What is the main purpose of tie coats in painting?

The main purpose of tie coats in painting is to serve as a transitional layer between a primer or undercoat and the finish coat. Tie coats are specifically formulated to enhance adhesion between different types of coatings and to ensure that the finish coat applies smoothly and evenly over the surface.

Using a tie coat allows for better integration of the layers, reducing the risk of issues such as peeling or flaking that can occur if there is insufficient bonding between the layers. By providing this crucial transition, tie coats help to achieve a more durable and aesthetic final result in paint applications.

While other coatings serve different purposes—such as providing a glossy finish, preventing rust, or acting as a protective barrier—tie coats are uniquely positioned to facilitate the connection between primer and finish, making option C the most accurate choice in this context.