Screening-Level Life Cycle Assessment of Graphene-Poly(ether imide) Coatings Protecting Unalloyed Steel from Severe Atmospheric Corrosion

A major concern for exposed steel in structural applications is susceptibility to atmospheric corrosion. The International Organization for Standardization classifies atmospheric environments into six zones, C1-C5 and CX, based on factors such as humidity, airborne salinity, and acidic pollutants. The C5 and CX zones are characterized by aggressive atmospheric corrosivity that results in mass losses from steel structures. hot-dipped galvanized (HDG) zinc coatings are typically used to protect steel in C5 and CX environments. HDG coatings suffer from disadvantages related to shorter service lives and the need for frequent maintenance cycles. Graphene-reinforced poly(ether imide) (PEI) coatings have been proposed as suitable alternatives to address these issues. However, general concerns regarding the implications of nanomaterials make it necessary to understand the potential environmental impacts of these coatings. A screening-level cradle-to-grave life cycle assessment is conducted to evaluate the environmental performance of a graphene-PEI-steel structure when compared with a traditional HDG-zinc-steel structure. Impact assessment scores are calculated using the Tool for the Reduction and Assessment of Environmental and other Potential impacts v2.1 and SimaPro (v8.0.3). When considering inventory uncertainty, the graphene-PEI-steel structure yields smaller potential impacts in five of the ten categories assessed when assuming the graphene-based coating requires no maintenance during the service life of the structure. Scenario-based sensitivity studies reveal that the potential impacts are highly sensitive to the service life and maintenance needs of the coating, but insensitive to the use of thermally or chemically functionalized graphene to improve coating adhesion. Further research is needed to understand the long-term performance of the graphene-based coatings and reduce the uncertainty of the inventory.