Scratch-resistant anticorrosion sol–gel coating for the protection of AZ31 magnesium alloy via a low temperature sol–gel route

A novel hybrid sol–gel/polyaniline coating has been developed for application onto an AZ31 magnesium alloy for corrosion protection. Electrochemical Impedance Spectroscopy in 3.5 wt% NaCl and diluted Harrison’s solutions, along with salt spray tests showed that the coating possesses excellent corrosion resistance. The hybrid coating was modified by doping with silica nanoparticles (for scratch resistance) and cured at a low temperature of 75 °C. Whilst conventional sol–gel methods tend to limit the coating thickness values up to 10 μm, the new hybrid sol–gel/polyaniline system presented here allows thick coatings to be deposited, in this case, around 50–60 μm.