VASP Rp determination – Corrosion- Application Note 36Latest updated: May 6, 2020
Variable Amplitude Sinusoidal microPolarization technique is an electrochemical protocol based on EIS measurements using low voltage amplitude perturbation. Like the Tafel plot technique, the VASP allows the determination of the corrosion rate and Tafel parameters of a corrosion system without sample surface destruction. In this note, the VASP technique is introduced. The corrosion parameters of a pure Nickel sample in acid media were determined using VASP technique. The obtained results were compared with those obtained with Tafel plot technique.
Variable Amplitude Sinusoidal micropolarization technique (VASP) is a new electrochemical method integrated into EC-Lab® and EC-Lab Express®. It is based on an electrochemical impedance measurement that allows the study of corrosion mechanisms by the determination of Tafel parameters, and the corrosion current.
The VASP technique consists of determining the change of the measured polarization resistance Rp with the potential amplitude variation. Rp is determined by Electrochemical Impedance spectroscopy measurements at a fixed and low enough frequency fs. fs determination is defined in the next paragraph.
The VASP experiment is performed by applying a sinusoidal electrical potential EWE(t):
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