What is the primary function of the intercoat layer (tie coat) in a coating system?

• A. UV protection
• B. Improve intercoat adhesion and barrier properties
• C. Color uniformity
• D. Cure acceleration

Answer: (B)

Intercoat layers, or tie coats, are placed between the primer and the topcoat to bridge adhesion and enhance the system’s barrier performance. They create a chemically compatible surface for the subsequent coat and help accommodate differences in surface energy and hardness between layers. This improves bonding and creates a more uniform, sealed interface, which reduces pathways for water, oxygen, and chlorides to reach the substrate. As a result, the overall corrosion protection is stronger because moisture and corrosive species have a harder time penetrating through the coating stack. UV protection is mainly provided by UV stabilizers in the topcoat, color uniformity depends on pigment dispersion in the topcoat and film thickness, and cure acceleration is controlled by formulation choices for the coat chemistry rather than the tie coat’s primary role.