Ability of acoustic emission technique for detection and monitoring of crevice corrosion on 304L austenitic stainless steel

This experimental work was aimed at investigating the ability of acoustic emission (AE) technique for detection and monitoring of crevice corrosion on 304L austenitic stainless steel. Crevice initiation, propagation and repassivation was controlled by additions of hydrogen peroxide and hydrochloric acid and by the extent of the applied torque of crevice assembly, in the presence of chloride ions. The simultaneous measurements of corrosion potential of the specimen and AE global activity during the test, as well as the characterization of acoustic parameters of AE signals, evidences a good correlation between potential and AE activity fluctuations, AE rate and amplitude of crevice damage in terms of weight loss and metallic surface affected, in each tested experimental condition. Moreover, the evolution of cumulative% of AE signals number versus selected acoustic parameters shows that rise time, counts number, duration and cumulative energy of AE signals are affected by crevice development. Finally, visualization of crevice initiation and propagation during the test allows to propose that bubbles formation from cathodic reactions within the crevice is the emissive mechanism.