Chemical reactivation of exterior decorative aerospace topcoats

Exterior aerospace topcoats are typically highly cross-linked polyurethane based paints designed to be resistant to UV degradation with a high level of adhesion required during all aspects of flight. These topcoats are also designed to be resistant and inert to a variety of aggressive solvents and airplane fluids. Consequently, during processing, a topcoat surface can be inert to the reception of the next topcoat layer. Proper surface preparation of each paint layer prior to the application of the next is critical for ensuring adequate adhesion. Historically, the only viable method to prevent de-bonding of cured paints has been to mechanically abrade (sand) prior to the application of subsequent coating layers. However, sanding is an economically hazardous process, adds process flow time, and produces contamination. In addition, sanding intricate stencil lettering in most cases is not feasible without tearing the stencil material and/or leaving visible scratches in the areas immediately surrounding the stencil markings. Chemical reactivation using a newly developed alkoxide-based chemical reactivator has proven to be a viable alternative to scuff sanding and has been successfully implemented on multiple aerospace platforms. This paper discusses the properties and application process of aerospace decorative livery, the mechanism and tests available for rain erosion durability and the performance of paint layers bonded by the chemical reactivation process.