Corrosion Resistance of Alcrno-Based Solar Selective Absorbing Coating Prepared By Cathodic Arc Plating
Solar selective absorbing coating is core material in solar thermal plant system, and usually operates in atmosphere with no shield. So, corrosion resistance is important to the coating. AlCrNO-based solar selective absorbing coatings prepared by cathodic arc plating with absorptance / emittance of 0.94 / 0.20, which were reported in previous paper, were tested the corrosion resistance in H2SO4 solution (pH=4.0) for 24 hours, in Na2CO3 solution (pH=9.5) for 24 hours, and in neutral salt spraying test (NSST) box for 100 hours, respectively. The results showed that the selective absorptive of all samples changed little after these tests. The absorptance / emittance of the coatings after these tested were 0.94 / 0.22 for acid corrosion test, 0.94 / 0.19 for alkaline corrosion test, and 0.94 / 0.21 for NSST. According to these results, the emittances of the samples after acid corrosion and NSST increased. The main reason for the increase of the emittances was due to the holes and the cracks resulting from the broken of the macro-droplets which leaded to the increase of the occasion of reflection in the mid infrared wavelength range. Therefore, reduce the number of macro-droplets of the coatings is a method to ensure the optical performance stability. After all, according to the performance criterion, all the samples possess of sound corrosion resistance and are capable of applying in atmosphere.
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