  We present a new theoretical and numerical framework for modelling
mechanically-assisted corrosion in elastic-plastic solids. Both pitting and
stress corrosion cracking (SCC) can be captured, as well as the pit-to-crack
transition. Localised corrosion is assumed to be dissolution-driven and a
formulation grounded upon the film rupture-dissolution-repassivation mechanism
is presented to incorporate the influence of film passivation. The model
incorporates, for the first time, the role of mechanical straining as the
electrochemical driving force, accelerating corrosion kinetics. The
computational complexities associated with tracking the evolving
metal-electrolyte interface are resolved by making use of a phase field
paradigm, enabling an accurate approximation of complex SCC morphologies. The
coupled electro-chemo-mechanical formulation is numerically implemented using
the finite element method and an implicit time integration scheme;
displacements, phase field order parameter and concentration are the primary
variables. Five case studies of particular interest are addressed to showcase
the predictive capabilities of the model, revealing an excellent agreement with
analytical solutions and experimental measurements. By modelling these
paradigmatic 2D and 3D boundary value problems we show that our formulation can
capture: (i) the transition from activation-controlled corrosion to
diffusion-controlled corrosion, (ii) the sensitivity of interface kinetics to
mechanical stresses and strains, (iii) the role of film passivation in reducing
corrosion rates, and (iv) the dependence of the stability of the passive film
to local strain rates. The influence of these factors in driving the shape
change of SCC defects, including the pit-to-crack transition, is a natural
outcome of the model, laying the foundations for a mechanistic assessment of
engineering materials and structures.
