Date of Graduation

Spring 2018

Document Type

Honors Research Project

Degree Name

Bachelor of Science

Major

Corrosion Engineering

Research Sponsor

Dr. R. S. Lillard

First Reader

Dr. Hongo Cong

Second Reader

Dr. Rajeev Gupta

Abstract

In this work, COMSOL Multiphysics was used to model crevice corrosion of Nickel Alloy 625 in seawater. Initial model parameters included a bulk solution of 0.6M (Cl-) ASTM D1141-98 artificial seawater, a crevice length of 12.7mm, and applied current of 0.44VSHE. A crevice gap of 7μm and 10μm were compared using a 3.0m polarization curve of the simulated critical crevice solution for Alloy 625. A constant crevice gap of 10μm was used to compare varying polarization curves of 3.0m, 3.5m, and deaerated seawater. The model found a variation in free chloride concentration from the bulk to 1.29M (deaerated seawater polarization) and to 4.47M (3.5m polarization) at the tip of the crevice. Modeled data of species concentration, current density, and potential versus position in the crevice confirmed the effects of a smaller crevice gap and higher current density on the IR drop within the crevice. By lowering the potential from the passive region (0.44VSHE) to the active region on the polarization curve, crevice corrosion propagation was observed in the model.

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