Electrolyte-Immersed Metal Assessment for IR-Free Potential
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Solution Overview
Problem
Existing methods for assessing the effectiveness of cathodic protection on metallic structures in contact with electrolytes, such as soil or water, are cumbersome and inaccurate due to voltage drops and the inability to determine IR-free potential, especially for small coating defects, making it difficult to ensure effective corrosion protection.
Innovation Solution
A method and system that utilize both direct current (DC) and alternating current (AC) within the structure to measure DC voltage and AC voltage, allowing for the determination of DC potential and AC potential, which enables the localization of coating defects and assessment of cathodic protection effectiveness without the need for long cables, using electromagnetic field sensors to determine current flows and resistivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Intensive Measurement (IM) method is used to determine IR-free potential, then measurement accuracy is improved, but device complexity and installation requirements worsen due to need for long cables and fixed test posts
Solution Approach 1:
The patent replaces the mechanical cable-based measurement system with an electromagnetic field-based system. Electromagnetic field sensors measure the magnetic field generated by current flow in the structure, eliminating the need for physical cable connections to distant test posts. This substitution maintains measurement capability while removing installation complexity.
Solution Approach 2:
The patent introduces electromagnetic field sensors as intermediaries between the structure and the measurement system. These sensors detect the magnetic field indirectly generated by current flow, serving as a mediator that allows measurement without direct electrical connection through long cables.
2Measurement precision
If protective current is increased to improve measurement resolution, then measurement sensitivity is improved, but cathodic protection level changes which alters the IR-free potential
Solution Approach 1:
The patent applies alternating current (AC) in addition to direct current (DC) to the structure. The AC component allows for measurement of voltage gradients and determination of IR-free potential without requiring large changes in the protective DC current level. This periodic action enables sensitive measurements while maintaining stable cathodic protection conditions.
Solution Approach 2:
The patent changes the measurement approach from directly measuring potential at test posts to measuring voltage gradients along the structure. By measuring the gradient and using mathematical relationships, the system can determine IR-free potential without needing to increase protective current levels, thus maintaining measurement resolution while preserving protection stability.
3Measurement precision
If off-potential measurement is used to avoid voltage drops, then measurement accuracy is improved for single defects, but reliability worsens for multiple defects with different IR-free potentials
Solution Approach 1:
The patent divides the structure into multiple measurement sections with electrodes placed at different locations. By measuring voltage gradients across multiple segments and analyzing the current distribution, the system can determine IR-free potentials for individual defects even when multiple defects with different potentials are present, providing reliable multi-defect assessment.
Solution Approach 2:
The patent uses the measured voltage gradient data to calculate and provide feedback on the current distribution and defect locations. This feedback loop enables the system to iteratively determine accurate IR-free potentials for multiple defects by analyzing how current divides at different defect locations, improving reliability for multi-defect scenarios.
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
Enables accurate and efficient localization of coating defects and assessment of cathodic protection effectiveness, reducing the need for extensive cable installations and providing reliable corrosion protection.
Implementation Method 1
providing, at least within the structure, a direct current (DC) and an alternating current (AC) via the electric source
Implementation Method 2
using electromagnetic field sensors to determine current flows and resistivity
Implementation Method 3
measuring a direct voltage (DC voltage) UDC and an alternating voltage (AC voltage) UAC between a first electrode and a second electrode
Data Source
AI summary
A method for assessing a structure arranged in an electrolyte includes connecting an electric source between the structure and a low resistive connection to the electrolyte via an earth, providing a direct and/or alternating current via the source, measuring a direct and an alternating voltage between a first and second electrode, the electrodes being in contact with the electrolyte at a measurement location and being arranged at a distance to each other. The first and second electrodes are connected to a voltage measurement device. A direct potential and an alternating potential is determined between the structure and the electrolyte at the measurement location, which may include measuring the DC potential and the AC potential between the structure and at least one additional electrode in contact with the electrolyte. A property of the structure may be assessed based on the measured DC and AC voltages, and the DC and AC potentials.