Modeling of Metastable Pitting: Towards a Better Understanding of the Effect of Alloying Elements

Modeling of pit chemistry in applied polarization mode is carried out using analytical calculations. The results lead to the formulation of critical conditions for pit stabilization. More detailed computing is performed to study pit stability behavior in terms of pit geometry and applied potential. The results fairly predict a transition pHT=f(log (σa.λ)) where λ = L2/r (L and r are respectively pit depth and mouth) is the geometrical factor, σa is the physical factor depending on the dissolution law. The consequences of these conditions are explored to throw light particularly on the role of alloying elements in pit stabilization. A key question as far as the durability of passive alloys is concerned.