24 min read

CASP Rp determination – Corrosion – Application Note 37

Latest updated: May 6, 2020


The Constant Amplitude Sinusoidal microPolarization (CASP) technique is an innovative protocol for the determination of corrosion parameters with EC-lab software. In this note, the theory and the equations involved in the CASP technique were introduced. The results of the characterization of Nickel in acidic media using CASP are given here. The results were also compared with the corrosion rate and Tafel parameters obtained with Tafel Plot technique. It was shown that the corrosion parameters obtained with VASP technique are similar to those obtained with Tafel plot technique with a significantly shorter time and less disturbance of the corrosion system.



Two classical methods based on the Stern relation are commonly used to determine the uniform corrosion current Icorr of a metal in contact with an aggressive solution:

1. Using the Tafel method [1], which requires to apply significantly large overpotentials (typically over +/-100 mV).
2. Determining the polarization resistance Rp [1] by applying a small sinusoidal potential perturbation and using the SternGeary relation, which requires to know the Tafel parameters.


To view the entire application note please click the download button below.