1 April 2003, University of Maryland, College Park, MD
Title of Lecture: Seawater Crevice Corrosion of Nickel Superalloys
Speaker: Dr. Farrel Martin, GEO-Centers, Inc., Naval Research Lab's Center for Corrosion Science and Engineering
Crevice corrosion susceptibility is a function of many parameters. The interrelationship between each of these parameters has yet to be fully quantified, let alone completely understood. The present work attempts to explain the interrelationship between some of these parameters for Alloy 625 and similar nickel superalloys during exposure to natural seawater. For example, electrochemical potential of the boldly exposed surface strongly affects initiation and propagation of crevices, while seawater temperature and tightness of the crevice exert a significant influence on the potential required for initiation. In addition to affecting the crevice initiation and repassivation potentials, seawater temperature influences the corrosion potential obtainable due to environmental factors in natural seawater. This is important since ennoblement of the corrosion potential in natural seawater is tied to crevice initiation. An unexpected finding was that gasket materials affect the crevice susceptibility, and there are significant differences in crevice susceptibility for seemingly identical gaskets. This effect was tied to the observation that some gaskets (which do not intentionally contain inhibitors) exude a crevice-inhibitive film. And, in the spirit of April 1st, a surprising find at the "head" of a crevice!
Seventeen attendees were present for the talk (including the speaker). In addition, 3 students from the University of Virginia presented posters; Meghan Goldman, Ashley Lucente and Francisco Presuel.