Characterization of any corroding system begins with determining its corrosion potential and rate. These two values serve as a preliminary measure of its surface passivation and kinetic activity which may then be investigated in more detail using local electrochemical or spectroscopic techniques. The potentiodynamic polarization curve (PDP) is the most common technique for simultaneous extraction of these two values, since it provides additional kinetic information in the form of Tafel slopes and can further be used to measure the pitting potential of a system. In the past, numerical analysis of these curves has proven challenging where mass transport limitations influence the currents measured. In this presentation we discuss a finite element model that has been developed to analyse the kinetics of corroding magnesium and steel alloys during PDP’s where both activation and diffusion-controlled currents are present. Furthermore, the origins of the mass transport limitations present in these systems have been investigated in more detail through an analysis of the concentration profiles involved.