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Stability of permanganate conversion coating formed on ZE41 - Mg alloy at different pHs and coating times

Abstract:

The corrosion resistance of the permanganate conversion coating formed on ZE41- Mg alloy as affected by coating time and pH was studied by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and polarization methods in order to find the optimum treatment conditions. The morphology of the coated and uncoated (as-abraded) samples was analyzed with scanning electron microscope (SEM), energy dispersive X-ray (EDX) and X-ray diffraction (XRD). All corrosion tests and surface analysis were done before and after immersion in corrosive (3.5% NaCl) solution. The obtained results demonstrated that the corrosion resistance of the coated samples in neutral and acidic solutions was significantly higher than that of as-abraded alloy in the studied solutions. In addition, the results declared that the best corrosion resistance was recorded in permanganate solution of pH 7.5 at coating time 10 min.