In-situ Corrosion Rate Estimation via Vertical Potential Profiling
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Solution Overview
Problem
Current methods for detecting corrosion on buried pipelines, such as cathodic protection, are inadequate as they fail to prevent corrosion at coating defects and disbonded areas, making it challenging to accurately assess in-situ corrosion rates due to the inaccessibility of these structures.
Innovation Solution
The method involves vertically measuring pipe-to-soil potential using a specialized probe and analysis unit to estimate corrosion rates by calculating the current and potential distribution in the soil, allowing for the detection of coating defects and disbondment sites without exposing the pipeline, suitable for both galvanic and impressed-current protected pipelines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cathodic protection techniques are applied to buried pipelines, then corrosion resistance is improved, but the ability to detect and measure corrosion rates at coating defects deteriorates due to inaccessibility of the pipeline surface
Solution Approach 1:
The patent introduces a specialized probe as an intermediary device that can be inserted into the soil above the buried pipeline. This probe contains a reference electrode and measurement circuitry that allows indirect measurement of pipe-to-soil potential without requiring direct access to the pipeline surface. The probe acts as a mediator between the measurement system and the buried pipeline, enabling corrosion rate estimation at coating defects while the pipeline remains in situ under cathodic protection.
2Measurement precision
If vertical measurements of pipe-to-soil potential are performed using a probe, then measurement precision of corrosion rates is improved, but device complexity increases due to the specialized probe and analysis unit requirements
Solution Approach 1:
The patent extracts the measurement function into a separate, portable probe device that can be independently operated. The probe contains only the essential components needed for vertical potential measurements (reference electrode, connection terminals), while the complex analysis and calculation functions are separated into a post-processing analysis unit. This extraction allows the measurement device itself to remain simple and field-deployable, while achieving high measurement precision through sophisticated data analysis of the vertical potential profile.
3Ease of operation
If special techniques are developed for detecting coating defects without exposing the pipe surface, then ease of operation is improved, but loss of information occurs due to inability to directly observe corrosion conditions
Solution Approach 1:
The patent transitions from traditional horizontal surface inspection methods to vertical depth-based measurements. By inserting the probe vertically into the soil and measuring pipe-to-soil potential at multiple depths, the system creates a vertical profile that provides information about corrosion conditions at different soil depths above the pipeline. This dimensional change enables detection of coating defects and disbonded areas through the soil medium, maintaining ease of operation while reducing information loss about actual corrosion conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables accurate in-situ estimation of corrosion rates at buried pipeline defects, enhancing the integrity management of pipelines by identifying areas of corrosion without damaging the pipeline or disrupting the cathodic protection system.
Implementation Method 1
measurements of pipe-to-soil potential for such purposes
Implementation Method 2
Another type of cathodic protection technique uses impressed currents; a current is applied to the pipeline to force the pipeline surface to act as a cathode
Implementation Method 3
calculating the current and potential distribution in the soil
Data Source
AI summary
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.