Studies on pitting corrosion in austenitic stainless steel interfered by square‐wave alternating voltage with different parameters using multi‐potential steps method

摘要

>A multi‐potential steps (MPS) method was employed to simulate the square‐wave alternating voltage (AV) signals with different parameters. The electrochemical response and pitting propagation in a 316 austenitic stainless steel (SS) interfered by the simulated square‐wave AV in sodium chloride solution was investigated by means of electrochemical method, optical microscopy (OM), scanning electron microscopy (SEM), and atomic force microscopy (AFM) techniques. The results reveal that the square‐wave AV signal with amplitude of 800?mV and time step of 2?s triggers the formation of massive pits on 316 SS samples. The pit formation is suppressed with reducing the time step size of AV branches. Both the anodic and cathodic branches of AV contribute to the electrochemical response and pitting behavior on 316 SS samples. Decrease in the amplitude of cathodic branches of AV also suppresses the pit generation on sample surface. The ratio of anodic branch to cathodic branches of AV is discussed in this work. The width of fresh pits formed at different stages has a linear relation with the corresponding depth. The 316 SS exhibits honeycombed pits, which finally lead to an uneven corroded surface under square‐wave AV interference with large amplitudes.