Enhancement of Surface Roughness and Growth Morphology of Nanoporous Anodic Alumina from Commercially Aluminum Alloy 1050 Using Two-Step Electrochemical Polishing

This article investigates the two-step electrochemical polishing process for improving growth of nanoporous anodic aluminum oxide (AAO) from commercially low-purity (< 99.5%) aluminum alloy 1050 (AA1050) at room temperature (25 degrees C). The conventional one-step electropolishing is a vital pretreatment process before the anodic oxidation for reducing the surface roughness of high-purity (>99.99%) aluminum to promote the AAO pore structure anodized at low temperature (0 similar to 10 degrees C). The AAO pore quality is related to the surface roughness and purity of aluminum, especially the commercial aluminum alloy is much rougher than high-purity aluminum. Moreover, the high-purity aluminum is rather expensive and of low strength for practical application. Here, we propose a novel two-step electropolishing approach to improve the anodization of low-cost commercial AA1050 alloy with low purity and high roughness. The optimum electrolyte ratio and polishing time of the two-step electropolishing can effectively achieve the smooth surface for promoting AAO growth. The pore size distribution and deviation of AAO from AA1050 at 25 degrees C are enhanced from 17.1 +/- 4.90 nm with 15.62% max distribution (one-step electropolishing) to 23.5 +/- 3.74 nm with 19.35% max distribution (two-step electropolishing) at stable time-dependent current evolution. (C) 2018 The Electrochemical Society.