Electrodeposition electrolytes

Covering power describes the extent to which an electrodeposition electrolyte can cover the entire surface of a workpiece being plated, with reasonable uniform thickness. Covering power is influenced by the nature of the substrate surface, the electrolyte composition, the temperature and viscosity, and the current density. 

Electrodeposition - Electrolytic process in which a metal is deposited at the cathode from a solution of its ions. 

Electrodeposition - Electrolytic reduction of plutonium at a platinum cathode. Preparation of sources for energy analysis. Very thin, uniform films arc attainable. Method can be made quantitative. Requires special preparation of solution, requires relatively long time to prep2irc 1 sample. 

The ionic liquids have some properties which make them adequate as metal electrodeposition electrolytes, such as ... 

Toxic substances adsorbed on resins are removed during a regeneration procedure. The resulting spent regeneration solution has a higher concentration of the toxic substance than the stream from which it was removed by the resin. Toxic material in the spent regenerating solution can usually be precipitated, electrodeposited as in an electrolytic ceU, or made insoluble by other acceptable procedures. 

Solvent for Electrolytic Reactions. Dimethyl sulfoxide has been widely used as a solvent for polarographic studies and a more negative cathode potential can be used in it than in water. In DMSO, cations can be successfully reduced to metals that react with water. Thus, the following metals have been electrodeposited from their salts in DMSO cerium, actinides, iron, nickel, cobalt, and manganese as amorphous deposits zinc, cadmium, tin, and bismuth as crystalline deposits and chromium, silver, lead, copper, and titanium (96—103). Generally, no metal less noble than zinc can be deposited from DMSO. 

Electrodeposition. Electro deposition, the most important of the unit processes in electrorefining, is performed in lead- or plastic-lined concrete cells or, more recently, in polymer—concrete electrolytic cells. A refinery having an aimual production of 175,000 t might have as many as 1250 cells in the tank house. The cells are multiply coimected such that anodes and cathodes are placed alternately and coimected in parallel. Each cell is a separate unit and electrically coimected to adjacent cells by a bus bar. 

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]. 

In the field of electrowinning and electrorefining of metals, titanium has an advantage as a cathode, upon which copper particularly can be deposited with finely balanced adhesion that allows the electrodeposited metal to strip easily when required. Titanium anodes are also being employed as a replacement for lead or graphite in the production of electrolytic manganese dioxide. 

Pt electrodeposits may also be produced from molten salt electrolytes. Such a high-temperature process has the advantage that the deposits are diffusion bonded to the titanium substrate and thus have good adhesion, and, if necessary, thick deposits can be produced. However, they have the disadvantage that because of the complexity of the process there is a limitation on the size and shape of the object to be plated, and the resultant deposits are softer and less wear resistant than those from aqueous solutions... 

Brush plating is a special technique which dispenses with a container and uses a swab soaked in electrolyte applied to the work. In jet plating a stream of electrolyte is applied to the cathode. Both are methods of selective plating, applying an electrodeposit to only a part of an article. Little has been published about the techniques or the properties of coatings they produce. 

Immersion in aqueous media open to air Solutions in which tin is cathodic to steel cause corrosion at pores, with the possibility of serious pitting in electrolytes of high conductivity. Porous coatings may give satisfactory service when the corrosive medium deposits protective scale, as in hard waters, or when use is intermittent and is followed by cleaning, as for kitchen equipment, but otherwise coatings electrodeposited or sprayed to a sufficient thickness to be pore-free are usually required. 

Resistance to corrosion Most authors who compare resistance to corrosion of electroless nickel with that of electrodeposited nickel conclude that the electroless deposit is the superior material when assessed by salt spray testing, seaside exposure or subjection to nitric acid. Also, resistance to corrosion of electroless nickel is said to increase with increasing phosphorus level. However, unpublished results from International Nickel s Birmingham research laboratory showed that electroless nickel-phosphorus and electrolytic nickel deposits were not significantly different on roof exposure or when compared by polarisation data. 

Electrodeposited chromium, both decorative and hard , is produced with the use of a solution of chromic acid containing a small amount of catalyst which is usually sulphuric acid, although fluosilicic or fluoboric acid may be used. A typical electrolyte contains 250-400 g/1 of chromic acid and... 

The voltage used is 4-8 V, current density 9-22 A/dm, and temperature 38-43°C. Higher current densities, up to 55 A/dm, are used for thick deposits. A considerable amount of heat is generated during electrodeposition and provision must be made for cooling of the electrolyte during operation. 

For ruthenium, electrolytes based on ruthenium sulphamate or nitrosyl-sulphamate have been described, but the most useful solutions currently available are based on the anionic complex (H2 0 Cl4 Ru N Ru-Cl4-OH2) . The latter solutions operate with relatively high cathode efficiency to furnish bright deposits up to a thickness of about 0-005 0 mm, which are similar in physical characteristics to electrodeposited rhodium and have shown promise in applications for which the latter more costly metal is commonly employed. Particularly interesting is the potential application of ruthenium as an alternative to gold or rhodium plating on the contact members of sealed-reed relay switches. 

Electrodeposited chromium coatings. Electrolytic corrosion testing Coatings cathodic to the substrate-rating of electroplated test specimens subjected to corrosion tests... 

Electrodeposition deposition of a metal or alloy onto a substrate by electrochemical reduction of its ions from an electrolyte under the application of a cathodic overpotential. 

Use of low-temperature molten systems for electrolytic processes related with tantalum and niobium and other rare refractory metals seems to hold a promise for future industrial use, and is currently of great concern to researchers. The electrochemical behavior of tantalum, niobium and titanium in low-temperature carbamide-hilide melts has been investigated by Tumanova et al. [572]. Electrodeposition of tantalum and niobium from room/ambient temperature chloroaluminate molten systems has been studied by Cheek et al. [573],... 

Zinc is electrodeposited from the sodium zincate electrolyte during charge. As in the zinc/bromine battery, two separate electrolytes loops ("posilyte" and "nega-lyte") are required. The only difference is the quality of the separator The zinc/ bromine system works with a microporous foil made from sintered polymer powder, but the zinc/ferricyanide battery needs a cation exchange membrane in order to obtain acceptable coulombic efficiencies. The occasional transfer of solid sodium ferrocya-nide from the negative to the positive tank, to correct for the slow transport of complex cyanide through the membrane, is proposed [54],... 

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