Exploring corrosion protection of Mg via ionic liquid pretreatment

We present the development of a 10–100 nanometer thick surface film upon pure Mg on exposure to an ionic liquid (IL) based on the bis(trifluoromethanesulfonyl)amide (TFSA) anion. This film formation is the result of the oxidative reactivity of the metal in the IL, with the subsequent effect of ultimately protecting the underlying metal from corrosion in aqueous chloride containing solution. Film formation was studied in the IL using an electrochemical droplet cell. It was seen that this film is adherent and subsequently facilitates appreciable protection against corrosion as judged by subsequent electrochemical testing in the form of potentiodynamic polarization and impedance spectroscopy, along with direct observation. The physical film morphology was studied by electron microscopy and focused ion beam.