Magnesium electrochemical deposition

Although the electrochemical deposition of magnesium from Grignard reagents is not interesting for organic chemists, yet the investigations into such processes undertaken... 

Recently, Sharma [299], at General Motors, proposed a low cost method for the production of Al-Mg alloys, which can be used in the automobile industry and for desulfurization of steel. The unit cell is shown in Figure 29. The cathode of liquid aluminum is at the bottom of the cell where magnesium is deposited. The electrolyte is a mixture of molten chlorides in which partly dehydrated MgCl2 is dissolved and the electrolysis temperature is 750°C. The same author also described another method to produce magnesium metal using an electrochemical cell with bipolar electrodes, shown in Figure 30. 

The electrochemical deposition of magnesium was investigated in the ionic liquids [Emim]BF, 1-butyl-1-methylpyrrolidiniumtriflate ([BMP]TfO) and 1-butyl-... 

Superconducting rotors for the experiments were made of either solid niobium or lead-plated sapphire, plastic, aluminum, or magnesium spheres. The spheres were plated either by electrochemical deposition or vacuum deposition. Tests have indicated that these methods can be refined to produce properties similar to the parent material. 

When considering the conventional polar aprotic families of solvents (mentioned in Figs 13.2 and 13.3), esters, alkyl carbonates, sulfones, amides and dimethylsulfoxide (DMSO), can be suspected as being reactive with active metals such as magnesium (see later discussion). Only ethers seem to be suitable for reversible Mg electrodes and electrochemical deposition of magnesium metal. 

On solutions with a wide electrochemical window (>2V) in which magnesium (Mg) deposition is reversible... 

Magnesium reacts very slowly with water at ordinary temperatures. Although the metal occupies a position higher than hydrogen in the electrochemical series, the reaction practically stops after a thin protective film of insoluble hydroxide deposits over the surface of the metal. The reaction is moderately fast in hot water and rapid in steam. The products are magnesium hydroxide and hydrogen ... 

Sacrificial anode — is a piece of metal used as an anode in electrochemical processes where it is intended to be dissolved during the process. In -+ corrosion protection it is a piece of a non-noble metal or metal alloy (e.g., magnesium, aluminum, zinc) attached to the metal to be protected. Because of their relative -+ electrode potentials the latter is established as the -+ cathode und thus immune to corrosion. In -+ electroplating the metal used as anode may serve as a source for replenishing the electrolyte which is consumed by cathodic deposition. The sodium-lead alloy anode used in the electrochemical production of tetraethyl lead may also be considered as a sacrificial anode. 

Electrodeposition and dissolution of magnesium film were studied from the ionic liquid of [BmimJBF with 1 MMgfCFjSOj) at room temperature by Nuli et al. [176, 177]. It was shown that magnesium can be electrodeposited on Ag substrate and the deposits were dense. They also smdied the electrochemical magnesium deposition and dissolution on metal substrates in organic electrolyte... 

NuU Y, Yang J, Wu R (2005) Reversible deposition and dissolution of magnesium from bmimbf ionic liquids. Electrochem Commun 7 1105-1110... 

Feng ZZ, Null Y, Wang JL et al (2006) Study of key factors influencing electrochemical reversibility of magnesium deposition and dissolution. J Electrochem Soc 153 C689-C693... 

An electrochemical cell consists of a silver electrode in contact with 346 mL of 0.100 M AgN03 solution and a magnesium electrode in contact with 288 mL of 0.100 M Mg(N03)2 solution, (a) Calculate E for the cell at 25°C. (b) A current is drawn from the cell until 1.20 g of silver have been deposited at the silver electrode. Calculate E for the cell at this stage of operation. 

Auger techniques have also proven useful in the characterization of electrochemically induced changes in thin-film electrodes. An example concerns films (500-2000 A thick) of magnesium phthalocyanine (MgPc) deposited over a gold contact layer on a glass substrate (106) ... 

To the list there needs to be added the very important contribution to the conversion of natural inorganic materials to useful metals by electrochemical means. Aluminium, magnesium, copper, sodium, and lithium are among the metals obtained by electrowinning. Add to this the many metals applied to solid - usually metal - surfaces by electroplating. Until the more recent vapor deposition processes, electroplating competed only with hot dipping as the means to produce duplex systems. 

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