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Computational Evaluation of Incomplete Coating Coverage

[+] Author Affiliations
Virginia G. DeGiorgi, Siddiq M. Qidwai

US Naval Research Laboratory, Washington, DC

Nithyanand Kota

Leidos Corporation, Reston, VA

Paper No. IMECE2014-37952, pp. V014T11A006; 8 pages
doi:10.1115/IMECE2014-37952
From:
  • ASME 2014 International Mechanical Engineering Congress and Exposition
  • Volume 14: Emerging Technologies; Engineering Management, Safety, Ethics, Society, and Education; Materials: Genetics to Structures
  • Montreal, Quebec, Canada, November 14–20, 2014
  • Conference Sponsors: ASME
  • ISBN: 978-0-7918-4963-7
  • Copyright © 2014 by ASME

abstract

Corrosion is a major cause of removal from service for many industries. Pitting, which involves localized corrosion of metals, can result in catastrophic failures because of resulting crack initiation and failure. The transition from pit to crack is influenced by the pit shape, which in turn is affected by the microstructure of the corroding material. In this work the authors investigate the importance of understanding the construction of a coating layer that may be present over the pit mouth. The coating layer may be by-products of another activity or a repair coating meant to prevent further damage. Stable pit growth occurs under diffusion control at rate that depends upon the extent of protective coating over the opening of the pit. The two extreme cases are: 1) no cover due to total loss of coating and 2) full cover over an existing pit. The cases in between would represent break in coating cover over an evolving pit. To investigate the effect of coating loss, a parametric study based on coating coverage percentage on the metal is investigated. The coating sample length and gap length are taken to be the same for all cases. Coverage percentages of 0% (no coating), 50%, 75% and 100% (fully coated) are analyzed for a set growth time. Severe numerical complications are discovered in the course of these analyses. The movement of the corrosion front parallel to the spatially fixed coating causes considerable mesh distortion that terminates the simulation prematurely requiring an impractically large number of re-meshing steps. The computational concepts investigated will be discussed in addition to evaluating the influence of pit coverage.

Copyright © 2014 by ASME

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