Investigation of surface composition of electrodeposited black chrome coatings by X-ray photoelectron spectroscopy

Solar selective black chromium coating was electrodeposited on pre-treated electroformed nickel substrates from a hexavalent chromium containing bath. The composition of the film was investigated before and after annealing at 400 °C for different durations. In the as-deposited condition, the surface of the film was found to have trivalent chromium hydroxide and chromium in the chromate form contrary to previous studies which report the presence of hydroxides and metallic chromium. However in the present study, no evidence for metallic chromium was found. The major component, chromium hydroxide, was converted to Cr2O3 on annealing at 400 °C with the loss of water vapor. The chromate form remains but with a lowered concentration.