The results of the EDX analysis (Table ) confirmed that the formed surface films primarily contain magnesium, most probably in the form of oxide and hydroxide. Aluminum was also observed in rather high amounts (up to 2.6 at.%) at the majority of examined spots. After 24 h of exposure to the corrosive environment, the oxygen content in the composition of surface films increased, which may be due to the formation of a thick layer of oxide-hydroxide passive films.