What is the purpose of applying a primer before painting aircraft surfaces?

The purpose of applying a primer before painting aircraft surfaces is primarily to enhance adhesion and protect against corrosion. Primer serves as a bonding layer between the metal of the aircraft and the paint, ensuring that the topcoat adheres properly and remains durable over time. Additionally, many primers contain corrosion inhibitors that help to prevent rust and deterioration of the underlying surface, which is especially important in the aviation industry where exposure to harsh environments is common. This protective layer is essential for maintaining the structural integrity and aesthetics of the aircraft over its operational lifespan.

While there are other considerations in surface preparation, such as improving the finishing process and potentially enhancing the appearance of paint, the main functionalities of primer in this context are its role in adhesion and corrosion resistance.