Corrosion resists Ni, Co co-pigmented nanoporous anodized alumina as spectral selective coating structure for solar thermal applications

Ni–Co pigmented anodized alumina as spectrally selective coating is realized using electrodeposition. Ni and Co metals are pigmented into nanoporous alumina by the reduction of metallic ion from aqueous solution. The measured spectral absorptance and thermal emittance are ∼0.90 ± 0.05 and 0.14 ± 0.04, in 0.2–2.5 μm and 2.5–25 μm wavelength window, respectively for the optimized Ni–Co co-pigmented alumina spectrally selective coatings. The optimized solar selective coating samples are heat treated in open environmental condition at 300 °C for 100 h to evaluate their thermal stability. The absorptance is nearly unaffected after heat treatment, whereas slight enhancement in thermal emittance is observed as compared to the unheated sample. After thermal evaluation, corrosion characteristics are also evaluated and observed that Ni–Co co-pigmented coatings are more corrosion resistant than anodized alumina structures, suggesting that these co-pigmented solar selective coating may be suitable for mid temperature absorbers in ambient conditions.