11005 The Response of Protective Current to Environmental Conditions During Hybrid Anode Concrete Repair Treatments

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Product Number: 51300-11005-SG

ISBN: 11005 2011 CP

Author: Steven Holmes, Gareth K. Glass, Geoffrey D. Wilcox, Peter J. Robins and Adrian C. Roberts

Publication Date: 2011

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This work examines the current response of installed ‘hybrid’ (combined impressed current and sacrificial) anodes to changes in environmental conditions and investigates the effect of this ‘responsive behavior’ on anode lifespan. The behavior reported is also discussed in terms of its correlation with the two reported models regarding the criteria for steel protection/passivity in concrete. The study showed that current passed by the installed anode was responsive to changes in temperature, moisture and concrete chloride content during both the impressed current and galvanic phases of the hybrid treatment. This meant that anode life was conserved in benign conditions and shortened when the concrete environment was aggressive. It was also seen that a high current density impressed current treatment ‘activated’ the installed anode, allowing it to pass a much higher current during the galvanic phase of the treatment. The data collected fits better with the Acidification - Pit Re-alkalization model for corrosion monitoring of steel in atmospheric concrete, rather than the Pitting Potential - Repassivation model used frequently in the industry.

Key words: Hybrid anode, sacrificial anode, re-alkalization, re-passivation, responsive behavior, galvanic, pitting, impressed current, hydroxide.