In-situ measurement of corrosion in buried pipelines using vertically measured pipe-to-soil potential

• US 10,001,436 B2
• Filed: 01/22/2014
• Issued: 06/19/2018
• Est. Priority Date: 01/22/2014
• Status: Active Grant

• Current Assignee: Southwest Research Institute
• Original Assignee: Southwest Research Institute
• Inventors: Shukla, Pavan K., Dasgupta, Biswajit
• Primary Examiner(s): Satanovsky, Alexander
• Assistant Examiner(s): Fairbanks, Brent A
• Application Number:
  US14/161,165
• Publication Number:
  US 20150204775A1
• Time in Patent Office: 1,609 Days
• Field of Search: None
• CPC Class Codes: G01N 17/006 of metals
• CPC Class Codes: G01N 17/04 Corrosion probes

Abstract

A method for in-situ measuring the corrosion rate of a corroding site on an underground metal structure buried in soil, the structure being under cathodic protection. The structure-to-soil potential at varying depths above the pipeline is measured to a depth above, but not reaching the structure. These measurements are extrapolated to obtain data representing the structure-to-soil potential at the surface of the structure under the probe. The gradient of the electrical potential at this surface is used to calculate the corrosion rate of the defect. A special probe may be used to obtain the potential measurement data.

Claims

1. A method of using a vertical probe for collecting corrosion data from a location of interest on a pipeline buried in soil, the pipeline being under cathodic protection, comprising:

drilling a vertical hole in the soil such that the hole is drilled into the ground above the location of interest, and such that its axis is perpendicular or close to perpendicular to the location of interest, and to a depth approaching but not reaching the pipeline;

placing a probe in the hole, the probe having a vertical rail, a slider attached to the rail and moveable along the length of the rail, a single reference electrode attached to the slider, a ruler also attached to the slider;

wherein the reference electrode and the ruler move with the slider and the ruler indicates the depth of the reference electrode;

positioning the reference electrode at a first position along the rail, thereby positioning the reference electrode at a first depth above the location of interest;

measuring the structure-to-soil electric potential at the first depth;

re-positioning, without removing the probe from the hole, the reference electrode to a second position along the rail, thereby positioning the reference electrode at a second depth at relative to the same location of interest;

measuring a second structure-to-soil potential at the second depth; and

repeating the re-positioning and subsequent measuring steps at least three times at varying depths until a data set representing the structure-to-soil potential at the varying depths relative to the same location of interest, over a distance of multiple feet, of the single reference electrode, to a predetermined depth not reaching the pipeline is obtained.

2. The method of claim 1 wherein the location of interest has a coating defect.

3. The method of claim 2 wherein the defect is a holiday in the coating of the pipeline.

4. The method of claim 2 wherein the defect is a disbondment in the coating of the pipeline.

5. The method of claim 1 wherein the pipeline is uncoated.