Ferromagnetic Layer Corrosion Detection Through Magnetic Field Mapping

Resolve Bottlenecks,
Find Innovative Solutions
Generate Solutions

Solution Overview

Problem

Existing methods for detecting corrosion in metal reinforcements embedded in structures like reinforced concrete are costly, require direct access, are prone to measurement errors due to environmental factors, and lack effective preventive maintenance capabilities.

Innovation Solution

A method involving the measurement and comparison of magnetic characteristic values of permanent magnets attached to ferromagnetic layers, using a three-dimensional reference frame to estimate corrosion by comparing acquired magnetic field data, and employing a calibration curve to deduce corrosion and pathogen infiltration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If core sampling tests are used to determine chloride ion concentration, then corrosion progress can be estimated, but the method is destructive and limits sampling across the entire structure

Engineering Contradiction:
Improvecorrosion progress estimationVSAvoidsampling representativeness
Core Design Contradiction:
Measurement precisionVSReliability

Solution Approach 1:

The patent uses magnetic sensors to create a non-destructive copy of the corrosion state by measuring magnetic field variations caused by chloride ion concentration and reinforcement corrosion. This replaces destructive core sampling with a magnetic field-based measurement system that can assess the entire structure without physical removal of material.

Inventive Principle:
Principle #26Copying

Solution Approach 2:

The patent replaces the mechanical core sampling process with a magnetic field-based measurement system. Magnetic sensors detect changes in magnetic properties caused by corrosion and chloride infiltration, substituting physical material removal with field-based detection that preserves the structure integrity.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Ease of operation

If electromagnetic radar is used for corrosion detection, then non-contact measurement is achieved, but measurement results are sensitive to environmental factors such as humidity and chloride levels

Engineering Contradiction:
Improvenon-contact measurementVSAvoidmeasurement accuracy
Core Design Contradiction:
Ease of operationVSMeasurement precision

Solution Approach 1:

The patent introduces magnetic sensors as an intermediary between the electromagnetic field and the corrosion targets. These sensors detect magnetic field variations caused by corrosion, providing a measurement mechanism that is less sensitive to environmental factors like humidity and chloride levels compared to direct electromagnetic radar measurement.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the measurement parameter from direct electromagnetic wave reflection to magnetic field property variations. By measuring changes in magnetic permeability and conductivity associated with corrosion, the system achieves more stable measurements that are less affected by environmental conditions.

Inventive Principle:
Principle #35Parameter changes

3Duration of action of stationary object

If integrated monitoring techniques with sensors are implemented, then long-term corrosion monitoring is achieved, but the cost and device complexity increase significantly

Engineering Contradiction:
Improvemonitoring durationVSAvoidsensor system complexity
Core Design Contradiction:
Duration of action of stationary objectVSDevice complexity

Solution Approach 1:

The patent employs magnetic sensors that serve multiple functions: detecting chloride ion concentration, monitoring reinforcement corrosion, and assessing coating degradation. This multi-functionality reduces the need for multiple specialized sensors, thereby lowering overall system complexity while maintaining long-term monitoring capability.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent monitors temporal changes in magnetic field parameters to detect corrosion progression over time. By tracking variations in magnetic permeability and field strength, the system achieves long-term monitoring through simple, repeatable measurements that do not require complex sensor configurations.

Inventive Principle:
Principle #35Parameter changes

4Ease of operation

If visual inspections are used to identify cracks, then surface defects can be detected, but the method cannot assess internal corrosion of embedded reinforcement

Engineering Contradiction:
Improvesurface defect detectionVSAvoidinternal corrosion detection
Core Design Contradiction:
Ease of operationVSDifficulty of detecting and measuring

Solution Approach 1:

The patent replaces visual inspection with magnetic field-based detection that can penetrate concrete and sense internal reinforcement conditions. Magnetic sensors detect changes in magnetic properties caused by corrosion of embedded steel, providing information about internal conditions that visual inspection cannot access.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent uses magnetic field lines as an intermediary to probe internal reinforcement conditions. The magnetic field penetrates the concrete coating and interacts with the embedded steel reinforcement, allowing detection of corrosion state without direct visual access to the internal components.

Inventive Principle:
Principle #24Intermediary (Mediator)

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, non-destructive corrosion detection and preventive maintenance by reducing measurement errors and environmental interference, allowing for timely maintenance to extend the lifespan of infrastructure.

Implementation Method 1

measuring a value of a magnetic characteristic (B) by means of the measuring device at the location determined in the determination step

Methodology Applied
Scientific EffectMagnetic field interaction: Magnetic Field

Implementation Method 2

detecting corrosion of a ferromagnetic corrodible layer comprising... measuring a value of a magnetic characteristic... of a magnet

Methodology Applied
Scientific EffectFerromagnetism: Ferromagnetism

Data Source

PatentEP4224142B1Method for corrosion detection and infiltration evaluation by measuring value of magnetic characteristic
Publication Date: 2025.09.24 CEREMA
  • EP4224142B1 patent drawingFigure 1
  • EP4224142B1 patent drawingFigure 2
  • EP4224142B1 patent drawingFigure 3

AI summary

One aspect of the invention relates to a method for detecting corrosion of a corrodible ferromagnetic layer (100) comprising: a step (E1) of acquiring data from different locations (Em10, Em11, Em12) of at least one magnet (10, 11, 12), of the magnetic characteristic value for each magnet (10, 11, 12); a step of determining a location (Ea210, Ea211, Ea212) of a measuring device (20); a step of measuring and recording (E3) a magnetic flux density (B) at the location (Ea210, Ea211, Ea212); a step of estimating (E4) by the processor (21) a magnetic characteristic value of at least one magnet (10, 11, 12) as a function of the measured magnetic flux density (B); a step of comparing the estimated magnetic characteristic value and that previously estimated or acquired, a deduction step (E6) of corrosion of the corrodable layer (100, 110,120) depending on the comparison made in the comparison step (E5).