New method and mobile testing system for inspecting light poles and corrosion under pipe supports using guided ultrasonic waves

Light poles are exposed to corrosion from road salt, stray electrical currents, and aggressive soil conditions. This corrosion is often invisible to the naked eye, yet the resulting loss of wall thickness can severely reduce the pole's structural strength and stability. The most critical corrosion zone is located directly around the ground surface, where access is limited. Remaining wall thickness is therefore a decisive parameter for assessing structural integrity and bending strength. Conventional ultrasonic methods cannot inspect these vulnerable underground areas. A similar limitation exists for the detection of corrosion under pipe supports (CUPS), where defects are also hidden and inaccessible to traditional non-destructive testing. The proposed method overcomes these limitations by using guided ultrasonic waves propagating over long distances in confined structures and reliably identify corrosion-related wall- thickness losses. Low-frequency dry-point-contact (DPC) transducers generate a shear-horizontal wave traveling along the pipe axis, reflects from corroded regions, and is received again by the same array. DPC transducers allow measurements without couplant and require no surface preparation such as paint or rust removal. As the transducer is moved manually or by a manipulator around the circumference, the device records the reflected signals and visualizes corrosion indications in real time as an ultrasonic B- scan.