Abstract: A measuring and assessing method for the AC corrosion risk of a pipeline wherein the coupon is connected to a metallic pipeline buried in the earth and the AC corrosion risk of the pipeline is assessed on the basis of coupon DC current density and coupon AC current density that are acquired from a measured value of a coupon current, wherein the measuring and assessing method includes: a step of specifying frequency to specify a source of AC corrosion from a waveform of the measured value of the coupon current; and a step of calculating a coupon current density whereby a pair of coupon DC current density and coupon AC current density is acquired from the measured value of the coupon current in one time unit by defining one cycle of a specified frequency as one time unit.

Abstract: A measuring and assessing method for the AC corrosion risk of a pipeline wherein the coupon is connected to a metallic pipeline buried in the earth and the AC corrosion risk of the pipeline is assessed on the basis of coupon DC current density and coupon AC current density that are acquired from a measured value of a coupon current, wherein the measuring and assessing method includes: a step of specifying frequency to specify a source of AC corrosion from a waveform of the measured value of the coupon current; and a step of calculating a coupon current density whereby a pair of coupon DC current density and coupon AC current density is acquired from the measured value of the coupon current in one time unit by defining one cycle of a specified frequency as one time unit.

Abstract: A method and a device to assess the adequacy of a cathodically protected underground pipeline with consideration of AC corrosion. A steel probe and a CSE are installed near the pipeline at a depth. The steel probe is electrically connected to a pipeline. The measurements of AC probe currents flowing between a steel probe (2) and the pipeline (1) are per-formed simultaneously with those of on-and off-potentials, and DC probe currents.