potentiodünaamiline

Potentiodünaamiline polarization, or potentiodynamic polarization, is an electrochemical technique used to characterize the corrosion behavior and kinetics of metals and alloys. It involves sweeping the electrode potential linearly with time while recording the resulting current, typically in a three-electrode cell with a working electrode, a reference electrode, and a counter electrode, controlled by a potentiostat.

During a potentiodynamic experiment, the potential is scanned over a defined range in either anodic, cathodic, or both directions at a chosen scan rate (commonly 0.1–1 mV/s). The resulting current–potential relationship yields a polarization curve from which key parameters are extracted. The corrosion potential (Ecorr) and corrosion current density (icorr) reflect the thermodynamic tendency to corrode and the rate of uniform metal dissolution, respectively. The anodic and cathodic branches often display Tafel behavior, described by slopes ba and bc, enabling estimates of icorr by extrapolation. In some systems, a passive region with a low, steady current appears, and a pitting potential (Epit) or protection potential may indicate susceptibility to localized corrosion or breakdown of the passive film.

Data from potentiodynamic polarization are used to estimate corrosion rates (via icorr and Faraday’s law) and to assess the effects of surface treatments, alloying, temperature, electrolyte composition, and corrosion inhibitors. The Stern–Geary relationship may be employed to relate polarization resistance to icorr. Limitations include sensitivity to scan rate, surface preparation, and environmental conditions; results may be dependent on the test window and may not fully represent long-term service behavior.