Abstract
Germanides are an interesting class of two-component systems which consist of metal and germanium. They are similar in their structure with silicides but have the specific properties. The target of the investigation was finding the main anodic electrochemical behaviour mechanisms for magnesium germanide Mn5Ge3 in an Na2SO4 aqueous solution.Electrochemical behaviour of manganese germanide obtained by Czochralski method was investigated by polarization curves and electrochemical impedance spectroscopy methods and accomplished by microscopy data. Individual manganese and germanium were investigated in the same way for comparison. It was established that in the anodic oxidation process germanium is the potential-determining component. The passivation process associated with the formation of surface oxide films was accomplished by the current density oscillations appearing due to the bad adhesion of oxide film to the surface of the sample, its imperfection and discontinuity. The nature of oxide film formed in the polarization process waspartially established. The dependence of the anodic behaviour of the sample on the sulphate concentration was established: in the diluted solutions the passivation occurs at more positive potentials than in the concentrated. This phenomenon can be explained by the different mechanisms of anodic oxidation in the solutions of different concentrations.
Highlights
In the modern world, much attention is paid to the search for new materials with high corrosion resistance over a wide range of aggressive media
There is an array of data obtained as a result of the study of electrochemical processes occurring on the silicide Mn5Si3 and manganese monosilicide MnSi in acidic electrolytes [5,6,7]
A comparative study of the anodic behaviour of manganese, germanium, and manganese germanide in a 0.5 M Na2SO4 solution was carried out by the polarisation curve method (Fig. 1)
Summary
Much attention is paid to the search for new materials with high corrosion resistance over a wide range of aggressive media. Such materials are transition metal silicides [1, 2]. The study of germanides of the same metals, which are close to silicides in structure [3] but do not have a high resistance to corrosion, may be interesting mainly due to the elucidation of the mechanism of dissolution of systems consisting of several components, differ by their physical and chemical properties. The publications mainly contain data on the electrochemical and corrosive behaviour of metal silicides of various compositions [10,11,12,13,14], while such studies for germanides are less common [15, 16]
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