This specification covers the performance and qualification requirements for rigid exterior two component (2K) urethane clearcoat systems used over high solids solventborne basecoats. Typical volume solids as sprayed are 45% to 50% for basecoat and 50% to 60% for clearcoat. This topcoat system is intended for rigid or semi-rigid substrates painted outside of the assembly plants.

Material Description. Basecoat components of these systems are typically one component (1K) (solvent) acrylic melamine. Clearcoat components of these systems are 2K (solvent) urethane or urethane blends. Each combination of specific basecoat and clearcoat must be tested and approved as basecoat/clearcoat system. The individual components are not interchangeable. In addition, the topcoat system must meet qualifications set forth in this specification and those shown on engineering drawings. Validation testing for plant specific layering, ancillary materials, and processing must be conducted prior to release.

Qualified to this Material Specification. Each combination of specific basecoat and clearcoat must be tested and approved as a basecoat/clearcoat topcoat system. The individual components are not interchangeable. This specification shall be used in conjunction with the GMW14797: Approved Paint on Plastic System (APOPS), a section of the GM Materials Approval Source List, which lists the approved substrate, cleaning, priming, and topcoat combinations or GMW14669: Organic Coating Performance for Exterior and Interior Metallic Components. In addition, the topcoat system is part of the total coating system and must meet qualifications set forth in this specification and those shown on engineering drawings for appearance and durability.

Symbols. Not applicable.

Applicability. These topcoats are designed to be applied over a baked primer.

Remarks. Not applicable.