A new criterion to determine the critical pitting temperature (CPT) based on electrochemical noise measurement

Electrochemical noise (EN) was recorded during the temperature linear scanning period and analyzed using noise thermammetry method. The transition point, separating the Arrhenius plot into two regions, was observed. Below this point, the activation energy of material converse to negative and the corrosion events become spontaneous process. Therefore, this transition point can be as a criterion for the determination of CPT. The effect of inhibitor concentration, surface roughness and ageing time on the CPT were also investigated by means of EN method with comparison of potentiostatic results. These demonstrate the universality and measurement precision of this new criterion.

► Electrochemical noise technique was applied on the determination of critical pitting temperature.
► Electrochemical noise data was analyzed by noise thermammetry method based on Arrhenius’ law.
► A new criterion with explicit physical meaning was founded.
► The new criterion shows good precision and universality.