Surface passivation of AZNd Mg alloy with Pr(NO3)(3) is studied using scanning electrochemical microscopy (SECM) in surface generation/tip collection (SG/TC) and AC modes. Corrosion protection afforded by the Pr treatment and the degradation mechanism in a simulated biological environment was examined on a local scale and compared with non-treated AZNd. SG/TC mode results revealed a drastic decrease in H-2 evolution due to the Pr treatment. Mapping the local insulating characteristics using AC SECM showed higher conductivity of the surface where H-2 evolution was most favorable. (C) 2014 Elsevier B.V. All rights reserved.