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Deformation-promoted nucleation of corrosion cracks: State, problems, and perspectives

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  • Stress Corrosion Cracking
  • Crack Geometry
  • Crack Incubation
  • Crack Evolution
  • Moving Boundary Problems
  • Finite Elements
  • Mathematics


One model for corrosion crack initiation and propagation in metals is reviewed. The model incorporates three physical processes operating at the metal-environment interface – material dissolution, passive film formation and surface straining. The dissolution triggers surface advance; the passivation restrains the access of the environment to bare metal; the deformation causes for passivity breakdown. An essential advantage of the model is that it allows for formulating the crack development as a mechanical moving boundary problem, without the need for a specific crack growth criterion. The problem is solved using a finite elements and a moving boundary tracking procedure. The simulations demonstrate how cracks form and grow in a single continuous course. Key results for plane cracks nucleating from surface pits in an elastic-plastic material body under low-cycle fatigue load are presented. The developed cracks morphology is found independent of the initial pit size. Plasticity is found to influence the curvature at the tip of the nucleated corrosion cracks, but not its width. Mathematical and finite element analyses of stationary cracks with appropriate geometry are involved to explain the behaviour predicted by the model. The most important evolution length parameter, the width of the corrosion crack, is found to depend on the size constraints of the tracking procedure. This limits the validity of the model to the crack nucleation stage. It is concluded that the model is deficient for determining all length scales of a developed crack observed in reality. Physical processes to be considered in an advanced model are proposed and discussed.

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