Anodic dissolution model rupture

Fig. 13.23 Schematic of crack penetration with time in the film-rupture/anodic-dissolution model [29]...

Logan [42] suggested a film rupture or sHp-step dissolution model for SCC mechanism where the crack is initiated by locahzed anodic dissolution. This mechanism postulates that plastic strain in the metal at the crack tip causes a fracture of the oxide barrier film. The film rupture model (FRM) assumes a repetitive, cycling process of film rupture, dissolution of the underlying metal, and repassivation. 

Mechanisms of SCC. Over the years, a variety of mechanisms or models have been proposed to explain SCC phenomena in titanium alloys (Ref 80). In general, SCC is the anodic dissolution in highly localized areas that, aided by an applied tensile stress, propagates cracks into the metal. Crack advance occurs by discontinuous rupture of the oxide film at the crack tip. 

Figure 4.45 Schematic of film rupture model (a) illustrates the main feature of the model—the protective film is ruptured at the crack tip by localized slip, permitting propagation by anodic dissolution. The crack tip is depicted in greater details in (b) which illustrates the view that crack advance results from a number of independent film rupture and transient dissolution events. (From Staehle, R.W. (1979). Stress Corrosion Cracking in Alloys, NATO, p. 223)...

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