Due to its potential use as selective surface in solar thermal absorbers, cobalt has been electrodeposited into porous alumina obtained by anodization of aluminum sheet. A 3(2) factorial design has been applied to find out the effects of the electrochemical variables, electrodeposition time and applied cell potential, on optical properties and to optimize the solar energy selectivity of the obtained surfaces. Effective-medium optical models have been used to reproduce their reflectance spectra and to estimate the thickness of the different layers that form the selective surface. (C) 2014 Elsevier B.V. All rights reserved.