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.

Chemical characteristics, mechanical and thermo-optical properties of black anodic films prepared on 7175 aluminium alloy for space applications

“…To provide specific superficial properties (against corrosion or wearing for example), many surface treatments are available. In particular, different colouring processes can be used to confer a black colour to the anodic films prepared on aluminium parts: incorporation of organic dyes [1,2], electrocolouring with metals [3][4][5][6], anodic polymerization [7], co-deposition of organocomplex anions [8] or impregnation by coloured mineral precipitates, such as cobalt sulphide. This last process is usually limited to applications requiring thermal stability of the dyes, i.e.…”

Tuning Optical Properties of Photonic Crystal of Anodic Alumina and the Influence of Electrodeposition

“…To absorb the light, nickel is always used for the black coloring process, as in thermal energy production from solar energy. 15 In the present work, tin/nickel is used for the deposition in the porous alumina. 16 With enough deposition time, the reflection from Al substrate can be suppressed seriously.…”