Stop in for a cup of coffee

I have used this as a temporary fix. Suppose it would do the job. My big concern with adding anything like this is trapping dirt and moisture and making it worse.
Permatex Silicone Windshield/Glass Sealer, 1.5-oz.: Model# 81730 | True Value

I agree, I don't want to seal it, I just want some kind of rust-inhibitor I can drizzle into that gap and let it flow into the space. That is one of ways they tell you on the can that you can use Por-15.