Experiments in the Oxidation of Super Alloys Explain Corrosion Resistance

Petra Reinke, professor of materials science and engineering at the University of Virginia, deconstructs how metal surfaces protect themselves from corrosion. Her research focuses on oxidation, a chemical reaction that occurs naturally when oxygen reacts with the surface of metals or alloys.

“This oxide layer protects the alloy, much like a coat worn in bad weather as protection against the elements.” Reinke said.

Reinke’s research helps us understand the oxidation of nichrome and related super alloys down to the atomic scale. Just a small percentage of chromium added to nickel greatly improves corrosion resistance. The oxide layer formed with these two elements is more uniform and tightly bonded with the surface metal.

Because of their excellent mechanical properties and a high degree of corrosion resistance, these alloys find practical application in an array of industrial and military systems. A deeper understanding the oxidation process will ultimately lead to a wider variety of corrosion-resistant metals.

Reinke recently earned funding from the National Science Foundation to conduct experiments to unravel the detailed mechanisms of the oxidation process. This is especially interesting in the presence of a third element, tungsten or molybdenum, which further improves the protective function of the oxide layer.

“These elements’ anti-corrosive properties are well known, but knowledge gaps remain, especially in our fundamental understanding of the very first reaction steps when the alloy surface is transformed to an oxide,” Reinke said. Whereas a typical approach would look at how metals break down, and the composition and structure of a thick oxide, Reinke wants to start with a really clean metal to explain how oxidation begins.

“Are there things we can do to help jump-start the process and ensure a stable protective oxide layer? Which chemical mechanisms can we replicate to improve corrosion resistance under challenging conditions such as seawater? These are the questions we expect to answer through these new experiments,” Reinke said.

Reinke looks forward to involving her graduate students in this work and introducing surface science to a diverse group of learners. The National Science Foundation grant supports a joint effort with Ashleigh Baber, assistant professor of materials chemistry at James Madison University.

“Ashleigh and I look forward to introducing students to this exciting field of research,” Reinke said. Reinke and Baber will build an online class in surface science, fulfilling a need for graduate and advanced undergraduate students at both institutions. This effort is particularly timely in view of the challenges that come with the COVID-19 crisis and increased demand for high-quality online education.