Anode efficiency

There are two parasitic reactions offsetting anode efficiency (/) cogeneration of oxygen [7782-44-7] O2, from the anodic discharge of water,... 

RoUs and other relatively simple shapes make use of inert shields and thieves to avoid edge buildup and produce a more even plate thickness. For more compUcated shapes having deeper recesses thicker deposits from cyanide copper baths have been used as an undercoat to the copper sulfate deposit. Acid copper baths operate near 100% efficient over a wide current density range. The cathode efficiency is usuaUy slightly less than the anode efficiency, bringing about a slow increase in copper unless drag-out losses are high. 

The anode efficiency is the percentage of the theoretical anode capacity that is achieved in practice ... 

Anode efficiency is of little practical significance and can be misleading. For example, magnesium alloy anodes often have an efficiency ca. 50% whilst for zinc alloys the value exceeds 90% it does not follow that zinc alloy anodes are superior to those based on magnesium. Efficiency will be encountered in many texts on sacrificial anode cathodic protection. 

In an ideal situation (and only in that ) the cathode and anode efficiencies should be equal that is, as much metal should dissolve from the anode as is being deposited at the cathode, leaving the bath in perfect or constant equilibrium. 

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. 

Faraday s Law applies to the anode as well as to the cathode ie, the total reaction at the anode is proportional to the current, and much like the cathode, the anode efficiency varies with the current density. As the current on the anode is increased, the anode efficiency decreases, slightly at first, until it reaches a point at which the anode metal cannot dissolve fast enough through the anode film. The first stage of dissolution for the soluble anode is the oxidation of the metal followed by dissolution of the oxide. When the oxide dissolution rate is less than the oxidation rate, polarization of the anode takes place. The oxide film builds up in sufficient thickness to form an insulating coating, and the current decreases rapidly. The thick anode films can dislodge at... 

How many coulombs must be supplied to a cell for the electrolytic production of 245 g NaCICU from NaClOs Because of side reactions, the anode efficiency is only 60% for the reaction. 

How many hours will it take to produce 100 lb of electrolytic chorine from NaCl in a cell that carries 1000 A The anode efficiency for the chlorine half-reaction is 85%. 

Figure 1.9. Schematic presentation showing PAFC structure and reactions with an anode efficiency of 80% [16]. (With kind permission from Springer Science+Business Media Blomen MJ, Mugerwa MN, eds., Fuel cell systems, 1993 Springer.)...

What is the hourly production rate of chlorine gas (in kg) from an electrolytic cell using aqueous NaCl electrolyte and carrying a current of 1.500 X 10 A The anode efficiency for the oxidation of Cl is 93.0 percent. 

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