Contactless Magnetic Inspection Technology on Pipelines with High Shielding Dielectric Polyethylene Coatings

Do you know there is now a proven solution for detecting external corrosion beneath disbonded coatings on buried pipelines coated with high‑dielectric polyethylene wrap shielding systems?

High‑dielectric and shielding coatings—such as improperly applied polyethylene tape—tend to electrically isolate disbonded regions, preventing applied cathodic current from effectively reaching the steel surface underneath.
In these systems, the migration of moisture and electrolytes beneath disbonded coating layers can create active corrosion cells on the steel surface, even when the pipeline appears adequately protected based on conventional cathodic protection (CP) surveys such as Cathodic Protection Close Interval Surveys (CP CIPS).

As a result, traditional indirect inspection methods are limited in their ability to detect or confirm corrosion activity beneath shielding coatings.

Contactless Magnetic Inspection Technology (CMIT) overcomes these limitations by directly sensing magnetic field distortions associated with metal loss and stress concentration from aboveground, without requiring electrical contact with the pipeline. CMIT serves as a powerful complementary tool to CP monitoring and Direct Current Voltage Gradient (DCVG)/CP CIPS surveys, providing valuable confirmation of actual corrosion conditions beneath disbonded or shielding coatings.

Download our case study below, where we validated CMIT’s ability to identify external corrosion and other pipeline defects in a 20‑in nominal diameter, high‑pressure, underground natural gas pipeline.