TY: THES T1 - Corrosion and corrosion inhibition in multi-material combinations A1 - Ofoegbu, Stanley Udochukwu N2 - Modern high-strength but environmentally friendly, fuel-efficient and weight-optimized designs vital to the aeronautical and transport industries have resulted in the multi-material concept in which a wide range of materials are employed to exploit the various desirable mechanical and physical properties. These multi-material design concepts are susceptible to corrosion as the chemical and electrochemical properties of their constituent materials can vary widely. Since current corrosion mitigation strategies are not focused on these multi-material systems, there is an urgent need to understand the mechanism of the corrosion processes operative in these multi-material assemblies and develop suitable multi-material corrosion mitigation solutions in tandem with the increasing design trend towards multi-material structures. This work has focused on understanding the mechanism of multi-material corrosion in two multi-material systems that are of relevance to the aeronautical and transport industries; Al - Cu - CFRP (carbon fiber reinforced polymers) and Zn - Fe - CFRP galvanic systems respectively. On the basis of the insights obtained, appropriate multi-material corrosion mitigation options using inhibitors are to be identified and verified at the laboratory scale. The thesis objectives have been pursued by an incremental escalation technique in which the five individual materials constituting the two multi-material galvanic systems were first studied at the macro-scale in quiescent 50 mM NaCl solutions with and without inhibitors. Particularly, CFRP the only non-metallic material used was extensively studied with a view to understanding its deleterious electrochemical action as an efficient cathode when coupled to metals and how to mitigate it. Next technologically relevant dual material couples most relevant to the two galvanic systems were studied at the macro- and micro-scales, on the premise that inhibitors efficient at mitigating galvanic corrosion in these simpler components (Al - CFRP, Al - Cu, and Cu - CFRP for the Al - Cu - CFRP galvanic system) and (Fe - CFRP, Zn - CFRP, and Zn - Fe for the Zn - Fe - CFRP galvanic system) are prone to be effective for an entire multi-material system. Finally, promising inhibitors identified from dual material galvanic studies are tested on the multi-material combinations leading to identification of efficient multi-material corrosion inhibitors for both the Al - Cu - CFRP and Zn - Fe - CFRP multi-material combinations. The results demonstrate better understanding of the electrochemical behaviour of CFRP under cathodic polarization on galvanic coupling with metals and potential strategies to suppressing its ability to support cathodic reactions, and successful identification of potential inhibitors for mitigating multi-material corrosion in both systems. On the basis of results obtained in this work a scheme for monitoring degradation of CFRP was postulated as well as plausible mechanism(s) of multi-material corrosion and multi-material corrosion inhibition in Al - Cu - CFRP and Zn - Fe - CFRP multi-material galvanic systems, respectively UR - https://ria.ua.pt/handle/10773/24097 Y1 - 2018 PB - No publisher defined