Fatigue corrosion cracking of an austenitic stainless steel using electrochemical noise technique

Purpose – To study the early stages of damage by corrosion fatigue (CF) in an austenitic stainless steel using the electrochemical noise (EN) Technique. Design/methodology/approach – Potential and current transients measured between two nominally identical electrodes during CF of an UNS S31603 SS were continuously monitored using a zeroresistanceammeter at different periods of exposure to seawater. The tests were carried out under cyclic loading of constant amplitude, stress ratio R=0 and load frequency of ω=0.17 Hz. The analysis was focused on both, crack nucleation sites and short fatigue crack growth, and the correlation between corrosionfatigue cracking and characteristics of potential transients and the associated intensity current. Findings – Measurements of EN, showed a good relationship between the potential transients and current fluctuations with the initiation and growth of intergranular corrosionfatigue cracks. The amplitude and frequency of potential transients and the intensity of current transients became more intense as the number of loading cycles increased. The initiation of crack events and small crack growth could be associated with the noise patterns with amplitudes of 20 and 70 mV and current density between 0.10 and 0.60 μA cm²; while large intergranular crack growth events, were due to coalescence of small cracks, and could be associated with patterns of 200 mV in amplitude and a cathodic current density of 8.0 μA cm². The crack nucleation sites generally were located at grain boundary triple points on the specimen surface. Originality/value – The EN Technique can be a good alternative to evaluate the early stages of damage by CF.