Materials Science and Engineering Location: Zoom
Add to Calendar 2021-07-22T08:30:00 2021-07-22T11:00:00 America/New_York Ph.D. Dissertation Defense: Ryan M. Katona Title:    Anodic and Cathodic Limitations on Localized Corrosion and Stress Corrosion Cracking Propagation of Stainless Steel 304L in Atmospheric Environments Zoom

Title:    Anodic and Cathodic Limitations on Localized Corrosion and Stress Corrosion Cracking Propagation of Stainless Steel 304L in Atmospheric Environments

Abstract:    The formation of localized corrosion, characterized by the highly focused metallic dissolution, is likely in marine environments. The highly focused anodic dissolution is characterized as an autocatalytic process and requires the presence of a minimum concentration of metal chlorides that undergo hydrolysis destroying localized passivity. If these conditions are not met, repassivation will commence and corrosion will stifle.  Additionally, the anodic processes must be supported by a cathodic reduction reaction on the external environment. In atmospheric scenarios, a finite water layer thickness combined with solution properties can provide significant ohmic drop in solution which in turn creates a finite cathode.  At some point, localized corrosion features grow to a size that requires a cathode current that cannot be obtained by the surrounding material creating a maximum pit size. Both anodic and cathodic processes are influenced by solution concentration, solution composition, and temperature and will influence the extent of corrosion on the surface of an alloy. Finally, solution properties are dictated by the exposure relative humidity. As the relative humidity changes both diurnally and seasonally, a wide range of solutions are possible in marine environments. This dissertation addresses environmental changes (relative humidity and temperature) on anodic and cathodic processes. These properties are combined in order to inform upon localized corrosion through analytical and Finite Element Modeling.

 

The main goals of this dissertation are to (i) develop a robust understanding of reaction mechanisms as a function of environmental parameters, (ii) utilize and enhance analytical predictive capabilities to understand governing factors and more accurately predict pitting corrosion damage, and (iii) utilize FEM modeling approach, electrochemical techniques, and pertinent instrumental characterization tools to systematically investigate the effect of electrolyte layer thickness, solution chemistry, materials surface properties, and geometry on localized corrosion and SCC damage distributions.

 

Overall, this dissertation developed a fundamental understanding of the effect of environmental parameters on localized, pitting corrosion and stress corrosion cracking. The work provides for a  complete means of predicting localized pitting corrosion of SS304L in marine environments as a function of relative humidity which can be used for diagnostic measures. Electrochemical characterization in this dissertation provides meaningful information for better understanding of corrosion processes and identifies governing factors (both experimental and modeling techniques) of corrosion processes.

Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. This document is SAND2021-8052 A.

All interested persons are invited to attend.

 

 Committee:

Dr. James Burns, Chair, UVA MSE

Dr.  Robert Kelly, Advisor, MSE

Dr.  Andres Clarens, CEE

Dr. John Scully, MSE

Dr.  Giovanni Zangari, MSE

Dr. Eric Schindelholz (Ohio State Univ., MSE)

Dr. Rebecca Schaller (Sandia National Laboratories)

Zoom:   

https://virginia.zoom.us/j/96984291965?pwd=U2JjMU5Hc1FlOU1nRUdVODljMU9JZz09

Meeting ID: 969 8429 1965

Passcode: 200040