Corrosion inhibition of AA7075: the quest to replace CR(VI)

AA7075 is used extensively in the aeronautical industry. Currently, corrosion protection of this alloy utilises Cr(VI) compounds, which are toxic and carcinogenic. The current study has focussed on characterising rare earth diphenyl phosphates as potential replacements for Cr(VI) as corrosion inhibitors for AA7075. Electrochemical and surface characterisation techniques, such as cyclic potentiodynamic polarisation, electrochemical impedance spectroscopy, scanning electron microscopy and x-ray photoelectron spectroscopy have been used to develop a model of the corrosion inhibition mechanism of these compounds occurring at the alloy surface. Visual inspection of alloy surfaces and analysis of the electrochemical and surface characterisation indicate these inhibitors are providing effective protection to AA7075 in corrosive environments.