A variety of electromagnetic methods have been developed for the assessment of condition and corrosion in metal pipes – especially for use in critical and high value pipeline infrastructure such as oil and gas pipelines. Individual methods including magnetic flux, magnetic tomography, broadband electromagnetic, eddy current testing and remote field transformed coupling (RTFC), will not be specifically described here but they are able to use the spatial response to electromagnetic stimuli within the pipe wall and/or along the pipe length to determine information such as areas of pipe wall thickness loss, presence of cracks in the pipe wall, changes in material properties such as graphitization, etc. The methods vary in terms of their need for direct access to the pipe wall to make measurements.
Using an electromagnetic method in non-conducting pipelines also is possible. For example, in the Electroscan® method, electrodes are passed through the interior of a water-filled section of a non-conducting pipe material (e.g. clay or concrete pipe). Where the pipe is sound and there are no leaks to the external ground, the current flow through the pipe wall to an external electrode in the ground is small. Where a leak exists, a higher current will flow with the increase in current flow being related to the severity of the leak.