03291THE PROTECTIVE EFFECTS OF ELECTROCHEMICAL TREATMENT IN REINFORCED CONCRETE

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Product Number: 51300-03291-SG

ISBN: 03291 2003 CP

Author: Gareth Glass, John Taylor, Adrian Roberts, Nigel Davison

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In this review the relative importance of the various protective effects operating when electrochemical treatment is applied to reinforcing steel in atmospherically exposed concrete is assessed. The available evidence suggests that, on balance, the principal protective effect of a cathodic current applied to steel in atmospherically exposed concrete is to improve the environment at the steel. This promotes the formation of a stable passive film on the steel that polarises the anodic dissolution reaction. While the textbook understanding of cathodic protection suggests it cathodically polarises the steel, its ultimate effect in concrete is to cause anodic polarisation. Indeed, it can be shown that the protective effects of a negative potential shift may be negligible compared to the protective effects of improving the environment at a steel cathode in atmospherically exposed concrete where oxygen access is not restricted. Electrochemical treatment may also modify the solid phases present at the steel surface, which in turn results in a persistent increase in the tolerance to the presence of chloride ions. The effect of generating a protective environment at the steel has been observed in both galvanic and impressed current electrochemical protection systems applied to reinforced concrete. Keywords: cathodic protection, concrete, corrosion, criteria, chloride extraction, realkalisation, sacrificial anodes