Comprehending the role of individual microstructural features on electrochemical response and passive film behaviour in type 304 austenitic stainless steel

The individual implication of sensitization, grain size, residual strain, and grain boundary character distribution on semiconducting response of passive film in 304 stainless steel is investigated. Involvement of higher donor densities in the sensitized specimen deteriorated passive film stability. The greater density of random grain boundaries in fine-grained specimen promoted the defects formation in the passive film. In contrast, higher fraction of ‘special’ boundaries and triple junctions, realized through grain boundary engineering, suppressed the formation of defects in the passive film. Interestingly, defects induced via straining accelerated the oxygen vacancy formation at metal/film-interface, which depreciated the protectiveness of passive film.