Comprehending the mechanism of corrosion film growth on the anode in electrolytes is a foundation in the tailoring of a desirable delayed action in magnesium manganese dioxide (Mg/MnO2) primary batteries. The formation and growth evolution of the corrosion film on AZ63 magnesium alloys in 2 mol L-1 MgSO4 aqueous solution was investigated by scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. Results indicate that corrosion preferentially occurred on the a phase adjacent to the 13 phase of the alloy before spreading to the area away from the beta phase. The beta phase acted as a micro cathode that accelerates the corrosion dissolution. The film consisted of a base film and mosaic particles with amorphous mixed compositions of MgO, Mg(OH)(2), (MgCO3)(4) center dot Mg(OH)(2) center dot 4H(2)O, and Mg(OH)(2) center dot 2MgSO(4). The formation and growth of the film on the AZ63 magnesium can be divided into three stages: film formation, film composition transformation, and film structure breakdown. A film growth model was also proposed for interpreting the corrosion evolution of the AZ63 alloy. (C) 2017 The Electrochemical Society. All rights reserved.