Critical Characteristic Dimension or Geometry for Determining the Susceptibility of a Crevice to Crevice Corrosion Available to Purchase

Crevices are invariably present in engineering structures. Hence, it is of interest to develop the ability to predict which geometries will, or will not, lead to crevice corrosion. Since many crevice corrosion theories have been proposed that depend on the material-environment combination, two systems have been selected for study: mild steel (MS) under anodic polarization in a sodium acetate–acetic acid buffer solution (NaAc-AcH) and Al in a sodium chloride (NaCl) solution. The onset of crevice corrosion is respectively believed to be determined by a critical potential drop (IR drop theory for MS in NaAc-AcH) and a critical species’ concentration (critical crevice composition theory for Al in NaCl). In both cases, these critical values can be translated, by computation, into a critical characteristic crevice dimension determining the onset of crevice corrosion in one-dimensional crevices. The critical characteristic dimension marks the limit between crevices that show or do not show crevice corrosion. The calculations for the system where the critical crevice composition theory is operative have been performed with a finite element code to describe the mass transport of the various species involved. This approach allows the criterion (critical potential drop or critical crevice composition) to be evaluated for crevices of any geometry in real components.