Sensors for detecting early defects in pipelines and for detecting corrosion on pipelines, namely, for sensing of flux exclusion of remnant magnetic field caused due to localised wall loss in carbon steel pipes or pipelines; Detector devices for detecting early defects in pipelines and for detecting corrosion on pipelines, namely, for sensing of flux exclusion of remnant magnetic field caused due to localised wall loss in carbon steel pipes or pipelines; Monitoring devices for monitoring earl...