Pipeline Corrosion Control Voltage Measurements

PWP - 404 Error

This Page Cannot Be Found

Finally went to the net to find you.

I'm not sure what you want from this forum, except maybe a place to speak out against big business?

You seem to think there's some type of conspiracy going on among corrosion control companies?

Or, did I miss the point?

Not against anyone or any organisation ... just want to get real science into cathodic protection that is regarded by some as more of a craft.

Have you been here:

World Corrosion Organization

Or: Pipeline Corrosion Control - NCCER

Or: NACE International - The Corrosion Society

OR: ICORR Prevents Corrosion

Thanks for the links.

I was introduced into cathodic protection having spent seven years in pipeline construction and maintenance as an industrial safety officer. After this I qualified as an ERS coating inspector and was then offered a job as a Cathodic Protection Technician on a pipeline being constructed in the UK. I was given a multimeter and a copper rod in a plastic tube containing a saturated solution of copper sulphate, described to me as a 'half-cell'.

I was told to take a voltage between the half-cell and a brass stud on a CP test posts for the whole length of the pipeline that had been constructed so far.

I was told that the half-cell was the reference potential in the voltage and that I was recording the pipeline metal potential at each location.

However, when I moved the half-cell the voltage changed. The connection to the brass stud had not changed and I reasoned that the half-cell could not possibly be a stable reference when used in this way.

I was lent a copy of 'the bible of cathodic protection' Peabodies, published by NACE and studied it in detail while working. I found that a great deal of the advice simply did not work in the field, so I made the 'equivalent circuits', as shown in the book, out of electrical components, and they did not work either.

I wanted to find out the reality of this science and have been puting together a theory of how it all works for the past 30 years or more.

The coming of the internet has removed barriers and there are now a number of people who understand this engineering practice in the same way that I do. However, they are prevented from serving 'big business' by a small number of people who clearly do not understand electricity or applied cathodic protection.

The purpose of this topic is to allow the engineering world to examine the opinions of anyone caring join in.

Well, one thing's for sure. There is no shortage of opinions on this forum.

We do actually have some brilliant minds here. Maybe some of them will join in.

Corrosion is a pervasive problem that costs 3% or more of GDP for most developed nations.

Corrosion is a global problem that has plagued buildings, monuments, equipment, and infrastructure for centuries. Every day scientists, researchers, chemists, engineers, and other professionals create revolutionary solutions to combat corrosion and protect vital assets from the damaging effects of corrosion-related deterioration and failure. In working with folks in the military packaging industry, I know the importance of being pre-emptive when it comes to corrosion prevention or else you could wind up spending a lot more than you'd like. The time has come to tackle this issue head-on if we are to guarantee a long-term future for the oil and gas industry.

Than Nguyen

http://www.protectivepackaging.net/military-packaging

Regarding : "Papers presented at conferences and published by organisations involved with corrosion control refer to 'pipe-to-soil potentials' and to copper/copper-sulphate electrodes as reference electrodes" ...

Personally, I never cared for the simplified term ('pipe-to-soil potentials'), but it has gained acceptance and as such: "Live with it". You won't get hundreds of authors to rewrite text books etc simply to coin a new expression!

Peabody's IS a great reference, but it is only one ... of hundreds. Corrosion control IS a science, and it is very well matured. However, as materials change and evolve, and the environments to which new materials are subjected multiply and change, the science will continue to learn and grow.

I have a full 4-ft shelf devoted to 3" thick binders and books on the subject, and it took that much reading-and-absorbing to feel totally comfortable with the theory and application of corrosion-control. "Sure", when a probe ("half-cell") is moved, the reading changes. The (Test) "Corrosion-Cell" has changed! Variations occur between potential measurements taken by 2 different technicians the same as 2 ultrasonic test technicians will acquire different thickness measurements at the same test point.

THAT does not mean the science is bad. (I know, that went without saying.) Your post seems to indicate (to me, anyway) that you need "More_Input" in order to fully grasp WHY the science IS "where-it's-at" right now.

... and to: "an alternative to the monopoly who have dominated the commercial side of all corrosion control activities world wide" ...

? WHAT "monopoly"...?! Please provide a Wiki or Google link that names ANY entity as such.

... and to: "We require public debate on the validity of a process known as the measurement of the 'off potential' as this is one of the fundamental beliefs of present practices" ...

Again, it sounds as though you need "More_Input" in order to fully grasp the utter simplicity of this fundamental concept.

