Materials Performance

NOV 2014

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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32 NOVEMBER 2014 MATERIALS PERFORMANCE NACE INTERNATIONAL: VOL. 53, NO. 11 CATHODIC PROTECTION S A thin layer of semi-conductive mate- rial was developed and combined with mixed metal oxide (MMO)-coat- ed titanium tape anodes for cathodic protection (CP) of reinforced concrete structures. This system overcomes several problems experienced with existing CP systems, including poor CP current distribution caused by near-short circuits and shallow con- crete cover; acid generation at the anode-concrete interface; and dry- ness of the anode-concrete interface for some structures. Simplifed engi- neering of the anode and installation provide a more user-friendly and cost- effective approach. Since 1980, cathodic protection (CP) has been recognized as th e most ef fective m e t h o d f o r c o n t r o l l i n g c o r r o si o n of reinforcing steel in chloride-contaminated concrete structures. Various CP systems have b e en used in over 20 c ountri e s. However, several obstacles have limited the use of this powerful technology. Obstacles to CP System Effectiveness Industry Problems • CP is often not recognized as the most effective means to control rebar corrosion. • The initial expense of applying CP systems is high. Savings realized over the lifespan of the structure are often not factored into the cost/benefit analysis. • CP experts are often not locally avail- able. • CP system complexity deters many local contractors. • CP system maintenance is perceived as a burden because it is unfamiliar to owners. Engineering Problems • S o m e e n g i n e e r s d e s i g n t h e C P syst ems without regard for cost- saving methods. • Some engineers design CP systems without consideration of long-term performance. • Inexperience can lead to CP system designs that are not practical to install. • Many CP designers copy the drawings and specifications from old projects w ithout regard to requirem ents/ differences in the new application. 1 Technical Problems • CP current distribution can be inade- quate when near-short circuits exist. • E x c e s s i v e c u r re n t d e n s i t y (C D ) generates acid at the anode-concrete interface. • Certain cementitious materials are inappropriate for use with CP. Cost Effective Cathodic Protection System for Concrete Structures Miki Funahashi, MUI International, West Chester, Pennsylvania Todd sirola and dennis McinTaggarT, SAE, Inc., Barrie, Ontario, Canada

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