The influence of hydrofluoric acid doped polyaniline on the protective performance of a mg-rich epoxy coating on AZ91D magnesium alloy

Hydrofluoric acid doped PANI (PANI-HF) particles were added to a magnesium (Mg)-rich primer (MRP) on AZ91D Mg alloy and the influence of the particles on the primer was investigated. The optimal PANI-HF particle content was 1 wt.%. These particles improved the electrical contact between Mg particles and the AZ91D substrate, thereby enhancing the cathodic protection. Subsequently, the products of Mg particles (MgO and MgF2) precipitated in the coating and improved the barrier effects. Moreover, PANI captured some chloride ions, thereby reducing degradation of the coating. Eventually, the protective film formed on the AZ91D substrate blocked the electrolyte permeation, retarding the corrosion of the substrate.