Abstract
A composite ceramic coating containing Al 2O 3–ZrO 2–Y 2O 3 was successfully prepared on AZ91D magnesium alloy by plasma electrolytic oxidation (PEO) technique in an alkaline aluminate electrolyte. The morphology, elemental and phase composition, corrosion behavior and thermal stability of the uncoated and coated samples were studied by environmental scanning electron microscopy (ESEM), energy dispersive X-ray spectrometer (EDS), X-ray diffractometer (XRD), electrochemical corrosion test, high temperature oxidation test and thermal shock test. The results showed that the composite ceramic coating was composed of Al 2O 3, c-ZrO 2, t-ZrO 2, Y 2O 3 and some magnesium compounds, such as MgO, MgF 2 and MgAl 2O 4. After PEO treatment, the corrosion potential of AZ91D alloy was increased and the corrosion current density was significantly reduced. Besides, the coated magnesium alloys also showed excellent high temperature oxidation resistance and thermal shock resistance at 500 °C environment.
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