is complicated by some or all of the following considerations: the metal content is low (a few percent is typical), other metals deposit competitively with the desired one, the ore is not easily or efficiently dissolved. For these reasons, electrowinning is usually only used on purified solutions of a desired metal, e.g. cyanide-extracts of gold ores. Because metal deposition rates are related to available surface area, maintaining properly working cathodes is important. Two cathode types exist, flat-plate and reticulated cathodes, each with its own advantages and disadvantages. Flat-plate cathodes can be cleaned and reused, and plated metals recovered by either mechanically scraping the cathode (or, if the electrolyzed metal has a lower melting point than the cathode, heating the cathode to the electrolyzed metal's melting point causing the electrolyzed metal to liquify and separate from the cathode, which remains solid). Reticulated cathodes have a much higher deposition rate compared to flat-plate cathodes due to their greater surface area. However, reticulated cathodes are not reusable and must be sent off for recycling. Alternatively, starter cathodes of pre-refined metals can be used, which become an integral part of the finished metal ready for rolling or further processing. See also Electrochemical engineering References External links High Throughput Electrorefining of Uranium in Pyro-reprocessing Aluminum Electrowinning and Electrorefining with Ionic Liquids How Hydrometallurgy and the SX/EW Process Made Copper the "Green" Metal Copper Electrowinning Chemical processes Electrolysis Metallurgical processes Separation processes