A large building in a municipal area of the coastal United States was partially clad with aluminum panels. Due to the exterior and coastal service environment, the panels were coated with an AAMA(1) 2605-compliant fluoropolymer-based coating system. However, after installation of some of the panels, the contractor noticed an unacceptable “streaked” appearance, particularly under post-dawn and pre-dusk low-light conditions.

An investigation was undertaken to document and understand the nature of the streaked appearance. The investigation consisted of the following: 1) on-site measurement of color, gloss, and coating system thickness along the length of installed panels, 2) comparative measurements on accepted visual on-site mock-up panels, 3) observations of coating application and quality control processes at the coating applicator’s facility, and 4) laboratory analysis of the coating system color, gloss, thickness, distribution, composition as well as an evaluation of the underlying substrate. The investigation found issues with primer application that may affect long-term performance, and inconsistencies in application of the topcoat that led to the unacceptable appearance.

Subject
Primers, Coatings, Microscopy, Aluminum, Thickness measurement, Roughness, Gloss, Micrography, Surfaces, Color, Surface layers, Spreading rate, Coating systems
Keywords:
coating finish anomalies, fluoropolymer, coating application, thickness, coating uniformity
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2022
Association for Materials Protection and Performance (AMPP)
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