What characteristic is essential for a successful primer coat?

A successful primer coat must have strong adhesion to the substrate. This characteristic is critical because the primer serves as the foundation for subsequent layers of paint. Good adhesion ensures that the primer properly bonds to the surface, whether it is metal, plastic, or another material, preventing issues like peeling or flaking in the future. When the primer adheres well, it helps seal the surface and allows for better application of the topcoats, leading to a more durable and visually appealing finish.

While other characteristics like the ability to hide imperfections or rapid drying time are also valuable in a primer, they are secondary to the primary role of adhesion. Without proper adhesion, even a primer with excellent hiding capabilities or quick drying properties may fail to perform effectively, resulting in poor overall paint quality and durability.