About this tool Classify the probability of reinforcement corrosion from half-cell potential measurements per ASTM C876-15. Enter the potential reading and select your reference electrode type — the tool converts to CSE equivalent and classifies the corrosion probability.
Three reference electrode types are supported: CSE (copper/copper sulfate), Ag/AgCl (silver/silver chloride), and SCE (saturated calomel). The tool applies the correct offset to convert all readings to the ASTM C876 CSE scale.
Half-cell potential mapping is the standard first-pass technique for identifying areas of active corrosion in reinforced concrete structures. Per ASTM C876-15.
How to use this tool 1. Select the reference electrode type — CSE is the ASTM C876 standard. Ag/AgCl and SCE readings are converted automatically.
2. Enter the potential reading in mV — typically a negative value. Enter as displayed on the instrument.
3. Read the corrosion probability — per the ASTM C876 three-category classification.
Technical information ASTM C876-15 thresholds (CSE): > −200 mV = >90% no corrosion; −200 to −350 mV = uncertain; < −350 mV = >90% active corrosion.
Electrode offsets: Ag/AgCl = CSE + 56 mV; SCE = CSE + 70 mV. Applied automatically when converting to CSE equivalent.
Limitations Half-cell potentials indicate corrosion probability at the time of measurement only. Readings are affected by concrete moisture, cover depth, temperature, and carbonation state.
The ASTM C876 thresholds are for bare (non-coated) reinforcement in chloride-contaminated or carbonated concrete. They may not apply to epoxy-coated bars, galvanised reinforcement, or cathodically protected structures.
Potential mapping should be interpreted as a pattern, not individual readings. Always consider the potential gradient across the structure, not just absolute values.
Revision history 11 August 2026: Initial release
Disclaimer This tool is provided for educational and general information purposes only. It is not a substitute for professional engineering advice, design or verification.
Diggy and its contributors are not licensed engineering consultants and no results generated by this tool should be used directly for construction, design or safety-critical decisions.
All values and outputs are based on published empirical correlations and should be independently checked and confirmed by a qualified geotechnical engineer before use.
By using this tool, you accept full responsibility for how you interpret and apply the information provided.
Spotted an error? Let us know .
