Polyhedral oligomeric silsesquioxanes as protective monolayer coatings against the high-temperature corrosion of concentrating solar power absorber surfaces

The third generation of concentrating solar power (CSP) hybrid absorbers with enhanced solar absorptance and low thermal emittance (spectrally selective) is designed to have a high solar-to-thermal energy conversion efficiency, in spite of robust, long-term resistance to environmental loads. In this study, we report on the deposition, testing, and antioxidation properties of ultra-thin (1–3 nm) mono-, di-, and tri-layers of hybrid organic‒inorganic polyhedral oligomeric silsesquioxanes (POSS) on Inconel 617. The latter is a well-known metal alloy, which is used as a CSP absorber material. Ultra-thin POSS layers were prepared by Langmuir‒Blodgett (LB) deposition. After deposition, the detailed signature characteristics of the POSS monolayer were investigated using X-ray photoelectron spectroscopy (XPS), infrared reflection‒absorption spectroscopy (IRRAS), and contact angle measurements. The XPS results with element concentration profiles reveal that the LB method enables the formation of a dense ultra-thin POSS coating on the Inconel surface, which eventually improves the antioxidation properties. To further test the corrosion resistance improvement of the developed coatings, electrochemical impedance spectroscopy (EIS) and potentiodynamic tests were performed in 0.5 M NaCl solution. The as-obtained data were fitted with the corresponding equivalent circuit, which shows an increased charge transfer resistance (R_ct) for coated samples. Tafel polarization plots show suppressed cathodic and anodic reaction rates for samples coated with ultra-thin POSS coatings. We envision that such coatings will have significant potential as a primer for spectrally selective absorber coatings for CSP technology.