Rust around your windshield is often the result of poor workmanship during a previous replacement. The tools used to remove the windshield and the original adhesive often scratch what’s called the pinch weald (non-visible part of car where the glass is glued) exposing bare metal. To prevent rust, primers are available to cover the bare metal and thus preventing moisture from getting trapped. We always prime bare metal. Beware of shops that leave the bare metal unprimed in order to save time and money. It may take months or years before the rust is visible to the vehicle owner and by the time it is, it will be expensive to properly repair at your local body shop.