Electrochemical Post-Processing of Zn-Ni Deposition on Steel Substrate for Reliable Composition; Impacts of Cd and Zn-Ni Coating Application

Smith, Leah, School of Engineering and Applied Science, University of Virginia
Jacques, Richard, EN-Engineering and Society, University of Virginia
Fitz-Gerald, James, EN-Mat Sci & Engr Dept, University of Virginia

In a push to replace toxic Cd coatings with the more sustainable Zn-Ni, there have been many delays due to technical concerns. My technical capstone research focuses on the mitigation of stress corrosion cracking with Zn-Ni through the development of a selective Zn dissolution process. My STS research is directly related to my technical research, focusing on the holistic impacts of switching from Cd to Zn-Ni.

My technical research aimed to mitigate stress corrosion cracking with Zn-Ni coatings on steel substrates by altering the potential of the coating to fall within the immunity region. The potential was tailored by altering the composition of the coating through a post-process, selective Zn dissolution method. This selective Zn dissolution method was pioneered and developed by the capstone team throughout this project. Results of experimentation were analyzed through scanning electron microscopy, energy-dispersive x-ray spectroscopy, and x-ray diffraction. Despite achieving the desired potential region, the samples used were largely stripped of their coating in the Zn dissolution process. As such, this method requires further refinement beyond the limitations of the capstone project.
In my STS research paper, I investigated the impacts of switching from Cd to Zn-Ni through human and environmental health, as well as geopolitics and economy. To bring clarity to what motivates and delays this particular push for sustainability, my research outlines how each element affects individuals and populations from cradle to grave. The defense industry has been granted exemptions from heavy Cd regulations until it finds a suitable replacement but progress has been slow. Despite Ni also being a carcinogen, Cd has a much longer half-life within the body and is known to easily leach into the environment, coming into contact with the vast majority of the general population. As critical minerals and key elements for the clean energy transition, Ni and Zn have increased supply risk compared to Cd, especially with the rise of resource nationalism and the uneven distribution of processing plants internationally. The effects and influences are addressed through an overarching ethical framework combining care ethics and utilitarianism.

Working on my STS and technical research in tandem was incredibly enlightening. The deeper understanding of the societal impacts gave me a greater sense of purpose and motivation in going about my technical research. Conversely, my technical research helped to remind me that there are more than social factors to consider. This balance between social and technical concerns is something that every engineer should review at length and with great care. Together, my STS and technical research explore that balance through Cd and Zn-Ni coatings.

I would like to thank my STS professor, Dr. Jacques, my team’s capstone advisors, Dr. Fitz-Gerald and Dr. Kelly, as well as our industry partners, Luna Labs and Rolls-Royce. In addition, I would like to acknowledge and thank my fellow capstone teammates, Emma Laubengayer, Morgan Small, Alex Uy, and Thomas Domer, for their hard work, support, and diligence.

BS (Bachelor of Science)
care ethics, Scanning Electron Microscopy, electrodeposition, Zn-Ni, Cadmium

School of Engineering and Applied Science
Bachelor of Science in Materials Science and Engineering
Technical Advisor: James Fitz-Gerald
STS Advisor: Richard Jacques
Technical Team Members: Emma Laubengayer, Morgan Small, Alex Uy, and Thomas Domer

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