In this work, we demonstrate that the use of the scanning electrochemical microscopy in transient mode allows the investigation of adsorbate intermediates at a polarized interface. Two different systems were studied. In the case of a competitive adsorption involving halide and hydrogen, the contribution of each element was monitored independently. Interestingly, the simultaneous measurement of the electrochemical impedance allowed the complex differential capacitance for each adsorbed species to be calculated. In the case of the iron dissolution, the formation of a monovalent Fe species was evidenced allowing to discriminate between different dissolution mechanisms previously described in the literature. (C) 2014 Elsevier Ltd. All rights reserved.