Dissertation Proposal Defense – Gaoxiang Wu
Dr. Preet Singh, Advisor, MSE
Dr. Faisal Alamgir, MSE
Dr. Arun Gokhale, MSE
Dr. Matthew McDowell, MSE
Dr. Thomas Fuller, CHBE
"The Effect of Strain in Repassivation and Corrosion Behavior of Steels"
Metallic structures in the chemical process industry as well as in other structural applications show accelerated corrosion in areas with plastic deformation. During manufacturing, assembly and even service life, deformation is inevitably inflicted to the metals. Although much research has concentrated on the stress corrosion cracking (SCC) and corrosion fatigue, but the effect or role of strain on other types of corrosion in different alloy/environment systems is not very well understood.
The proposed study focuses on developing a fundamental understanding of the role of strain (elastic as well as plastic deformation) on active corrosion as well as repassivation behavior of metallic alloys, especially carbon steel and stainless steels. Activation controlled corrosion reactions are expected to be affected by the available strain energy especially in carbon steels where the materials are more likely to be in the active state. However, for stainless steels in which a stable passive film usually form on the surface, the strain energy may also be expected to influence the repassivation behavior and the characteristics of the resultant passive film. Therefore, localized corrosion, for example pitting, can also be affected by the strain. Another strain-related concern for corrosion in alloys arises by the presence of interstitial hydrogen in metals. The presence of hydrogen introduces additional strain into the metallic systems, meanwhile it also influences the surface chemistry of the alloys. As the mode and the extent of strain/deformation varies in different scenarios, the synergistic effects of strain energy, hydrogen transport kinetics, and altered surface chemistry can negatively affect the alloys’ corrosion resistance.
The proposed research can be categorized into four distinct branches: activation-controlled general corrosion, strain influenced passivation/repassivation, pitting corrosion, and influence of dissolved hydrogen on corrosion resistance of alloys. Results from this systematic study will provide much needed understanding of the role of strain on corrosion behavior of active as well as passive alloys in specific environments. This understanding will also be useful in modeling the anodic dissolution controlled SCC, where the similar effects are expected at the crack tip. This project would advance the knowledge of effect of strain on corrosion behaviors of steel systems, thereby preventing strain induced accelerated corrosion or failures in related areas.