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.
A building, partially clad in fluoropolymer coated aluminum panels, was observed to have an aesthetically unacceptable appearance while still under construction. Once installed on the building, many of the panels exhibited a vertical streaked appearance under certain conditions. When the panels were at ground level, or when the sun was bright, the streaky appearance was not noticeable. However, in conditions of low light, such as during early morning, dusk, or on cloudy days the streaky appearance was reported to become apparent. A visual mock-up, consisting of multiple coated panels that had been approved by the architect as a guide to the anticipated appearance were also present on-site as a reference. This visual mock-up was used as a reference for acceptable appearance of the coated panels.
Up-close observations and limited testing including thickness, color, and gloss measurements were made of the panels onsite in the installed condition. Selected panels were removed from the site for laboratory evaluations including thickness, color, gloss, roughness and microscopical evaluations. In addition to the on-site and laboratory evaluations, visits were made to the coating applicator to observe their processes.