Lim and PPG Industries Colleagues Probe Protection Mechanisms of Zinc-rich Primers

Mary Lyn Lim and colleagues at PPG Industries earned the President’s Lecture Series Award at Coatings+ 2021 for their research in coatings for steel used in bridges and other infrastructure for marine environments. The president of the Society for Protective Coatings selected the team’s paper, Efficiency of Zinc Content in Sacrificial Protection of Coatings, as the most favorable paper delivered during a technical session.

Lim earned her Ph.D. in materials science and engineering in 2016 working with John R. Scully, Charles Henderson Professor of materials science and engineering and department chair, and Robert G. Kelly, AT&T Professor of Engineering and professor of materials science and engineering. Scully and Kelly co-direct the Center for Electrochemical Science and Engineering within the UVA School of Engineering and Applied Science.

After graduation, Lim joined PPG Industries, a global supplier of paints, coatings and specialty materials based in Pittsburgh, as a corrosion subject matter expert.

“PPG gave me an opportunity to pioneer its corrosion research and to establish electrochemical capabilities that can aid in understanding product performance and accelerating product development,” Lim said.

Industry standards specify a minimum zinc content or concentration in zinc-rich primer, which is a well-established protection system for steel. The minimum standard places constraints on innovation, specifically around the introduction of more lightweight and cost-effective materials.

These challenges motivated the team to develop a technique to evaluate the properties and to probe the protection mechanisms of zinc-rich primers. The technique provides theoretical understanding complementary to environmental coating performance from standard corrosion cabinet tests. 

“In our study of coatings with a range of zinc loading, we found it is possible to achieve good protection when the zinc concentration is lower than the minimum stipulated,” Lim said. “Two protection systems are at play: the sacrificial protection provided by the zinc pigments and barrier protection from the paint itself.”

Lim developed simple experiments to measure anti-corrosion protection as a function of the paint formulation and the coating stack. These electrochemical techniques could be applied to other coating systems, with and without zinc. Further, the insights gained from the utility of these techniques will enable the development of novel coatings with lighter and cheaper pigments such as carbon.

The Association for Materials Protection and Performance incorporated the team’s test technique into an industry-wide, performance-based standard for zinc-rich primers in December 2021.

Lim recently took another step along her career path into a managerial role at Arconic Corporation, an aluminum rolled and extruded products company also based in Pittsburgh. Arconic has long-standing ties to the department as a destination point and proving ground for faculty and students.

Lim works with engineers, technologists and technicians to make aluminum less susceptible to corrosion while satisfying requirements for material strength. She conducted her dissertation research on 5000 series aluminum for naval applications, collaborating with several students working on a program funded by the Office of Naval Research.  

“I liked seeing the big picture and sharing an end goal with a large and diverse group of people,” Lim said. “Some group members were doing experiments, others were developing models or studying cracking behavior. We collaborated with colleagues outside the University and handed off our research to partners who are closer to the problem.” Their research helps increase ships’ service life and improves materials that will be used to build future generations of naval vessels.

“Mary Lyn was a great Ph.D. student,” Kelly said. “She quickly got her arms around a very technically challenging problem and made important scientific and engineering contributions to the field. She also collaborated extensively and successfully with other students, faculty, and industrial scientists. Her successes at PPG and now Arconic are no surprise, and we expect a lot more in the future."