Basic Half-Cell System for Detecting Areas of Probable Rebar Corrosion
The James Cor-Map® System is a simple, reliable, and cost-effective half-cell potential testing system designed to identify areas of probable reinforcing steel (rebar) corrosion in concrete structures. Compliant with ASTM C876, the Cor-Map® enables engineers, consultants, and asset owners to quickly assess corrosion activity and prioritise maintenance before significant structural damage occurs.
Purchasing Notes
- For comprehensive corrosion analysis, use in conjunction with the James R-C-400 Rebarscope®.
- Consumable required: C-CM-4210 Copper Sulphate Solution.
Applications
The Cor-Map® System is ideal for evaluating corrosion activity in reinforced concrete structures, including:
- Bridge decks
- Parking structures
- Concrete piers and marine structures
- Building substructures
- Tunnel linings
- Foundations
- Civil infrastructure inspections
Features & Benefits
- Complies with ASTM C876 half-cell potential testing
- Simple and economical corrosion assessment method
- High-impedance digital voltmeter for accurate field measurements
- Durable construction for demanding site conditions
- Detachable electrode extension pieces for difficult-to-access locations
- Reference electrode suitable for horizontal, vertical and overhead testing
- Fast identification of probable corrosion areas
- Portable and easy to operate
Product Information
The James Cor-Map® System measures the half-cell potential between embedded reinforcing steel and a copper/copper sulphate reference electrode placed on the concrete surface. These measurements indicate the probability of active corrosion occurring within the reinforcing steel.
By taking measurements at regular intervals across a concrete surface, users can quickly create a grid of half-cell potentials. The resulting data can then be plotted to produce contour maps that highlight areas with an increased likelihood of corrosion activity, allowing targeted inspection, repair and rehabilitation.
The Cor-Map® System offers a practical, non-destructive solution for evaluating the condition of reinforced concrete infrastructure and planning preventative maintenance programs.
How Half-Cell Potential Testing Works
Steel reinforcement corrodes when moisture and oxygen penetrate the concrete and initiate an electrochemical reaction. The Cor-Map® System measures the electrical potential difference between the reinforcing steel and a stable copper/copper sulphate reference electrode.
The measured voltage does not indicate the amount of corrosion present, but instead provides the probability that active corrosion is occurring near the measurement location.
Testing is performed over a predetermined grid, allowing engineers to generate corrosion potential maps that identify areas requiring further investigation or repair.
Interpreting ASTM C876 Results
Using a Copper/Copper Sulphate (Cu/CuSO₄) reference electrode:
| Half-Cell Potential | Probability of Active Corrosion |
|---|---|
| Greater than 350 mV | Approximately 95% probability |
| 200–350 mV | Approximately 50% probability |
| Less than 200 mV | Approximately 5% probability |
Typical Applications
The Cor-Map® System is particularly well suited for:
- Bridge deck inspections
- Parking garages
- Concrete wharves and docks
- Marine structures
- Building foundations
- Tunnel linings
- Asset condition assessments
- Concrete rehabilitation projects
System Components
| Model | Description |
| C-CM-4500 | High-impedance digital voltmeter |
| C-CM-4410 | Electrode extension pieces (18 in / 41 cm each) |
| C-CM-4400 | Copper/copper sulphate reference electrode with reservoir |
| C-CM-4210 | Copper sulphate container (250 ml) |
| C-CM-4220 | Wetting agent reservoir (125 ml) |
| C-CM-4420 | Dispensing sponge |
| C-CM-4300 | Cable reel with 250 ft (80 m) cable |
| C-CM-4000 | Complete Cor-Map® System |
Standards
- ASTM C876 – Standard Test Method for Corrosion Potentials of Uncoated Reinforcing Steel in Concrete