An investigation on the optimisation of electrochemically pigmented aluminium oxide selective collector coatings

In order to produce selective coatings on aluminium substrates to be used as absorber plates in high efficiency solar collectors, nickel pigmentation has been applied to anodically oxidized surfaces. Optical and structural properties of electrochemically formed aluminium oxide films as function of electrolysis conditions such as, applied current, pH, temperature and concentration of metal ions have been examined using electron spectroscopy and scanning electron microscopy. The optimisation of the absorptivity/emissivity ratio of the surfaces in terms of preparation conditions is described. Nickel pigmentation of porous aluminum surfaces was also investigated as a function of electrochemical pigmentation conditions. Mechanisms contributing to selectivity in anodically produced oxides and electrodeposits are discussed. Copyright (C) 1996 Published by Elsevier Science Ltd.