Some recent papers contain inaccurate information regarding the validity of the -850 mVCSE current applied criterion, the so-called on-potential criterion. To qualify as a corrosion control criterion the -850 mVCSE value must imply a sound engineering judgment of the corrosion rate. Only the -850 mVCSE polarized potential criterion does this, as supported theoretically and empirically through its development, where a corrosion rate of less than 1mpy (< 0.025mm/a) is generally accepted. There is no similar scientific backing for the -850 mVCSE on-potential criterion. Numerous comparative studies of these two criteria illustrate that the corrosion rate can not be judged on the basis of an on-potential criterion when the IR drop is ignored. Failure to correct the on-potential measurement, by removing the IR drop, leaves the public exposed to an unnecessary safety risk.

Subject
Voltage drops, Piping, Cathodic protection, Corrosion rate, Cathodic potential, Pipelines, Soil resistivity, Corrosion protection, Polarized potential, Instant off potential, Soil, Corrosion potential, Electrode potential
Keywords:
-850 mVCSE potential criterion, polarized potential, on-potential, IR drop, corrosion rate, cathodic protection criteria
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2012
Association for Materials Protection and Performance (AMPP)
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