Electrodeposition of Al-Mn-Zr ternary alloy films from the Lewis acidic aluminum chloride-1-ethyl-3-methylimidazolium chloride ionic liquid and their corrosion properties

Abstract

The electrodeposition of Al-Mn and Al-Mn-Zr alloy films on low carbon steel substrate from the Lewis acidic aluminum chloride-1-ethyl-3-methylimidazolium chloride (AlCl3/[Emim]Cl) ionic liquids with different metal salts is investigated. The addition of ZrCl4 in the bath with 0.04M MnCl2 induces the higher overpotential for the electrodeposition, which decreases the size of the electrodeposited primary crystallites. Rounded nodular particles composed of many primary nanocrystallites are obtained by the electrodeposition in the bath containing 0.04M MnCl2 and 5mM ZrCl4. The close packing of these nodular particles results in the formation of the Al-Mn-Zr ternary alloy film with a dense structure. Compared with the bare carbon steel electrode, the as-electrodeposited Al-Mn and Al-Mn-Zr alloy film electrodes shows much more negative corrosion potentials, indicating their cathodic protection effect on the substrate. As the Zr content in the alloy films becomes larger, the corrosion current density first decreases, and then increases. The Al-Mn-Zr ternary alloy film with 1.871at.% Zr, which is prepared in the bath with 0.04M MnCl2 and 5mM ZrCl4, manifests the lowest corrosion current density. This can be attributed to its dense film structure and good combination with the substrate.