Zinc Anodes and Zinc Ribbon
Today, most electric power generation companies require that qualified corrosion professionals perform data collection and studies to determine the presence and degree of AC interference on crossing or parallel pipelines within AC corridors. The primary means of mitigating AC voltages on such pipelines is extruded zinc ribbon anodes.
Although the industry has experienced considerable success with the application of zinc ribbons for induced, AC and fault currents, one of the challenges has been the use of zinc ribbons in cold weather environments (typically less than 52° F). Corrpro has worked with the University of Wisconsin, the General Research Institute of Non-Ferrous Metals (GRINM) and its suppliers to develop a zinc material that is designed for challenging colder weather climates. Further, this state-of-the-art material meets the most stringent industry standards, ASTM B 4 Type II standards and is manufactured in an ISO 9000 certified facility. This superior zinc material ensures high performance and our QA/QC program is one of the
most stringent in the industry.
Zinc ribbon project AC mitigation techniques should only be employed through conscientious, professional engineering recommendations. As a leading provider of AC mitigation and cathodic protection services, Corrpro’s registered professional electrical engineers and NACE International certified corrosion specialists are available to assist with AC interference studies and AC mitigation design and construction.
Zinc anodes provide a very simple, cost-effective maintenance-free method of corrosion control for buried or immersed metals like iron, steel, aluminum, copper, etc. In a continuous ribbon form containing a steel wire core, zinc has been a highly effective and economical method of protecting a wide variety of underground and underwater metallic systems for over 20 years.
Effective Protection for Low Resistivity Environments
Zinc anodes have been used since the 19th century to protect steel structures from corrosion. Today, these anodes are still widely utilized and have proven to be an effective choice for preventing corrosion in select soils and brackish waters. For these environments, Corrpro offers zinc anodes made to the ASTM-B-418, Type II alloy standard. The anodes generate an open circuit potential of 1.1 volts with respect ot a Cu/CuSO4 reference cell. Made from 99.99% pure high-grade zinc, Corrpro zinc anodes offer a 90% current efficiency and deliver a current capacity of 335 amp-hrs/lb. This high purity composition also assures the anodes are more resistant to passive films.
Corrpro zinc anodes are available in both cast and extruded forms. The cast anodes are produced in a variety of weights and are designed for use in low-resistivity soil environments. These anodes are manufactured with lead wires and are packaged in a backfill consisting of 75% gypsum, 20% bentonite and 5% sodium sulfate. Corrpro zinc extruded anodes are produced in diamond-shaped ribbon coils. The elongated shape allows for lower resistance to earth than conventional zinc anodes and permits easy installation on a multitude of structures.
Zinc cast anodes are recommended for use in soils with resistivities below 1,000 ohm-cm. Because these anodes have a driving voltage that is lower than magnesium, they are most effective on well-coated steel structures which require minimal current output. The packaged anodes are commonly used as grounding cells on electrical motors, panels and conduits and across insulators on pipelines to limit dangerously high voltages. The extruded ribbon anode can be used in buried applications. Neither type of zinc anode should be used in extremely alkaline above 9.2pH, acidic below 5pH or high temperatures above 140˚F electrolytes. Corrpro zinc anodes are available in a variety of weights and dimensions. Zinc ribbon is typically supplied on wood spools.
Standard applications for zinc anodes include use in AC mitigation, above-ground storage tank cathodic protection, pipeline cathodic protection, grounding overhead structures have been used effectively to control corrosion of steel or other components in applications such as:
- Exterior of underground or underwater pipe
- Interior of pipe handling corrosive waters and effluents
- Lead sheathed electric cable in ducts
- Other metal-sheathed electric cable in underwater or underground locations
- Copper concentric neutrals of URD cable
- Corrosion control and/or grounding of induced AC on underground pipe
- Annulus space between outer steel casing and inner pipe of deep wells
- Interior bottoms of oil storage tanks
- Foamed annulus space of insulated steel pipe underground or underwater
- Double bottom areas of ship ballast tanks
- Bottom areas of cargo/ballast tanks of petroleum carriers