Comments from Roy Bash

Richard:



It seems that the committee’s agenda is to word 6.2.3.1.1 in such a way that the only negative 850 Mv cp criterion that will be acceptable to the regulation agencies’ representatives will be the instant-off measurement.

The committee writes that the negative 850 Mv polarized cp criterion may be measured direct. As R.A. gummow ,a member of the committee, explains in his article,” Cathodic Protection Potential Criterion For Underground Steel
Structures”,MP/November,1993 ,Page26, this can only be done by placing the CSE at the structure/electrolyte –interface or using a capillary bridge to measure the polarized potential while the cp current is being applied. The following is quoted from Mr. gummow’s article.

“to determine whether a structure is protected with respect to a potential criterion such as -0.850V,CSE, the reference electrode must either be placed directly at the structure-electrolyte interface or be electrolytically connected to the structure-electrolyte interface by a capillary bridge to determine the polarized potential while the CP current is being applied.”

It has always been accepted that the polarized potential must be measured while the CP current is being applied as Mr. Gummow makes clear in the above quotation.

The instant-off potential can never be the same as the polarized potential. The two potential measurements are close in brine water or similar highly conductive electrolytes, but in natural soils and waters they will never be close. The polarized potential will always be several to many more MV than the instant-off potential.

Respectfully Submitted,

L.A.(Roy)Bash,P.E.