Corrosion rate measurement of multiple reinforcements using the galvanostatic pulse technique with the guard ring

This study investigates the corrosion rate measurements for multiple reinforcements in concrete by using the galvanostatic pulse technique. In order to know whether or not this technique can distinguish corrosion status for multiple reinforcements covered by the guard ring, two programs were conducted. For the first stage, a reinforcement was embedded in two concrete blocks and the part of reinforcement in one of the block was in a corrosion environment while another part of reinforcement in another block was not in a corrosion environment. Results reconfirmed that the galvanostatic pulse technique detected the local corrosion current owing to the help from guard ring. For the second stage, two parallel reinforcements (one epoxy-coated reinforcement and one plain reinforcement) were embedded in a chloride contaminated concrete block. Results showed that when two reinforcements were covered by guard ring, the galvanostatic pulse technique could not distinguish the corrosion current for each individual reinforcement and an average value would be obtained. In such a case, for the reinforcement which was not corroded one may overestimate its corrosion rate, and for the reinforcement which was corroded one may underestimate its corrosion. Therefore, results imply that a C-scan method (which is commonly used for the ultrasonic testing) may be required to obtain a correct measurement of corrosion rate.