|
Written by tom
|
|
Sunday, 22 June 2008 |
Metals used for the positive terminals in electroplating. They provide in whole or in part the source of the metal to be plated, and they are as pure as is commercially possible, uniform in texture and composition, and have the skin removed by machining.
They may be either cast or rolled, with the manufacture controlled to obtain a uniform grade and to exclude impurities, so that the anode will corrode uniformly in the plating bath and will not polarize to form slimes or crusts. In some plating, as for white bronze, the anode efficiency is much higher than the cathode efficiency, and a percentage of steel anodes is inserted to obtain a solution balance. In other cases, as in chromium plating, the metal is taken entirely from the solution, and insoluble anodes are employed. Chromium-plating anodes may be lead-antimony, with 6% antimony, or tin-lead, with 7% tin. In addition to pure single metals, various alloys are marketed in anode form. The usual brass is 80% copper and 20 zinc, but other compositions are used, some containing 1 to 2% tin. Brass anodes are called platers' brass. Abaloy anodes, of the Hanson-Van Winkle-Munning Co., for silvery-white plating, are of copper, tin, and zinc. Nickelex, used in England as a plating undercoat for aluminum, contains 90% copper and 10 tin. Copper anodes for metal plating are usually hot-rolled oval-shaped bars, 99.9% pure, while those for electrotype deposits may be hot-rolled plates, electrodeposited plates, or cast plates. The copper ball anodes of the Udylite Corp. are forged instead of cast to give a finer and more even grain. Zinc anodes are 99.99% pure. Nickel anodes are 99+% rolled or cast in iron molds, or 97% sand-cast. Bright nickel anodes may have 1% or more of cobalt. Lead anodes have low current-carrying capacity, and may be made with a sawtooth or multiple-angled surface and ribs to provide more area and give greater throwing power. Anodes of other metals are also made with sections gear-shaped, fluted, or barrel-shaped to give greater surface area and higher efficiency. Rhodium anodes are made in expanded-mesh form. Platinum anodes, also made in mesh form, have the platinum clad on tantalum wire. Special anode metals are marketed under trade names, usually accenting the color, hardness, and corrosion resistance of the deposited plate.
|
|
Last Updated ( Sunday, 22 June 2008 )
|
