The corrosion behavior of heat treated AZ91D Mg alloy and ZrO2 and ZrN coated AZ91D Mg alloy was examined by potentiodynamic polarization test. The corrosion properties were examined by immersion of the samples in NaCl solution for 6 h, 24 h, and 48 h, respectively. The surface morphology of the samples before and after erosion was analyzed. SEM and XRD revealed the formation of white deposits that may be magnesium hydroxide. The NaCl solution causes corrosion of the magnesium compound and the coated surface. From the Tefel plots, the Rp value of the coated sample was higher than that of the heat treated compound and the result was found to be better corrosion resistance. The results showed that pit erosion increased with increasing submersion hour. The performance results of AZ91D-ZrNcoating show better corrosion properties than non-coated AZ91D Mg alloy and ZrO2 coatings.