Stress corrosion cracking mechanism of AISI 316LN stainless steel rebars in chloride contaminated concrete pore solution using the slow strain rate technique

Abstract

In this work, the stress corrosion cracking (SCC) mechanism of austenitic stainless steel AISI 316 LN rebar is studied along the entire stress-strain diagram by slow strain rate technique. The growth and passivity breakdown of the passive film is proved by non-destructive electrochemical tests as well as by current monitoring. The current density experiences multiple peaks related to the nucleation of metastable pits on AISI 316 LN surface near the yield stress (fy), followed by passivity breakdown of the passive film due to residual stresses, in addition to the chloride pitting process. The activation of dislocations dynamics induces high stress concentration in the passive film after reaching fy stress value, and consequently the development of high oxygen vacancies, increasing the oxygen diffusion, and therefore producing stable pits instead of metastable ones. The addition of 4 wt% Cl− in the concrete pore solution enhances the pitting process leading to film rupture, thus developing a mixed fracture mechanism characteristic of SCC.