Aluminium electrodeposition

Suchentrunk, R., Corrosion Protection by Electrodeposited Aluminium , Z. Werkstofftechnik, 12, 190-206(1981)... 

The early history of ionic liquid research was dominated by their application as electrochemical solvents. One of the first recognized uses of ionic liquids was as a solvent system for the room-temperature electrodeposition of aluminium [1]. In addition, much of the initial development of ionic liquids was focused on their use as electrolytes for battery and capacitor applications. Electrochemical studies in the ionic liquids have until recently been dominated by work in the room-temperature haloaluminate molten salts. This work has been extensively reviewed [2-9]. Development of non-haloaluminate ionic liquids over the past ten years has resulted in an explosion of research in these systems. However, recent reviews have provided only a cursory look at the application of these new ionic liquids as electrochemical solvents [10, 11]. 

Aluminium may be applied as coatings by metal spraying, cladding, hot-dipping and electrodeposition, though the last-named process is difficult to apply and by far the largest proportion of aluminium-coated metals are produced by the first two methods. 

Couch, D. E. and Connor, J. H., Nickel-Aluminium Alloy Coatings Produced by Electrodeposition and Diffusion , J. Electrochem. Soc., 107, 272 (1960)... 

Holland, B. O., Aluminium Coating of Steel with Special Reference to Electrodeposition , Broken Hill Ply, Technical Bulletin, 3 No. 1, 29 (1959)... 

Articles of steel, copper or brass which require a thicker coating than is possible by chemical replacement, and which are difficult to tin by normal electrodeposition, may be coated by immersion in alkaline sodium stannate solution in contact with aluminium suitably placed to act as anode. 

Bellows Nickel bellows can be made by electrodeposition onto a grooved cylinder. In this case, the nickel coating cannot be slid off, and so the substrate must be removed destructively. The grooved cylinders or mandrels are frequently of aluminium alloy which is dissolved away in caustic alkali when the nickel deposition is completed. Uses include pressure switches, flexible couplings, and pressure transducers . 

It consists in a deposition of ions from an electrolyte onto the cathode in an electrolytic cell, under the influence of an applied potential. Usually the process is accompanied by material dissolution from the anode. The electrowinning from aqueous solutions is an important commercial method for the production (and/or refinement) of many metals, including, for instance, chromium, nickel, copper, zinc. As for the electrodeposition from non-aqueous solutions, the primary production of aluminium, electrodeposited from a solution of A1203 in molten cryolite, is a typical example. Other metals which may be regularly reduced in a similar way are Li, Na, K, Mg, Ca, Nb, Ta, etc. 

A Raney nickel surface is also suitable for electrocatalytic hydrogenation [205]. This surface is prepared by electrodepositing nickel from a solution containing suspended Raney nickel alloy (Ni 50% A1 50%). Some alloy particles stick to the surface, which is then activated by leaching the aluminium using hot aqueous sodium hydroxide. Cyclohexanone, acetophenone and benzil have been converted to the corresponding alcohol and there is no stereoselectivity for the formation of hydrobenzoin from benzil. 

Hurley, EH. and Wier, T.P, The electrodeposition of aluminium from nonaque-ous solutions at room temperature. /. Electrochem. Soc., 98,207-212,1951. 

Today, a large number of important technologies are based on or related to electrodes reactions. Besides the chlor-alkali and aluminium industries, energy conversion in batteries and fuel cells, electrodeposition, electrorefining, organic electrosynthesis, industrial and biomedical sensors, corrosion and corrosion protection, etc. are amogst those technologies. In many of them, kinetic, catalytic or specificity aspects of electrode processes are of enormous importance. 

Zein El Abedin, S., Moustafa, E., Natter, H., Hempelmann, R., and Endres, F. (2005) Additive free electrodeposition of nanocrystalline aluminium in a water and air stable ionic liquid. Electrochem. Commun., 7,1116. 

Figure 12.8 shows the photo of a deposited aluminum layer obtained potentio-statically on a mild steel substrate at -0.3 V (vs. Al) for 4h in the upper phase of the mixture [EMIM] TFSA/6 M AICI3. The substrate was electrochomically etched at 1V (vs. Al) for 2 min prior to electrodeposition. The aluminium layer adheres so well that it can be mechanically polished to a mirror appearance. 

Raney Ni particles become entrapped in the electrodeposited Ni under the influence of a cathodic current and stirring. The electrocatalytic behavior of this material was characterized by the Tafel parameters for H2 evolution for various quantities (mg cm" ) of the Raney particles deposited. Particle size and aging effects were also determined. Kinetic parameters for the HER on various coatings were determined and compared (181). A related process for binding and cementing electrocatalytic Ni powders used a three-dimensional aluminium phosphate polymer (182). The Ni active material developed in the form of spiky filaments. 

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..). 

Zhao Y, Vandemoot TJ (1997) Electrodeposition of aluminium from room temperature AICI3-TMPAC molten salts. Electrochim Acta 42 3-8... 

Endres F, Schweizer A (2000) The electrodeposition of copper on Au(lll) and on HOPG from the 66/34 mol% aluminium chloride/l-butyl-3-methylimidazolium chloride room temperature molten salt an EC-STM study. Phys Chem Chem Phys 2 5455-5460... 

Endres F, Freyland W (1998) Electrochemical scanning tunneling microscopy investigation of HOPG and silver electrodeposition on HOPG from the acid room temperature molten salt aluminium chloride - l-methyl-3-butylimidazolium chloride. J Phys Chem B 102 10229-10236... 

Zein El Abedin S, Endres F (2006) Electrodeposition of nano- and microcrystalline aluminium in some water and air stable ionic liquid. Chem Phys Chem 7 58-65... 

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... 

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

---