Influence of Plasma Electrolytic Oxidation on Corrosion Characteristics of Friction Stir Welded ZM21 Magnesium Alloy
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Magnesium alloys and their welds are prone to severe corrosion and require corrosion prevention treatment before being used for engineering applications. In this study ZM21 magnesium alloy plates were friction stir welded and subjected to surface conversion treatment using Plasma Electrolytic Oxidation (PEO). Base material and welds with and without PEO coatings were characterized by optical microscopy and scanning electron microscopy (SEM). Electrochemical corrosion behavior of PEO coated and uncoated specimens were evaluated by potentiodynamic polarization tests (PDP) and electrochemical impedance spectroscopy (EIS). It has been concluded that PEO treatment results in significant improvement of corrosion resistance of both base material and friction stir welds of ZM21 magnesium alloy.
Keywords:ZM21 magnesium alloy friction stir welding (FSW) plasma electrolytic oxidation (PEO) corrosion structural applications
The authors are grateful to Dr. G. Madhusudhan Reddy, Scientist “H”, Defense Metallurgical & Research Labs, Hyderabad, for making the friction stir welds at Material Joining Laboratory.