Corrosion protection performance of novel hybrid polyaniline/sol–gel coatings on an aluminium 2024 alloy in neutral, alkaline and acidic solutions

In this study the corrosion performance of a novel coating, consisting of a combination of silica sol-gel and conductive polymer, in 3.5% NaCl at different pH levels is presented. Electrochemical Impedance Spectroscopy showed the impedance of the coating remained stable for up to 24 months in neutral 3.5% NaCl solution. No corrosion or delamination was observed after 500 h in salt spray tests and Scanning Vibrating Electrode Technique tests showed the coating exhibited a "self healing" property. The surface morphology was characterised by Scanning Electron Microscopy and the mechanical properties, notably adhesion, were studied using pull off and cross cut techniques.