The effects of electric parameters including frequency, duty cycle, current density and final voltage on properties of anodic coatings formed on AZ91HP magnesium alloys were systematically investigated using the orthogonal experiment of four factors with three levels. The effect order of factors on the corrosion resistance of anodized Mg alloys was ranked as final voltage > frequency > duty cycle > current density, while the sequence on the coating thickness was final voltage > current density > duty cycle > frequency. The porosity of anodic coatings was increased with an increase of final voltage, but decreased with an improvement of frequency. The electric parameters applied affected the corrosion resistance mainly by influencing the coating thickness and surface morphology. (c) 2007 Elsevier B.V. All rights reserved.