What is the function of a primer in auto refinishing?

The function of a primer in auto refinishing is primarily to promote adhesion and protect the underlying material from corrosion. Primer is designed to create a bonding surface for subsequent layers of paint, ensuring that those layers adhere properly to the substrate. Without an adequate primer, paint can peel or chip away over time, as the surface it’s applied to may not provide the necessary traction or stability for long-term adhesion.

Additionally, primers often have corrosion-resistant properties that help shield the metal or other materials of the vehicle from moisture and environmental factors that can lead to rust and degradation. This protective layer is essential in maintaining the integrity of the vehicle's structure while enhancing the longevity of the finish.

The other functions mentioned in the incorrect choices, such as providing a final gloss finish, enhancing color vibrancy, or serving as a filler for scratches, are not the primary purposes of primer. Those functions are typically associated with topcoats or specialized finishing products rather than with primer itself.