During a prior research program, a spiking phenomenon was identified that prevented the measurement of the off potential directly from the pipe-to-soil potential waveform. Furthermore, the spike made it impossible to measure an off potential during current interruption for some period of time following interruption. In recent years, there has been discussion that the spike in the pipe-to-soil potential waveform affects the ability of the CP system to mitigate corrosion. In addition, the increased significance that has been placed on off-potential measurements within the industry has made it important...
During a prior research program, a spiking phenomenon was identified that prevented the measurement of the off potential directly from the pipe-to-soil potential waveform. Furthermore, the spike made it impossible to measure an off potential during current interruption for some period of time following interruption. In recent years, there has been discussion that the spike in the pipe-to-soil potential waveform affects the ability of the CP system to mitigate corrosion. In addition, the increased significance that has been placed on off-potential measurements within the industry has made it important to understand any phenomenon that may affect the ability to measure the off potential. This effort works to establish the cause and effects of the spiking phenomenon. To accomplish this program, a Work Plan was established that provided for the following four tasks: Task 1 - Field Measurements, Task 2 - Circuit Analog Model, Task 3 - Effect of the Spike on Off- Potential Measurements, and Task 4 - Laboratory Experiments. Through this combined effort of field evaluations, modeling, and laboratory experiments, the root cause of the spike was established along with guidelines for making the off-potential measurement. The results of this project provides the CP engineer with a standard practice for measuring off-potentials in the presence of the spiking phenomenon.