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Would the Real – 850mVcse Potential Criterion Please Stand Up

Published: 20120311 by NACE International
Author(s): Robert Gummow
Co-Author(s): Wolfgang Fieltsch - Corrosion Service, Sorin Segall - Corrosion Service

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 Impy 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.