Comparison of Ceramic and Polymer Crevice Formers on the Crevice Corrosion Behavior of Ni-Cr-Mo Alloy C-22

摘要

The effect of the crevice former material on the evolution of localized corrosion-damage is determined in this study. A standard crevice corrosion test method is modified by the use of ceramic or polymer materials as the crevice former. Our overall focus is on the post initiation stage of crevice corrosion and to address factors that may limit the initiation of localized corrosion and also slow or stop the continued propagation of corrosion. Here the focus is on the measurement of damage evolution under controlled conditions. Crevice corrosion tests are performed under aggressive, accelerated conditions on Ni-Cr-Mo alloy C-22 and the less corrosion resistant 316 stainless steel (SS316). Under identical conditions in high temperature, concentrated chloride brines, the polytetrafluoroethylene (PTFE) Teflon tape covered ceramic is the most active crevice former on alloy C-22 while solid polymer crevice formers that are PTFE or polychlorotrifluoroethylene (PCTFE, Kel-F) are less active and ceramic crevice formers cause no crevice corrosion. The affects are important to the determination of the penetration rate and extent of corrosion damage by localized corrosion.