ASTM
ASTM C876
Standard Test Method for Corrosion Potentials of Uncoated Reinforcing Steel in Concrete
The half-cell potential test, the standard non-destructive method for assessing whether reinforcement in a concrete structure is corroding. A copper–copper sulphate reference electrode is placed on the wetted surface and referenced to exposed rebar, and the measured potential is mapped across the element. Readings more negative than −350 mV indicate a greater than 90% probability of corrosion; readings less negative than −200 mV, a greater than 90% probability of no corrosion. The standard is explicit that the result is a probability of activity — not a rate, and not a measure of section loss.
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