The effect of electrochemically induced annealing on the pitting resistance of metastable austenite stainless steel

Deformation-induced martensites in metastable austenite stainless steels affect their physical and chemical properties. Electrochemically induced annealing (EIA) is a recently discovered phenomenon. Although the reason why EIA treatment causes martensite to decrease or disappear is not clear, the effect of the martensite decrease or disappearance is supposed to be the same as that caused by heat-treatment annealing. The pitting resistance of the EIA-treated samples is compared with that of the untreated ones, through open-circuit potential, metallurgical microscope observation, and potentiodynamic scanning. The following results are obtained for the EIA-treated samples, after a 1.5-V anode charge in a 3.5 pct NaCl solution, as compared with the untreated samples: the deepest pit in the treated samples is far more shallow than the deepest pit in the untreated samples; there is far less pitting in the treated samples than in the untreated samples; and the largest pit in the treated samples is much smaller than the largest pit in the untreated samples. Initially, the open-circuit potential of the EIA-treated sample was 64 mV higher than that of the untreated one, but they reach close values after certain period of time. The pitting breakthrough potential, E-b, of the EIA-treated sample is about 0.2 V higher than that of the untreated one. Therefore, EIA is a method that has the potential to promote. the pitting resistance of metastable austenite stainless steels.