Corrosion inhibition by metal ions delivered from amorphous alloys.

摘要

The overall technological goal of this research is to demonstrate the technical feasibility for a new, multifunctional, field replaceable, environmentally-friendly metallic coating system for aerospace applications. The dissertation specifically explored the possibility of active corrosion inhibition in a novel class of Al-Co-Ce(-Mo) alloys that can release Co2+, Ce3+ and MoO42- ions. Therefore, the scientific goals of this study were to characterize cerium, cobalt and molybdenum storage, release and inhibition of corrosion of a typical aerospace structural alloy (i.e., AA2024-T3) when delivered from bulk Al-Co-Ce and Al-Co-Ce-Mo alloys.; As a first step, the storage of the inhibitor species in the oxide layer formed on the alloy was characterized using surface sensitive tools, especially the valence states of the oxidized elements, in order to determine whether ions existing in the desired inhibiting forms and whether or not pH change of the local environment could trigger the release of inhibiting species desired given their valence state and pH dependent solubilities. The effect of the environmental triggers (pH, chloride ion concentration) on the scientific mechanisms and reaction order of ion release from the oxide films formed on the alloys was then characterized. The next step was to characterize the inhibitor functions and inhibition mechanisms of the individual ions when present in solutions as soluble species and to determine their critical concentrations required to suppress the corrosion of an aerospace aluminum alloy (AA2024-T3) in NaCl solution. The final step was to determine whether Al-Co-Ce(-Mo) metal coatings can deliver sufficient concentrations of such ions in small electrolyte volumes. This dissertation provides the first example of active corrosion inhibition via inhibitor release from a metallic coating and establishes a framework for studying the requirements of active corrosion protection as well as critical inhibitor concentrations.