intercoat

An intercoat, also called an intermediate coat or bonding coat, is a coating layer applied between a primer and a topcoat in a multilayer coating system. Its primary role is to improve adhesion between layers and to provide properties not offered by the primer or the topcoat alone. Intercoats can also serve as sealers, moisture barriers, and fillers for minor surface imperfections, and they may help to control solvent migration and color uniformity.

Intercoat formulations vary by industry and application. They are typically designed to be compatible with both the primer beneath and the topcoat above. Common chemistries include epoxy-based intercoats, polyurethane or acrylic-based intercoats, and waterborne or solvent-borne systems. Some systems use a colorless intercoat primer to serve as a bonding layer, while others employ an intercoat clear or pigmented midcoat in basecoat/clearcoat architectures.

Applications are widespread: automotive refinishing, marine finishes, metal fabrications, and wood products often use an intercoat to bridge between primer and topcoat, improve corrosion resistance, and achieve a smooth, uniform final appearance. In wood finishes, intercoats can reduce grain raising and help compensate for surface imperfections.

Application and processing notes: surface preparation must be compatible with both the underlying primer and the subsequent topcoat. After curing, the intercoat is usually sanded to provide a mechanical key for the topcoat and to remove any imperfections. Drying times and recoat windows vary by formulation and environmental conditions.

In summary, an intercoat is a deliberate, intermediate layer in coating systems that enhances adhesion, protection, and surface finish by bridging primer and topcoat interfaces.