Thin black layers on aluminum substrate - Electrochemical synthesis and characterization

Abstract

The article presents some preliminary experimental results dealing with electrochemical synthesis and morphological, optical characterization of various types of black layers onto Al substrates, involving both inorganic metallic salts of nickel, molybdenum, and conducting polymers, respectively, polypyrrole layers. The article discusses a new procedure for direct electrodeposition of black Ni, black layers based on Mo compounds during a cathodic process as well as black composite polypyrrole films during anodic oxidation that involves an initial anodizing in nitric acid electrolyte that proved to offer a very good adherence of the metal then plated on Al surfaces. Al surface morphology evolution against applied c.d. and duration during initial anodizing was also investigated, by SEM technique. The obtained black layers are characterized by a good throwing power, homogeneity, smoothness, and adherence. Also, black layers formed by a.c. electrochemical coloring in Ag- and Ni-based solutions are discussed. Optical characterization has been also performed to evaluate their solar absorptance and thermal emittance coefficients and a comparative evaluation is presented. Copyright © 2008 John Wiley & Sons, Ltd.