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Hexavalent chromium plating

Composite Coatings as a Substitute for Hexavalent Chromium Plating... [Pg.268]

Benaben, P. Sottil, B. (2006), Hard Chromium deposition using ionic liquids as a potential substitute to hexavalent chromium plating First results in European lONMET programme 57-th Annual Meeting of ISE, Edinburgh, 2006, Abstracts, S5-0-3. [Pg.284]

Conroy LM, Wadden RA, Scheff PA, Franke JE, Keil CB. Workplace emission factors for hexavalent chromium plating. Appl Occup Environ Hyg 1995 10 620-627. [Pg.165]

Neutralizing removes the large amount of hexavalent chromium from the surface of the part. Hexavalent chromium shortens the life of the catalyst, and trace amounts completely inhibit electroless nickel deposition. The neutralizer is usually a mildly acidic or basic reducing agent, but other types of neutralizers are available, especially for substrates that are difficult to plate. The neutralizer may also contain surfactants (qv) or other compounds that increase catalyst absorption absorption promoters are often needed for non-ABS plastics. [Pg.110]

Decorative plating primarily over bright nickel is estimated to consume about 2270 t worldwide. Some 60% of this is used in North America, and about 900 t in Europe. A relatively new method in decorative chromium plating is based on trivalent instead of hexavalent chromium, and this is estimated to total about 10% of the decorative market and is expected to increase. Chromic acid, which cost about 2.76/kg in early 1993, is the hexavalent... [Pg.143]

Examples of plating solutions having good throwing power include cyanide plating baths such as copper, zinc, cadmium, silver, and gold, and noncyanide alkaline zinc baths. Examples of poorer throwing power baths are acid baths such as copper, nickel, zinc, and hexavalent chromium. [Pg.146]

Chromium (hexavalent) in chromium plating mists Colorimetric field method using 1,5-diphenylcarbazide 52/3... [Pg.361]

Chromium plating from hexavalent baths is carried out with insoluble lead-lead peroxide anodes, since chromium anodes would be insoluble (passive). There are three main anode reactions oxidation of water, reoxidation of Cr ions (or more probably complex polychromate compounds) produced at the cathode and gradual thickening of the PbOj film. The anode current density must balance the reduction and reoxidation of trivalent chromium so that the concentration reaches a steady state. From time to time the PbOj film is removed as it increases electrical resistance. [Pg.349]

Concern over the health hazards of the hexavalent chromium solutions used to form the top coat of conventional nickel plus chromium coatings have encouraged research into trivalent chromium plating solutions. A process with better throwing power and improved covering power than those of hexavalent chromium has been described by Smart etal". A process for depositing a chromium-iron, or chromium-nickel-iron alloy, has been outlined by Law. ... [Pg.540]

Hexavalent chromium in chromium plating mists (supersedes EH 6 and MDHS 52/2 1990)... [Pg.581]

FIGURE 6.2 Rate of reduction of hexavalent chromium in the presence of excess S02 at various pH levels. (Taken from Krofta, M. and Wang, L.K., Design of Innovative Flotation-Filtration Wastewater Treatment Systems for a Nickel-Chromium Plating Plant, U.S. Department of Commerce, National Technical Information Service, Springfield, VA, Technical Report PB-88-200522/AS, January 1984.)... [Pg.243]

Alternatively, hexavalent chromium can be reduced, precipitated, and floated by ferrous sulfide. By applying ferrous sulfide as a flotation aid to a plating waste with an initial hexavalent chromium concentration of 130 mg/L and total chromium concentration of 155 mg/L, an effluent quality of less than 0.05 mg/L of either chromium species can be achieved if a flotation-filtration wastewater treatment system is used.15... [Pg.245]

Ferrous sulfide acts as a reducing agent at pH 8 to 9 for reduction of hexavalent chromium and then precipitates the trivalent chromium as a hydroxide in one step without pH adjustment.5162 So, the hexavalent chromium in the nickel-chromium plating wastewater does not have to be isolated and pretreated by reduction to the trivalent form. The new process is applicable for removal of all heavy metals. All heavy metals other than chromium are removed as insoluble metal sulfides, M(II)S. [Pg.245]

The newly developed flotation-filtration process involving the use of ferrous sulfide as a flotation aid offers a distinct advantage in the treatment of nickel-chromium plating wastewater that contains hexavalent chromium, nickel, iron, and other metals. [Pg.245]

Bishara JI, Brannan JR, Dickie DK, Horvath RJ, Recovery of hexavalent chromium from plating rinse waters, in ref (45)... [Pg.233]

Unlike nickel, chromium metal does not produce allergic contact dermatitis. Some patients exhibit positive patch tests to divalent chromium compounds, but these compounds are considerably less potent as sensitizers than hexavalent chromium compounds. A case of chromium (chromic) sulfate-induced asthma in a plating worker, confirmed by specific challenge testing and the presence of IgE antibodies, has been reported. ... [Pg.173]

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See also in sourсe #XX -- [ Pg.132 ]



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