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In this study, aluminum coatings were prepared by dc magnetron sputtering on AZ31B magnesium alloy. The influence of sputtering parameters (include sputtering current, argon pressure, and deposition time) on corrosion behavior was investigated by potentiodynamic polarization tests in 3.5 % NaCl solution. The corrosion morphology was examined in detail by scanning electron microscopy and optical microscopy, respectively. It was found that the corrosion current density of magnesium alloy with aluminum coating was 2–3 orders of magnitude less than that of bare alloy. The corrosion potential with aluminum coating had been positive shift. The corrosion resistance of the coatings was strongly affected by its structure and residual stress, which depended on the process condition. Severe corrosion will occur after the aluminum coating is damaged due to the interaction of galvanic corrosion and other corrosion forms.