Abstract
One important factor affecting crevice corrosion of passive metals is the crevice geometry, e.g. the gap and shape of the crevice. Depending upon the materials properties, different crevice formers can affect the crevice geometry, e.g. a polymeric crevice former can conform to the surface roughness of a metal specimen. The objectives of this work are to investigate the crevice corrosion damage propagation of alloy 22 (N06022) with different crevice former materials and to address factors that may limit the initiation of localized corrosion and also factors that may slow or stop the continued propagation of corrosion.
Crevice formers made from ceramic, polymer, polytetrafluoroethylene (PTFE) tape covered ceramic and alloy 22 are compared in controlled crevice corrosion tests under highly aggressive, accelerated conditions. Cyclic potentiodynamic polarization and potentiostatic polarization methods are used to determine the crevice corrosion behavior of alloy 22 in high temperature, concentrated chloride brines. Results show that crevice corrosion of alloy 22 is affected by the crevice former materials and by the surface finishes of the crevice former and specimen. It is found that crevice corrosion initiates near the edge and under the crevice former and propagates further into the crevice. The corroded alloy can become re-passivated after undergoing an amount of corrosion. The results provide insight into the localized corrosion process and mechanism of alloy 22 in high temperature brines.
