Permanganate is a much more effective surface passivator of Mg alloys since these ions are readily involved in redox processes on the surface, resulting in the formation of the insoluble film of MnO2 and hydrated MnOOH. By creating a protective insoluble coating over the active surface areas, permanganate ions in aqueous conditions slow down the corrosion of the alloys under investigation. These processes can be summarized by equations: Note that Mn(IV) species are stable in aqueous solutions, so it can be expected that formed MnOOH can be oxidized to MnO2 (or its hydrated forms) following the equation (Fig. ):