Chromium, electrodeposition

Practices for preparation of and electroplating on Chromium (Electrodeposits) on Chromium Copper and Copper-Base Mllojs Iron Castings Eead and EeadMllojs Magnesium and Magnesium Mllojs Molybdenum and Molybdenum Mlloys MickelMlloys... 

This rather useful empirical expression is applicable to many electrodeposited materials [e.g., molybdenum, zinc, steel (10)]. The expression has been able, for instance, to provide an acceptable explanation for the phenomenon of the brittle cracking in chromium electrodeposits. It has been quite helpful in the general study and understanding of the functional connection between hardness and grain size values in many electrodeposits. 

Nickel Domestic use and engineering Undercoat for chromium electrodeposition... 

Chromium electrodeposits can also be obtained from electrolytes containing acetone and chromium chloride at current densities of 0.1-1 A/dm and 15 °C. Nickel-chromium alloy coatings with up to 22% chromium can be deposited out of... 

Thin coatings of chromium [139] are applied over another electrodeposited layer, usually nickel or copper, as a decorative, nonstaining finish these thin (250 pm) layers are porous. Hard chromium plating is used where advantage may derive from the high hardness and wear resistance, or the low coefficient of friction, of such deposits. Chromium electrodeposits are not suitable for use at high... 

Chromium plating from chromic acid baths is more sensitive to the source of current than most other processes, sufficiently so for commercial operators to use at least three-phase rectifiers as a rule, and to take precautions against any temporary break of current during voltage regulation. A recent investigation showed that the ripple introduced by thyristor control of rectifiers was detrimental to chromium electrodeposits. 

Petrovic BM, Kostic TM (2000) The properties of chromium electrodeposited with programed currents. Part 1 direct current. J Serb Chem Soc 65 55-63... 

Mcdougall J, EL-Shrif M, Ma S (1998) Chromium electrodeposition using a chromium(in) glycine complex. J Appl Electrochem 28 929-934... 

Aqueous Electrodeposition. The theory of electro deposition is well known (see Electroplating). Of the numerous metals used in electro deposition, only 10 have been reduced to large-scale commercial practice. The most commonly plated metals are chromium, nickel, copper, zinc, rhodium, silver, cadmium, tin, and gold, followed by the less frequendy plated metals iron, cesium, platinum, and palladium, and the infrequendy plated metals indium, mthenium, and rhenium. Of these, only platinum, rhodium, iddium, and rhenium are refractory. 

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. 

A.STM B456, Std. Spec, for Electrodeposited Coatings of Copper Plus Nickel Plus Chromium and Nickel Plus Chromium, American Society for Testing and Materials, Philadelphia, Pa., 1993. 

Nickel, chromium and zinc are commonly used as electrodeposits. Chromium, the hardest of these coatings, is applied for abrasion resistance... 

Nickel is also widely used as an electrodeposited underlay to chromium on chromium-plated articles, reinforcing the protection against corrosion provided by the thin chromium surface layer. Additionally the production of articles of complex shape to close dimensional tolerances in nickel by electroforming —a high-speed electrodeposition process —has attracted considerable interest. Electrodeposition of nickel and the properties of electro-deposited coatings containing nickel are dealt with in greater detail in Section 14.7. 

Gold coatings on separable electric contacts and slip rings make use of the high hardness possible with electrodeposition to resist wear. Rhodium is another metal which can be exceptionally hard. Thick coatings have a cracked-sealed structure similar to that of chromium. 

Chromium is also a very hard metal with excellent wear resistance, and so is widely used as a coating material for engineering applications. For these purposes, coatings are applied by electrodeposition which may be several millimetres thick. These hard engineering chromium coatings invariably contain fine cracks and fissures which can allow corrodents to attack the... 

Engineering electrodeposits Engineering electrodeposits are used to give improved properties on new components, or to replace metal lost by wear, corrosion or mis-machining, or as an undercoat for thick chromium deposits. 

Wearmouth has described the production of nickel-cobalt, nickel-manganese, and nickel-chromium alloy coatings for non-decorative uses. The nickel-cobalt and nickel-manganese are electrodeposited direct from sulphamate-based solutions, the nickel-cobalt alloys offering higher hardness than the nickel-manganese alloys, which are restricted to a relatively... 

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