Degradation effects of maritime atmosphere on metallic components of solar collectors

The influence of mixed maritime atmosphere on the degradation of metallic components of exposed solar thermal collectors was studied. Corrosion measurements of standard metal samples (unalloyed carbon steel, zinc, copper and aluminum) were performed according to ISO 9226/1992 and ISO 9223/2012 with two different test set-ups; one in the open atmosphere, the other inside a commercial flat-plate thermal collector. Moreover, the influence of defined microclimatic conditions inside the thermal collector on the durability of different absorber surfaces was investigated. The results show extremely high corrosion rates in the open atmosphere for all exposed metals in contrast to the samples inside the solar thermal collector, where high corrosivity was only detected for amorphous metals. The results of optical measurements of the exposed absorber samples show a very good stability of the materials. Additionally, different analytical methods were used for the characterization of corrosion products. This information can be used for the optimization of accelerated aging tests for absorber materials with respect to corrosive environment and salt content.