Unified approach to localized and general corrosion of stainless steels

Localized and general corrosion of stainless steels is considered. In the case of localized corrosion, statistical parameters are deduced from the comparison of the distributions of breakdown and corrosion potential values to rank different materials, environments and designs. Cumulative frequency F is considered for breakdown (Eb) and corrosion (Ec) potential, and both are represented on a logarithm plot as E=E(log F). An extrapolated value of F (the risk H) corresponding to Eb=Ec is related to the field behavior of the material. The risk H is formally related to the corrosion current density (i ) of the general corrosion approach. An analogy between the formalism of the probabilistic treatment of localized corrosion of stainless steels and that of uniform corrosion is highlighted through Monte Carlo simulation. Introducing a discretization model of the general corrosion, the time evolution of the surface roughness during general corrosion of stainless steels is reproduced in agreement with the experimental results. According to this model, the general corrosion can be treated on a similar basis of the localized corrosion in terms of discretization of corroding areas, and vice-versa localized corrosion can be treated on a similar basis of the general corrosion in terms of statistical distributions of the potential values.