Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.
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34 OCTOBER 2017 MATERIALS PERFORMANCE NACE INTERNATIONAL: VOL. 56, NO. 10 CATHODIC PROTECTION B Corrosion of metallic pipelines is a significant source of failures and a financial burden to drinking water utilities. Cathodic protection (CP) has been a recognized technology for buried metallic pipelines for decades but has not been widely used in the water industry. Some water utilities have been exploring a variety of tech- niques to fight external corrosion and to preserve the value of their buried assets. However, a standardized and defensible approach does not exist. The effectiveness of a CP program may be measured by reduction in breakage rates. Where water utilities do not have specific data on "before and after CP" breakage rates, case studies from other water utilities with similar pipe inventories and opera- tional conditions may be used to make wise CP decisions. B a s e d o n t h e c o r r o s i o n I M PA C T (International Measures of Prevention , Application, and Economics of Corrosion Technologies) study by NACE International released in March 2016, 1 the global cost of corrosion is estimated to be US$2.5 tril- lion—equivalent to 3.4% of the global GDP. A large portion of drinking water infrastruc- ture is reaching the end of its useful service life. In the United States, the annual total of water main breaks attributed primarily to corrosion was estimated as 240,000 breaks per year. The cost of replacing over one mil- lion miles of corroded water and waste - Cathodic Protection in the Water Utility Industry Mersedeh Akhoond A n A nd Gr A h AM e .C. Bell, HDR, San Diego, California, USA water pipes was estimated at US$2.1 trillion if all pipes were to be replaced at once. 1 It was reported that 35 to 50% of this cost could have been avoided through proper design, operation, and corrosion preven- tion. 2 Implementing and maintaining effec- tive corrosion control programs are essen- tial keys for service life extension of pipe a ss e t s . A s p a r t of a n on go i n g Wat er Research Foundation project (WRF4618), technical and economic considerations for cathodic protection (CP) installation and retrofit of buried water pipelines have been investigated to generate a best practice guide tailored for water utilities. CP of metallic structures is commonly a c h i e v e d b y g a l v a n i c p r o t e c t i o n o r impressed current protection, depending on the specificities of the system. The basic concept behind CP is that applying current (in the form of electrons or charged ions) to a metallic surface can reduce the tendency of metallic ions to separate from the parent structure (usually in the form of oxides). In the United States, CP is required by regulation for gas pipelines and hazardous liquid interstate pipelines installed after the early 1970s. The U.S. Pipeline and Hazard- o u s Ma t e r i a l s S a f e ty A d m i n i st ra t i o n (PHMSA) states that, "All corrosion on un- derground metallic pipes and tanks should be considered active and pipes should be cathodically protected , repaired , or re- placed." These regulations do not apply to water utilities, as the failures in water sys- tems are typically not as catastrophic as the failure of oil and gas pipelines. However, the consequence of failures in water systems remains very high. Accordingly, water utili- ties have been exploring a variety of tech-