Spot, Zone and Overcoating Existing Bridge Coatings. This app is a user’s guide for bridge preservation practitioners who want to spot, zone and overcoat painting projects to extend the service life of original bridge coatings. These techniques are often simpler to implement than full removal and replacement. The app describes advantages, disadvantages, site assessment, how to choose a coating system, safety considerations, surface preparation, quality assurance, inspection equipment, and more.