Half-Cell Potential Test
(Corrosion Probability Test)

Non-destructive electrochemical test to assess the probability of active corrosion of reinforcing steel in concrete — the most widely used first-level corrosion screening method for RCC structures.

Overview

What is the Half-Cell Potential Test?

The Half-Cell Potential Test measures the electrochemical potential of embedded reinforcing steel relative to a standard copper/copper sulphate half-cell reference electrode placed on the concrete surface. The measured potential indicates the probability of active corrosion occurring in the rebar at that location.

Conducted as per ASTM C876, half-cell potential surveys are the standard first-step corrosion assessment for bridges, parking structures, marine buildings and any RCC structure in a chloride or carbonation environment. Global Lab uses calibrated half-cell equipment with data loggers for mapped potential surveys over large areas.

Corrosion Probability Mapping

Grid-based survey produces colour-coded potential maps showing high-risk zones.

ASTM C876 Classification

Potential values classify areas as >90%, 50% or <10% probability of corrosion.

Large Area Coverage

Rapid scanning covers entire bridge decks, parking floors or building facades.

Non-Destructive

Copper/copper sulphate electrode on wetted surface — zero damage to structure.

NABL Certified Reports

All results on NABL-accredited letterhead with colour potential contour maps.

Combined Corrosion Package

Paired with Galva Pulse and resistivity for complete quantitative corrosion audit.

Test in Action

Half-Cell Potential Test — Site Images

Half-Cell Electrode on Concrete Surface

Grid-Based Potential Survey in Progress

Colour Potential Map Generated

Test Procedure

How the Half-Cell Potential Test is Conducted

1

Surface Wetting

Concrete surface is wetted with water or wetting agent to ensure electrical continuity between surface and rebar.
2

Electrical Connection to Rebar

A wire connection is made to the reinforcing steel by drilling a small hole or using an existing connection point.
3

Half-Cell Electrode Placement

Copper/copper sulphate half-cell electrode is placed on the wetted concrete surface at grid points (typically 200×200mm spacing).
4

Potential Measurement & Logging

The potential difference between the half-cell and rebar is measured by a high-impedance voltmeter and logged automatically.
5

Potential Map & Risk Assessment

Measured potentials are plotted as a colour-coded contour map. Zones are classified per ASTM C876 Table 1. NABL report with map issued within 24 hours.

Standards & Specifications

Applicable Test Standards

Standard	Title	Scope	Type
ASTM C876	Standard Test Method for Corrosion Potentials of Uncoated Reinforcing Steel in Concrete	Half-Cell Potential	ASTM
BS 1881-204	Testing Concrete — Recommendations for Use of Electromagnetic-Covermeters	Rebar Detection	British Standard
RILEM TC 154-EMC	Half-Cell Potential Measurements — Potential Mapping on Reinforced Concrete Structures	Corrosion Assessment	RILEM
IS 13311	Non-Destructive Testing of Concrete — Recommendations	General NDT	Indian Standard

Applications

Where is the CAPO Test Used?

Bridges and flyovers in marine or de-icing salt environments

Multi-storey parking structures exposed to vehicle-tracked chlorides

Coastal residential and commercial buildings showing rebar corrosion staining

Pre-repair assessment to identify high-risk zones for targeted treatment

Post-repair monitoring to verify effectiveness of cathodic protection or coating

Industrial structures exposed to chloride-bearing process water or vapours

Why Choose Global Lab

Our Advantages

NABL Accredited ReportsLegally valid corrosion assessment certificates for all government and insurance requirements.

Colour Potential MapsDetailed contour maps identify high-risk zones for targeted repair budgeting.

Combined Corrosion AuditHalf-Cell + Galva Pulse + Resistivity + Carbonation as a complete package.

Large Area CoverageEfficient grid scanning covers bridge decks and parking floors rapidly.

Pan-India CoverageField engineers across 7 lab locations for rapid site deployment.

Fast TurnaroundOn-site results immediately; formal NABL report within 24 hours.

Half-Cell Potential Test(Corrosion Probability Test)