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Emerald Group Publishing Limited
Copyright © 2000, MCB UP Limited
Keywords BAC Corrosion Control, Cathodic protection
Increased life and fewer replacements due to the manufacturing process are the major benefits claimed from BAC Corrosion Control's new Isoline magnesium sacrificial anodes. Extruding the magnesium, rather than casting, is thought to give a smooth surface finish resulting in uniform anode consumption and increased operational efficiency, leading to a greatly improved cathodic protection system.
BAC has two magnesium anode types, BAC Isomag, with an electrical potential of 1.7 volts for older and less well coated pipelines and buried structures, and BAC Isorod with an EP of 1.5 volts for well coated pipelines and soils with a low resistivity (Plate 3). For application in high resistivity soils, Isomag 1.7-volt anodes are recommended as they provide a higher driving voltage. Both types are manufactured from virgin magnesium alloys and are supplied in 18 standard sizes, ranging in weight from 1.3-27.3kg to cater for today's most commonly used sizes. Integral electrical cables are either 6mm2 or 10mm2 XLPE/PVC.
Plate 3 BAC has two magnesium anode types, BAC Isomag with an EP of 1.7V in red bags and Isorod with an EP of 1.5V in grey bags. Bags are backfilled to get the anodes working as soon as they are placed and connected
All the anodes are supplied in readily identifiable cotton bags – Isomag in red and Isorod in grey which are backfilled with a mixture of 75 per cent gypsum, 20 per cent bentonite and 5 per cent sodium sulphate. The advantage of supplying with a "built-in" backfill is that, as soon as the anodes are placed in the ground and electrically connected to whatever they are protecting, they begin to work.
For applications where flexible anodes are required Isomag and Isorod anodes are available in ribbon form. Ribbon anodes are for specialised applications such as the protection of external tank bases and pipelines inside sleeved crossings.
Further details are available from BAC Corrosion Control. Tel: +44 (0) 1952 290321; Fax: +44 (0) 1952 290325. Denmark: Tel: +45 70 26 89 00; Web site: www.bacgroup.com