98640 CHEMICAL ENHANCEMENT OF METALLIZED ZINC ANODE PERFORMANCE

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Product Number: 51300-98640-SG

ISBN: 98640 1998 CP

Author: Jack Bennett

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Galvanic current delivered to reinforced concrete by a metallized zinc anode was studied relative to the humidhy of its environment and periodic direct wetting, Current decreased quickly at low humidity to values unlikely to meet accepted cathodic protection criteria, but could be easily restored by direct wetting of the anode. Thirteen chemicals were screened for their ability to enhance galvanic current, Such chemicals, when applied to the exterior surface of the anode, are easily transported by capillary action to the anode-concrete interface where they serve to maintain the interface conductive and the zinc electrochemically active, The most effective chemicals were potassium and lithium bromide, acetate, chloride and nitrate, which increased galvanic current by a factor of 2-15, depending on relative humidity and chloride contamination of the concrete. This new technique is expected to greatly expand the number of concrete structures which can be protected by simple galvanic cathodic protection, The use of lithium-based chemicals together with metallized zinc anode is also proposed for mitigation of existing problems due to ASR, In this case, lithium io% which prevents or inhibits expansion due to ASK can be readdy injected into the concrete. A new process, electrochemical maintenance of concrete (EMC), is also proposed to benefit reidorced concrete structures suffering horn chloride-induced corrosion. Kevwords: anodes, alkali-silica reaction, bridges, cathodic protection, concrete, corrosion, humectant, metallize, reinforcing steel, thermal spray, zinc.