Selfsimilar solutions for stress driven material dissolution: Advanced Fracture Mechanics for Life and Safety Assessments

During corrosive dissolution of metal ions from a body surface, an oxide compound is
produced. This compound forms a protective film that reduces the dissolution rate. When a
fraction of a millimetre depth is dissolved the dissolution rate become insignificant. However,
repeated loading will damage the film with continued dissolution as a result. In connection
with this a threshold strain is assumed to exist. This paper proposes a model where electrochemical processes and the mechanical load work together in forming a corrosion pit. The
ratio between the threshold strain and the remotely applied strain is shown to control the
shape of the pit. For small applied strains cracks are formed. A crack evolving from a surface
irregularity is studied. The growth rate of the crack is determined by the dissolution rate at
the crack tip. No crack growth criterion is needed. The growing crack is itself creating
conditions for strain concentration, which leads to a high crack growth rate. The model
simulates how dissolution forms a pit that grows to become a crack in a single continuous
process. For small loads the crack growth rate is independent of applied load.