Non-sparking anodization process of AZ91D magnesium alloy under low AC voltage

► Four different processes appear on magnesium alloys with applied voltage increase. ► Non-sparking film formation process occurred in the range of 6-10 V AC. ► The film was composed of Mg2SiO4 with a stable growth rate in 30 min. ► Film growth was a balance of electrochemical dissolution and chemical deposition.