Influence of the thickness and roughness of polyaniline coatings on corrosion protection of AA7075 aluminum alloy

Polyaniline coatings of various controlled thicknesses are applied to 7075-T6 aluminum alloy substrates and evaluated for their corrosion protection ability in a corrosive saline environment using electrochemical techniques. The coating thicknesses are in the range of approximately 5 to 35 pm and they increase linearly with increasing quantities of PANI solution deposited on the substrate. The relationship between the coating thickness, roughness, and hydrophilicity is examined. Coatings ranging from 12 to 23 pm in thickness have the lowest roughness values and highest contact angles with water. The PANI-coated 7075 alloy electrodes with low roughness and high contact angles show better corrosion protection properties in saline solution (3.5% NaCl), as determined by electrochemical impedance spectroscopy (EIS) and voltammetric polarization measurements. Scanning electronic microscopy (SEM) images demonstrate the homogenous surface morphology of the PANI coatings on the micrometer scale. Even after prolonged exposure to corrosive media, no cracks were found. (C) 2017 Elsevier Ltd. All rights reserved.