Assessment of the dynamics of corrosion fatigue crack initiation applying recurrence plots to the analysis of electrochemical noise data

Electrochemical current oscillations generated during the early stages of corrosion fatigue damage (CFD) were analysed applying recurrence plots. "This novel analysis tool allowed us to assess changes in the dynamics of the CFD process, differentiating pure electrochemical process like of pitting corrosion (PC) from the corrosion fatigue crack formation and initial growth". The dynamics of CFD initiation was characterized by determining changes in the selected recurrence quantification analysis (RQA) parameter: the percentage of determinism (%D). A significant contribution of this work is that it was possible to separate through changes in %D as a function of the number of cycles (N), the electrochemical process of pitting corrosion from the corrosion fatigue crack initiation and growth, which has a random nature and involved low values of %D of around 5%. A subsequent augment of the %D to values from 75% to 95% with the increase of N could be related to the short fatigue crack arrest. The increment of %D indicates that the electrochemical pitting corrosion process was the predominant contribution to the current oscillations.