Cyclic Voltammetric Study of the Pitting Corrosion Behavior of Low-Nickel Austenitic Stainless Steels in Citric Acid

The pitting corrosion behavior of AISI 202 stainless steel (SS) – a low-nickel, austenitic SS grade, was investigated by means of cyclic voltammetry (CV) technique complemented by Scanning Electron Microscopy (SEM). From the starting potential, the current density decreases and changes its sign at the corrosion potential (Ecorr). The anodic response exhibits a well-defined anodic peak followed by a passive region. A noticeable increase in the anodic current density was observed after reaching the breakdown potential (Eb). The second anodic peak which may be attributed to onset of oxygen evolution was also observed. Moreover, the cyclic voltammograms revealed that hysteresis loop is absent for all the studied concentrations, indicating that AISI 202 SS in citric acid is highly resistant to pitting corrosion as also supported by the results of SEM. It was found out that the critical current density (icrit) increases with increasing citric acid concentration.