The external pipeline corrosion control field has seen great change over the years from
a regulatory standpoint, but very few advances in new technology to assist in monitoring the
effectiveness of mitigation efforts. Recently a new tool for the corrosion professional’s toolbox
was introduced – an in-line inspection (ILI) tool that measures cathodic protection (CP) current
flowing on a pipeline.
A.W. Peabody stated in his classic book Control of Pipeline Corrosion “When the
amount of current flowing (to the pipe) is adjusted properly, it will overpower corrosion current
discharging from all anodic areas on the pipeline and there will be a net current flow onto the
pipe surface at these points. The entire surface will then be cathodic and the protection
complete.” The cathodic protection current measurement tool is an inline inspection tool that
measures the voltage drop in the pipe wall that is caused by the accumulation and flow of
cathodic protection (CP) current. This voltage is converted to current using Ohm’s law and the
data is graphically represented. This paper will explain the benefits of this new technology and
present case histories of recent pipeline inspections.
Key words: cathodic protection, current measurement, in-line inspection