CAREER: Resolving the origins of microgalvanic corrosion on metal surfaces

Non-Technical Summary

Corrosion (rust) is an age-old metallurgical problem whose underlying mechanisms are still not well-understood. The purpose of this research program is to uncover these hidden mechanisms and fully understand rust by using state-of-the-art instruments that allow us to see metals rust in liquids at the nanometer scale. By understanding the complex interplay between a material and its environment, transformative outcomes include an a priori approach for predicting and assessing corrosion, and a fundamental framework enabling engineers to design materials with superior corrosion resistance. Being able to control rust has far-reaching implications, from enabling ultra-light alloy design for aerospace applications, to materials for critical infrastructure, such as power generation, transportation, communications, defense, and water and waste treatment facilities. An integrated education plan extends the impact of this research by educating the next generation of corrosion engineers. Educational activities will benefit students from high school to graduate school, while providing opportunities for underserved and minority students to contribute to solving problems of national significance.

Technical Summary

Engineers design and process most engineering alloys to precipitate secondary phases; while these phases strengthen the alloy, they also act as the thermodynamic driving force for corrosion initiation. Inherent corrosion resistance can be tailored by selecting alloy constituents and processing routes to optimize fundamental electrochemical properties, but the appropriate constituents and processing routes are known only for select material systems and perform only under specific environmental conditions. How to expand beyond these systems to other materials and environments is still a tedious trial-and-error process. To address this limitation and advance the fundamental science needed to design for superior corrosion performance, this research connects the electrode potential of magnesium-lithium (Mg-Li) alloys in solution to their electronic structure by integrating state-of-the-art scanning Kelvin probe force microscopy (SKPFM) and scanning electrochemical microscopy (SECM) with first principles electronic property simulations. Using SKPFM to measure Volta potential (a surface electronic property) provides an experimental link spanning atomic structure and macroscale electrochemical properties via the work function. In complement, SECM quantifies the surface reaction kinetics during corrosion. Altogether, this research provides a new theoretical framework for relating local composition and structure to electrochemical properties--a critical factor governing material operational lifetimes.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.