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Potential-controlled polarization methods can cause large positive shifts of the breakdown potential because of induction effect. The latter gives rise to current hysteresis, which leads to large unpredictable charge densities, which leads to poor accuracy and precision in determining the protection potential Eprot. Galvanostaircase polarization (GSCP) prevents induction effect and current hysteresis; however, it is subject to voltage hysteresis, which could make the determination of Eprot difficult if not impossible. Fortunately, voltage hysteresis can be avoided easily by staying at low current levels and charge densities.
Hysteresis caused by slow electrode kinetics can give erroneous results in the cyclic potentiodynamic polarization resistance measurement. A potentiostaircase polarization method was used to eliminate hysteresis. A graphic averaging technique was developed to determine the polarization resistance of a system where the corrosion potential Ecorr and the corrosion rate were changing rapidly.
corrosion, hysteresis, polarization, current hysteresis, voltage hysteresis, corrosion monitoring, galvanostaircase polarization, potentiostaircase polarization, linear polarization, polarization resistance
Senior research associate, BASF Wyandotte Corporation, Wyandotte, MI