Application of extreme value analysis to crevice corrosion

Abstract Extreme value statistics have been applied to the crevice corrosion front that advances under elastomeric seals to aluminum surfaces. The exponential cumulative extreme value distribution provided an accurate description of the distribution of corrosion fronts quantified by tracing. Extreme value analysis can be applied to seals of small test samples to estimate the most probable maximum corroded depths of larger structures and, thereby, required seal widths. Variations in the calculated most probable maximum corroded depths introduced by subjectivity in tracing are considered. Crevice corrosion kinetics were determined using sets of fixtures salt spray tested for 2–60 days. These fixtures were assembled with 2024-T3 or 380 cast aluminum and silicone adhesive, ethylene–propylene–diene monomer, or Viton rubber elastomeric sealants. An empirical power law function was used to model the most probable maximum corroded depth under the seals versus test time. For tight seals to smooth surfaces, the dependence on time varied as t p with p =0.35–0.40, which is similar to the time dependence obtained in pitting corrosion studies.