Monday, February 8, 2010

Comments from Aynonomus

I totally agree with you and I feel that 0.850 V "ON" criteria has proven to be good enough for many years...

But if they refuse to accept the 0.850 V "ON" criteria anymore for whatever reason, has anyone thought about just increasing the ON potential up to maybe 0.950 or even 1.000 V "ON" to add additional protection yet not requiring as much additional labor/expense?

This might be an acceptable option or also worth evaluating...

Comments from Paul Nichols


Of course you know there is nothing to prevent someone from using -850 mV On now, if the data is available to support that it is effective. SP0169 permits it, it just takes a bit of work, like collecting the data you ask for in your note. A combination of operator data on soil, coating and CP conditions, some ECDA and/or ILI data, plus the previous PRCI study would be sufficient to show if -850 On is effective. I think the same sort of, or substantially similar, data would be required anyway even in a revised SP0169; some data to show that the conditions are appropriate for -850 On and to show that it works.



Paul Nichols

Senior Materials and Corrosion Engineer; Mechanical, Materials and Integrity - East

Projects and Engineering Services

Shell Projects and Technology

Sunday, February 7, 2010

Message from Jim Chmilar

Richard: I would like to thank you for your contribution in submitting comments for the STG 35 Ballot last August in the review of the TG 360 revision of SP0169-2007. I know you are aware that the ballot did not get the 2/3rd affirmative vote necessary to proceed and the document was sent back to the task group for revision. I believe that your comments along with the others have now been reviewed and discussed and revisions have been made during at least one of the SIX web-conference call meetings held by the task group members since CTW 2009 (in addition to many e-mail exchanges).

The task group is down to making the final revisions and we will hopefully be out for a four week ballot period during February with a ballot close before San Antonio so we can be discussing ballots results at the Tuesday March 16, 2010 TG 360 meeting.

I trust you will find your comments and views have been addressed in the ballot draft when it comes out. Be assured that if you have any comments or concerns about the document that your negative or affirmative vote will be addressed during Corrosion 2010 or following meeting(s) if necessary. Please consider that if you do submit a negative vote that you must provide a suggested resolution that can be printed in the document, a number of negative voters did not do this last time.

Thank you for your contribution to technical committee activities

Jim Chmilar

Comments from Jim Jenkins


In addition to all of your comments, most of which I agree with, any potential measurement using a reference electrode where the absolute potential is to be determined needs to include the temperature of the reference electrode at the time of measurement. This is a bigger problem for the Cu/CuSO, than for the Ag/AgCl reference, but is a problem for both. In fact, I actually made the statement at an early RP-0169 revision meeting that "any absolute potential reading using a reference electrode where the temperature of the reference electrode is unknown is meaningless". I don't even think that using a reference electrode for potential rise or decay is valid unless the temperature of the reference electrode is known, or known not to change significantly during the measurement.

I hate zinc reference electrodes as I have found that the potential of even a freshly polished zinc reference can vary on soil by over 200 mV. It is closer for a freshly polished zinc reference in seawater ( about -1.05 V vs Ag/AgCl ) but the main problem in seawater is that the zinc always becomes more electropositive which indicates a more protected potential than would be measured when using a real reference electrode such as an Ag/AgCl. I am currently working on a project where using a zinc reference (even after I warned the owner that this is not satisfactory) to monitor a C.P. system has resulted in several millions of dollars of damage to a marine structure. Why risk structural integrity to save $ 100.00 on a reference electrode?

I plan to remain a voice in the wilderness on this and will continue to vote negative on SP-0169 until this is included. I have given my comments to NACE previously on this with my negative vote with no success.

Jim Jenkins