What must be applied to existing flashing when reusing it to ensure proper adhesion?

When reusing existing flashing, applying primer is essential to ensure proper adhesion. The role of primer in this context is to create a suitable surface for subsequent materials, such as sealants or paints, to adhere to more effectively. Flashing, being exposed to the elements, can accumulate dirt, dust, and oxidation over time, which can inhibit the proper bonding of any material applied over it.

Applying primer helps to prepare the surface by promoting adhesion and ensuring that any subsequent coatings can seamlessly bond to the flashing material. This leads to enhanced durability and reduces the risk of leaks or failures in the flashing system. Proper surface preparation with primer is a crucial step in construction and renovation processes where existing materials are reused.

Other options mentioned, while they may play a role in different contexts, do not specifically address the need for creating a proper bonding surface in the same way that primer does. For example, a sealer may help protect the surface but is not primarily intended to promote adhesion. Similarly, paint is more for aesthetic purposes rather than establishing a foundational bond, and adhesive is typically used for bonding materials rather than preparing surfaces.