The coupling current map of an Fe specimen partially covered with Zn coating was traced in an atmospheric corrosion test by using a 100-channel electrodes coupling current measurement system. The time series of the coupling current map of the iron surface in an arrangement of a 10 × 10 matrix clearly revealed transition of the corrosion protection mechanism of Fe from sacrificial protection by anodic dissolution of Zn to inhibitory protection by the Zn corrosion product covering the Fe surface. Corrosion products on each electrode were also identified by using microscopic Raman spectroscopy. In the sacrificial protection period, Zn ions extended to the area around the Zn-coating and formed a hydrozincite layer due to absorption of CO 2 in the solution alkalized by the cathodic oxygen reduction. After complete depletion of the Zn coating, corrosion of Fe could be inhibited by the hydrozincite and simonkolleite layer covering the Fe surface but not by the zincite layer.