Finding a Replacement for Hexavalent Chromium Sacrificial Paint; The Struggle over Public Policy Responses to Hexavalent Chromium in the United States

Under its Registration, Evaluation, Authorization, and Restriction of Chemicals (REACH) regulation, the European Union has banned hexavalent chromium compounds, which are carcinogenic. Both to comply with this regulation and to protect public health, manufacturers urgently need a suitable alternative. Hexavalent chromium coatings prevent corrosion through its self-healing capabilities.

Students at the University of Virginia were tasked to develop an alternative coating system that protects the steel components inside Rolls Royce’s aerospace engine. The hexavalent chromium compounds inside the original coating protected the steel from corrosion damage but also contributed to protection at high temperatures. Due to the nature of the corrosion protection mechanism utilized by hexavalent chromium, only certain materials could be considered as substitutes. Zinc behaves like hexavalent chromium but lacks its high temperature exposure capabilities. A coating system relying on a zinc-based coating from Sherwin Williams acts as the main corrosion protection, while topcoats of high temperature sol-gel coatings were applied to act as thermal barriers. A test environment of thermal exposure before salt-fog exposure was developed to screen different high temperature sol-gel coatings that covered the Sherwin Williams base layer.

Since the US Environmental Protection Agency introduced more rigorous standards, researchers have proposed Zinc and other materials as alternatives to hexavalent chromium. Though regulated, hexavalent chromium is still in widespread use in the United States, despite its carcinogenic effects. To resist efforts to ban hexavalent chromium, industry has engaged in a power struggle with public health proponents and environmentalists since the 1970s. Other failings in establishing policy on carcinogens can also be attributed to these three obstacles. Industry presents evidence that standards are not capable due to the technology available and limited support from government. In this effort, industry has engaged in lobbying and manipulation of science.

School of Engineering and Applied Science

Bachelor of Science in Materials Science and Engineering

Technical Advisor: James Fitz-Gerald

STS Advisor: Peter Norton

Technical Team Members: Marcus Dupart, Jesper Braley