Detecting faults in underground pipe corrosion protection layers - uses potential measured w.r.t. reference electrode following calibration measurement

摘要

The appts. is used for detecting fault locations in corrosion protection coatings of earth covered cast or steel pipes and can be employed with each type of coating and pipe material. The potential of a properly coated pipe is determined in a test sequence w.r.t. a reference electrode. The potential of the covered, electrically insulated pipe is then measured w.r.t. the same reference electrode and compared with the previously determined value. For pipes with a glass fibre reinforced concrete coating with additional organic sealing material a potential more negative than -500 mV w.r.t. a copper sulphate electrode would indicate the presence of a fault. For pipes with a purely organic coating on a plastic base a potential other than 0 mV would be interpreted at indicating a defect.