Noncyanide baths

Noncrystalline polymers, 9 554 Noncyanide baths, 9 804-805 Noncyclic maleyl chloride, 15 485—486 Noncyclopentadienyl compounds, covalent, 25 105-109... 

Substrate (Ni)-catalyzed electroless gold deposition from a noncyanide bath containing thiosulfate and sulfite I. Reaction mechanism, M. Kato, J. Sato, H. Otani, T. Homma, Y. Okinaka, T. Osaka, and O. Yoshioka, J. Electrochem. Soc., 2002, 149, C164. 

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. 

Replace cyanide process baths with noncyanide process baths to simplify the treatment... 

Chandran et al. have intensively studied electrodeposition of zinc on steel from noncyanide plating bath [417] and bromide electrolytes [418, 419]. 

Anodes. There are two types of anodes soluble and insoluble. Most electroplating baths use one or the other specifically however, a few baths use either or both. Chromic acid plating baths use insoluble anodes alkaline zinc cyanide baths use both noncyanide alkaline zincs may use either. Soluble anodes are designed to dissolve efficiendy with current flow and preferably, not to dissolve when the system is idle. A plating solution having the anode efficiency close to the cathode efficiency provides a balanced process that has fewer control problems and is less cosdy. If the anode efficiency is much greater than the cathode efficiency and there are only small solution losses, the dissolved metal concentration rises until at some time the bath has to be diluted back or the excess metal has to be reduced by some other means. If the anode efficiency is less than the cathode efficiency, the dissolved metal decreases, pH decreases, and eventually metal salt additions and other solution corrections are required. Based on the cost of metal, it is usually considerably more economical to plate from the anode rather than add metal salt. Copper cyanide, for example, costs about twice as much to add than to dissolve a comparable amount of copper anode. Additionally, the anion added with the metal salt may build up in the plating solution. 

For general zinc plating in the United States, estimates of the zinc baths in use in 1970 showed cyanide at over 90%, chloride at 3%, and noncyanide alkaline (zincate) baths at 4%. By 1990, cyanide zinc was 20%, chloride 50%, and zincate 30% (138). In 1992 (139) the cyanide was 16%, chloride 48%, and zincate 36%. Moreover, the cyanide zinc baths of 1992 were more likely to be run at 15—30 g/L sodium cyanide in contrast to the 100 g/L normal in 1970. Each of the three zinc systems uses proprietary brighteners. 

From a practical viewpoint, the significance of the thiosulfate bath lies in the fact that it is a noncyanide, near-neutral pH system, and that it is not sensitive to nickel... 

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