State of Art for “Phase Sensitive Methods to Detect Cathodic Disbondment”

This document serves as a state of the art for technologies used to detect cathodic disbondment on steel pipe. The object of the proposed work is to develop a technology that could detect coating disbondment on steel pipe from above ground, thus identifying potential corrosion locations before the pipeline fails. Ideally this technology would detect a coating disbondment at a very early stage, when there is little or no corrosion associated with it. There is currently no method to detect or locate a disbonded coating from above ground. Existing pipeline potential gradient surveys, both DC and AC voltage, make use of only amplitude data. While amplitude methods can detect an active holiday (break) in the coating, a disbonded coating can shield active corrosion from both detection and cathodic protection. Stated another way, the space between a disbonded coating and the pipe can house an active corrosion cell. Until there is an actual holiday in the coating, the corrosion cell cannot be detected with existing technology. A holiday will allow increased cathodic protection current to flow to the pipe in the immediate vicinity of the holiday, but may not reach the extremities of a large disbondment. Internal methods, such as magnetic flux leakage (MFL) pigging may detect wall thinning but will not differentiate causes. MFL pigging is expensive and may not be possible on lines with bends or diameter changes. A patent search was performed, and no technologies relating to Phase Sensitive Methods to Detect Cathodic Disbondment were found. There are, however, other technologies that may detect cathodic disbondment by other means. There are also techniques that may infer the presence of cathodic disbondment by detecting its effects, such as shielded corrosion cells. The general result of the state-of-the-art survey is that there is a great deal of technology that is focused on identifying and locating active corrosion. There is little technology that can identify flaws early on.

  • Record URL:
  • Corporate Authors:

    Gas Technology Institute

    1700 South Mount Prospect Road
    Des Plaines, IL  United States  60018

    Pipeline and Hazardous Materials Safety Administration

    Department of Transportation
    East Building, 2nd Floor, 1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Authors:
    • McCarty, Joe
  • Publication Date: 2006-11

Language

  • English

Media Info

  • Media Type: Digital/other
  • Features: Appendices; Figures; References; Tables;
  • Pagination: 152p

Subject/Index Terms

Filing Info

  • Accession Number: 01848879
  • Record Type: Publication
  • Contract Numbers: DTPH56-06-T-000020
  • Files: NTL, TRIS, ATRI, USDOT
  • Created Date: Jun 20 2022 5:56PM