In-situ monitoring of pitting corrosion of Q235 carbon steel by electrochemical noise: Wavelet and recurrence quantification analysis

Abstract

Abstract Pitting corrosion of Q235 carbon steel in 0.25 M NaHCO3 with different concentrations of chloride ions was in-situ monitored by electrochemical noise (EN) technique, and the EN signals were analyzed by transient shape analysis, wavelet analysis and recurrence quantification analysis (RQA). Four typical electrochemical current noise (ECN) transients corresponding to different pitting stages including passivation, random metastable pitting, transition stage and stable pitting stage were observed. It was found that the RQA parameters, recurrence rate (R) and determinism (D), show the ability to separate the four ECN transients, while wavelet parameter show poor ability to distinguish the ECN transients arising from random metastable pitting and transition stage. Furthermore, the ratio of D and R (η) was proposed to monitor the pitting corrosion. The average value of η for the passivation and random metastable pitting is 1.88 and 1.63, and it gradually increases to around 6 during the transition stage and early stable pitting stage, the value slightly decreased to 4.16 at the late stable pitting stage. The detailed relationship between the EN characteristic parameters and dynamic process of pitting corrosion is discussed.