight.