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Impressed Current Anodes-7

Elsevier Inc.
DOI: 10.1016/b978-088415056-5/50014-9


Publisher Summary Impressed current anodes can deliver a much higher current supply when anodic redox reactions run in parallel. Impressed current anodes, which are connected to the protected object from a dc source, in operation often have a more positive potential than the protected object. Materials for impressed current anodes should not only be of as low solubility as possible, but should also not be damaged by impact, abrasion, or vibration. They should also have high conductivity and be capable of heavy loads. There are two types of impressed current anodes: (1) anodically stable noble metals and (2) anodically passivatable materials that form conducting oxide films on their surfaces. In both cases, the anodic redox reaction occurs at much lower potentials than those of theoretically possible anodic corrosion. Impressed current anodes must be insulated from the surface that is being protected. Also, the current connections must be well insulated to prevent the free ends of the cable from being attacked and destroyed. The demands on insulating materials in soil and fresh water are relatively low. Anodically evolved oxygen makes the use of aging–resistant insulating materials necessary. These consist of special types of rubber (neoprene) and stabilized plastics of polyethylene and polyvinylchloride, as well as cast resins such as acrylate, epoxy, polyester resin, and many others.

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