Coating of Mild Steel by Aluminium in the Ionic Liquid [EMIm]Tf2N and its Corrosion Performance

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Abstract
The present paper shows for the first time that dense, adherent aluminium layers can be electrodeposited on mild steel in the water and air stable ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) amide [EMIm]Tf2N containing AlCl3 as a source of aluminium. The study was carried out using electrochemical techniques such as, cyclic voltammetry, chronopotentiometry, chronoamperometry, potentiodynamic polarization and electrochemical impedance spectroscopy, as well as surface analytical techniques such as SEM-EDX analysis and in situ STM. It was found that well adherent aluminium layers can be obtained after anodic oxidation of the substrate in the employed electrolyte prior to bulk deposition of aluminium. The corrosion behaviour of mild steel without and with coating by an aluminium layer with thickness of about 10 μm was investigated in 3.5% NaCl solutions. Compared to the uncoated sample, the Al-coated mild steel shows lower corrosion current and higher polarization resistance indicating the improvement of the corrosion resistance by Al coating.