Analysis of the dynamics of Intergranular corrosion process of sensitised 304 stainless steel using recurrence plots

This study presents the assessment of the dynamics of intergranular corrosion of austenitic stainless steel with different degrees of sensitization through the analysis of electrochemical current noise signals. Samples of S30400 stainless steel were aged at 923 K for 50, 250 and 1,000 min before being quenched in water. The double Loop Electrochemical Potentiokinetic Reactivation test was applied to assess the degree of sensitization. The electrochemical noise data were analysed using a novel mathematical tool named Recurrence Plots (RP). This method allowed us to assess the dynamics of the intergranular corrosion process of the steel in a H2SO4 + KSCN solution at room temperature. The study was conducted using a recurrence quantification analysis (RQA) from which it was possible to determine the percent of recurrence (%R), the percent of determinism (%D) and the information Entropy of the corrosion process. It was found that these parameters increased with the sensitisation intensity, which indicates that sensitisation induced a more deterministic dynamics on the electrochemical process.