Durability of different selective solar absorber coatings in environments with different corrosivity

The degradation and durability of different selective solar absorbers surfaces in outdoor exposure testing (OET) sites with different atmospheric corrosivity (maritime/industrial and urban atmospheres) were investigated for the optimization of accelerated aging tests to the qualification in terms of durability of selective solar absorber coatings in different environments. Two Outdoor Exposure Testing (OET) sites were constructed, the climate was characterized and the atmospheric corrosivity categories were determined by corrosion rate measurements of standard specimens (carbon steel, zinc, copper and aluminium) during 12 months, according to ISO 9223, ISO 9225 and ISO 9226:2012. Two Physical Vapour Deposition (PVD) coatings (commercially available) and three paint coatings (commercially available) were also exposed in the two OET sites with evaluation of degradation after 1, 2, 4, 6, 9 and 12 months of exposure in terms of optical properties (solar absorptance and thermal emittance), morphology and chemical evaluation (SEM/EDS and XRD). The selective solar absorber surfaces submitted to OET sites for one year were ranked according to their performance in terms of optical properties and corrosion over time. The results obtained show the relevance of outdoor exposure testing sites, namely in places with high corrosivity as in marine and/or industrial areas as a reliable way to verify the corrosion resistance of new materials and products and the evolution of optical properties degradation of absorber surfaces in the presence of high concentration of contaminants.