Friday, June 26, 2009

Voting process correction!

Richard I am a long time NACE member and am well versed in the controversy in RP0169 and have decided not to choose sides this time around. It is interesting to see how the draft is evolving. One comment though, I think your mistaken about how you need to vote on the first ballot to vote on subseqnent versions of the document. The RP0169 committee said in Atlanta that they send out a canvas first before they ballot and if you don't respond yes to the canvas then you don't get a vote on any ballots, and that's the way other NACE ballots work. If you vote yes on the canvas then you can vote on any of the ballots.

Monday, June 22, 2009

Comments from Bill Carlson

Richard, my only comment is that I have witnessed people that take readings and place the cell as close to the anode as possible and then record an ON potential in excess of the 850, and just feet away the potential is in the tank. How can we account for this type of behavior? This by the way is not an isolated case. In the real world, we would like to think that everyone does the best job in recording potentials and looking at the effect rather than just getting a reading that makes them and their boss happy. It was not that long ago when the corrosion engineer had to fight for every dollar so he could do a good job. I would not like to see that happen again, for one I am too old and the other is it is counterproductive. I do not have a strong opinion either way, but we should be realistic. I would rather error on more protection than marginal protection. Thanks for your time. Bill

William P. Carlson

Comments from Roy Bash


It seems that the committee’s agenda is to word 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,