Half-Cell Potential Mapping & Half Cell Surveys
Electrochemical Corrosion Probability Assessment
Overview
Half-cell potential mapping, also called a half-cell survey, is the standard electrochemical technique for assessing the probability of active reinforcement corrosion in concrete structures. SiteOps uses half-cell surveys to determine where corrosion is actively occurring, where it is not, and where conditions are transitioning toward corrosion onset.
A half-cell survey measures the electrical potential difference between embedded steel reinforcement and a reference electrode placed on the concrete surface. More negative readings indicate higher corrosion probability. ASTM C876 provides standard interpretation criteria for half-cell potential readings.
Half-cell surveys are used when visible spalling, cracking, or rust staining only tells part of the story, and an engineer needs to know how far corrosion activity actually extends before scoping repairs. This is common on car parks, balconies, marine structures, and any reinforced concrete with a history of chloride exposure or carbonation.
Half-cell mapping is performed on a systematic grid across the structure, producing contour maps that visualise the spatial distribution of corrosion probability. These maps are critical for proportionate remediation design - showing exactly where intervention is needed.
Half-cell surveys consistently demonstrate that the spatial extent of active corrosion is less than visual assessment alone would suggest, enabling targeted and cost-effective remediation.
Applications
Corrosion Probability Assessment
Systematic mapping of reinforcement corrosion probability to distinguish active from passive zones.
Remediation Scope Definition
Delineating actual extent of corrosion activity for proportionate remediation boundaries.
Condition Monitoring
Periodic surveys to track changes in corrosion state over time.
Post-Repair Verification
Verifying remediation has re-established passive conditions in treated zones.
Marine Infrastructure
Systematic corrosion assessment in marine and coastal environments.
Technical specifications
| Reference Electrode | Cu/CuSO₄ (CSE) |
|---|---|
| Grid | 300mm × 300mm (adjustable) |
| Active Corrosion | More negative than -350mV CSE (>90% probability) |
| Passive | Less negative than -200mV CSE (>90% probability) |
| Output | Contour maps of corrosion probability |
| Standards | ASTM C876, RILEM TC 154-EMC |
Related technologies
FAQ
Common questions
What is a half-cell survey?+
A half-cell survey measures the electrochemical potential of reinforcement at points across a grid to estimate the probability of active corrosion. It is a standard non-destructive technique for concrete affected by chloride exposure or carbonation, used to define repair extent rather than estimate it from surface condition alone.
What does half-cell potential measure?+
It measures the electrochemical potential between embedded steel and a reference electrode, reflecting the thermodynamic tendency of the steel to corrode.
When are half-cell surveys useful?+
Half-cell surveys are useful when visual defects do not show the full corrosion pattern. They help engineers decide where active corrosion is likely, where concrete repair should be targeted, and where chloride profiling or resistivity testing should be added.
Can it be used on all concrete?+
It requires electrical continuity with the reinforcement and sufficiently moist concrete. Very dry concrete may require modified techniques.
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