The high-purity magnesium alloy specimens prepared by applying die-cast ([1]) paint and various types of surface treatments, and then the corrosion resistance of practical coating materials after ten-year outdoor exposure tests was evaluated. These tests were performed at the Choshi (long. 140 degrees 45'E, lat. 35 degrees 43'N), the Asahikawa (long. 142 degrees 18'E, lat. 43 degrees 47'N), and the Miyakojima (long. 125 degrees 20' E, lat. 24 degrees 44' N) Exposure Laboratories of the Japan Weathering Test Center. The environmental factors generally believed to be associated with corrosion mechanisms (temperature, humidity, precipitation, wetness time, solar and UV radiation, and concentration of chloride and sulfur oxide) were measured. Evaluation of the adhesion of paint and corrosion resistance, chromate and anodic oxide films were superior as pretreatment paint films on AZ91D magnesium alloys; these films were comparable to paint-coated ADC 12 aluminum alloys.