There is a possibility that alternating current will cause corrosion in a defect of the coating on buried steel pipeline. In this research, we developed an evaluating method with which we could evaluate alternating current corrosion of the steel in a short time compared with conventional evaluating method by mesuring corrosion weight loss. The results of this research showed that alternating current corrosion of buried steel under catholic protection could be estimated by measuring the

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... ree potential, especially peak (maximum) potential of the steel using IR-dropfree probe. It was also found that corrosion protection of the steel could be achieved when peak potential of the steel was over 100mV less noble than free corrosion potential of the steel.