Electrodeposition of Aluminium from Ionic Liquids

Cadmium plating has been used for many years in the aerospace industry for corrosion protection of high-strength steels. However, cadmium is toxic and carcinogenic. Due to health, safety and environmental protection, there is an urgent demand to replace cadmium for future aircraft production. 

Aluminium coatings electroplated from ionic liquids are considered as an alternative candidate to replace cadmium ones. The present studies are aimed at obtaining dense aluminium coatings adherent to the substrate with a definite thickness and mechanical properties. 

Low-temperature molten salts, or ionic liquids, which are a combination of organic cations and inorganic anions, are very attractive and promising media for the deposition of highly reactive metals that cannot be obtained from aqueous solutions. 

The first articles on the electrochemical deposition of aluminium from ionic liquids were published in 1980 by Robinson and Osteryoung [1] and by Welch and Osteryoung in 1981 [2]. Butyl-pyridinium chloride-AlCl3 was used as a medium for aluminium deposition with additives of benzene on different substrates, and the bulk deposition on brass (15 pk) was reported. 

Since that time many studies on A1 electrochemical deposition from ionic liquids were carried out in few directions [3-21] (i) deposition of A1 coatings, (ii) deposition of A1 alloys, (iii) investigation of the basic properties of ionic liquids with Al(III) salts, (iv) investigation of the mechanism of electrodeposition of Al(III) from ionic liquids and (v) characterisation of A1 deposits and optimisation of the deposition parameters for 

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Jiang T, Chollier MJ, Brym B (2006) Electrodeposition of aluminium from ionic liquids part 11 - studies on the electrodeposition of aluminum from aluminum chloride (Ald ) trimeth-ylphenylammonium chloride (TMPAC) ionic liquids. Surf Coat Technol 201 10-18... 

Jiang, T., Chollier Brym, M.J., Dube, G. et al. (2006) Electrodeposition of aluminium from ionic liquids part I - electrodeposition and surface morphology of aluminium from aluminium chloride (AlCljl-l-ethyl-S-methylimidazolium chloride ([EMImJCl) ionic liquids. Surf. Coat. Technol, 201(1/2), 1-9. 

Gao LX, Wang LN, Qi T et al (2008) Electrodeposition of aluminium from AlCyEtjNHQ ionic liquids. Acta Phys Chim Sin 24 939-944... 

Zheng Y, Zhang S, Lii X, Wang Q, Zuo Y, Liu L (2012) Low-temperature electrodeposition of aluminium from lewis acidic l-allyl-3-methylimidazolium chloroaluminate ionic liquids. Chin J Chem Eng 20(1) 130-139. doi 10.1016/S1004-9541(12)60372-3... 

Abbott, A.P., Eardley, C.A., Farley, N.R.S. et al. (2001) Electrodeposition of aluminium and aluminium/platinum alloys from AlClj/benzyltrimethylammonium chloride room temperature ionic liquids. J. Appl. Electrochem, 31(12), 1345-1350. 

Although many ionic liquids and deep eutectic mixtures based on choline have the advantages to be cheap and no-toxic, they are all hydrophilic and miscible with aqueous solvents. This may be a problem for applications such as the extraction of metal ions from an aqueous phase or the electrodeposition of reactive metals (aluminium, magnesium, tantalum..). 

The electrodeposition of a thin aluminium layer was performed from a chloroalumrnate ionic liquid (AlCl3/[C4mim][Cl] molar ratio 2/ 1) on Al- Li P90 alloy [45]. A crucial aspect was the superficial treatment applied before the aluminium deposition, performing mechanical polishing inside a globe box where... 

Bakkar A, Neubert V (2013) Electrodeposition and corrosion characterisation of micro- and nano-crystalline aluminium from AlC13/l-ethyl-3-methylimidazoliinn chloride ionic liquid. Electrochim Acta 103 211-218. doi 10.1016/j.electacta.2013.03.198... 

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