Improving corrosion resistance of AZ91D magnesium alloy by nitrogen ion implantation

The corrosion behavior of nitrogen ton (N-2(+))-implanted AZ91D magnesium alloy (UNS M11916) in 5 wt% sodium chloride (NaCl) solution was investigated using weight-loss measurement and electrochemical techniques. Ion implantation improved corrosion resistance at doses > 1 x 10(16) ions/cm(2) (6.5 x 10(16) tons/in.(2)). At doses of 5 x 10(16) ions/cm(2) (3.27 x 10(17) ions/in.(2)), the mean corrosion rate and maximum pitting depth reached minimums. Impedance spectra drew a capacitive semicircle at 2 x 10(16) or 5 x 10(16) ions/cm(2) (1.3 x 10(17) ions/in.(2) or 3.2 x 10(17) ions/in.(2)). Additional inductive loops were observed in the lower frequency of untreated or implanted specimens outside this range. The presence of the inductive loop was discussed in terms of corrosion morphology, particularly in terms of the occurrence of pitting corrosion Monitoring polarization resistance (R(p)) was shown to be useful in evaluating effects of ion implantation.