Unravelling the corrosion inhibition mechanisms of bi-functional inhibitors by EIS and SEM–EDS

In this work the corrosion inhibition effect of aluminium alloy AA2024-T3 in aqueous solution by an inorganic cerium salt (i.e. cerium chloride) and an organic one (i.e. cerium dibutyl phosphate) is presented. The research involved long term immersion tests (up to 8 d) followed up by EIS. The analysis was complemented by a systematic selection of the most probable equivalent circuits and scanning electron microscope analysis combined with X-ray energy dispersive spectroscopy. This study highlights the different corrosion protection mechanisms of organic and inorganic ions. A model of protection is suggested based on the combination of techniques.

► Differences in protection mechanism by inorganic and organic–inorganic inhibitors is investigated by the combination of EIS and SEM–EDS.
► The selection of most probable equivalent circuits to fit EIS is performed in a systematic manner.
► A model for the protection of AA2024 by Ce and organophosphate corrosion inhibitors is proposed.