Go back to THE basics. Essentially, there are 4 mechanisms available for control of corrosion (with 'variations-on-each-theme') ... Isolation, Inhibitors, Cathodic Protection, and Environmental Control. YOU are addressing CP.

Upon what 'phenomenon' is CP based? (polarization) ... Ask yourself: "What is polarization?", and "to what extent do we polarize for corrosion-protection, and why?"

Certain elements WILL fall-into-place and make complete sense, but ONLY if you learn ALL of the different elements (preferably in the right order), and make the "connections" (I always LOVED those shows!)

Most certainly there exist structures (CP-protected) in environments where conditions warrent every imaginable level-of-concern, as well as warranting "extreme measures" as opposed to typical corrosion-control measures. Understanding THIS is where the job of the corrosion control technician becomes as much a "craft" (as you put it) or "Art Form" as it is a science.

Wishing you well as you progress in this career ~

Thank you for your very full response but I am in contact with working operatives, technicians, engineers and scientists and have been studying this matter for well over 30 years.

We need the technical appraisal of all corrosion control field practices by experts in electrical measurements as well as those engaged in scientific research and we need a criterion for cathodic protection to be agreed on an international level. I presented a paper on this matter at two major international conferences and recently offered another paper on the need for an international reference electrode based on position.

Despite there being national and international working groups on 'interference' the committee for that conference could not see the need for a potential that can be used to balance the electrical equilibrium of networks of pipelines, railways overhead power lines and other metalic conductive paths.

I am engaged in such work and have in the past investigated accelerated corrosion due to such disturbances as sun spots, teluric and geo-magnetic effects. Studies have been carried out by the Russians and the Germans and I was priviledged to be the field technician who ran the instruments in co-operation for a national UK pipeline organisation.

The understanding of exactly what we are measuring and the capability of each type of instrument is the key to removing many of the misunderstandings.

Having re-read your posts above, in the light of these additional comments, I am compelled to add what follows. You stated:

"I was told to take a voltage between the half-cell and a brass stud on a CP test posts ... (and) that the half-cell was the reference potential in the voltage and that I was recording the pipeline metal potential at each location. ... I wanted to find out the reality of this science and have been putting together a theory of how it all works for the past 30 years or more." ... "The understanding of exactly what we are measuring and the capability of each type of instrument is the key to removing many of the misunderstandings."

Clearly , you understand that there is FAR more to understanding corrosion issues than "Gran'pa's understanding": Y'see thet thar rust...that's the result of electroleesis (sic).

Sadly, THAT is the quality of response you might expect from ALL-TOO-MANY of those who peruse this forum. [Try searching CR4 for 'corrosion', and other related terms, and you will see what I mean.]

I should think that you would elicit MUCH more experienced/professional and thus technically complete and correct responses, by networking with those who participate in the (worldwide-&-free) NACE Corrosion Network. {Sign-up at the NACE website}

In response to your comments which I quoted above; the way it was explained to me (in one of my first classes w/NACE) is that whether you are testing buried pipeline ("pipe-to-soil") or submerged pipeline ("pipe-to-electrolyte"), you are actually measuring "the polarized potential of the structure with respect to a standard reference electrode*, in the (specified) electrolyte environment." However, THAT is simply the nutshell version. The talented technician (properly certified, so as to be engaged in CP_Surveys) understands the difference between "Activation Polarization" and "Concentration Polarization", as well as the multitudinous factors that might cause "Anomalous Measurements" (including telluric currents, stray currents, etc).

In spite of re-reading your postings thus far, I have yet to identify exactly what it is you hope to achieve. It most certainly can't be a "one potential fits all" solution, for the multitudinous / entangled networks that you described...

~

* ... and, for those who are NOT "in-the-know", there are DIFFERENT electrodes for use in measuring (corrosion) potentials in different environments. Seawater is NOT a good environment for the Copper/Copper-Sulfate half-cell ... (chloride ions migrating THRU the porous plug into the CuSO₄ solution will reduce the stability of the nobility of the copper rod, thus rendering it LESS stable). Thus, Silver/Silver-Chloride half-cells have been used more often than not for surveys performed in seawater.

A challenge to NACE, ICorr and all corrosion engineers. If the copper/copper-sulphate electrode is a reference potential how is there a difference between two of them in DCVG? If the copper/copper-sulphate electrode is a half-cell, what is the other half? We attach the meter to the section of pipe that has many corrosion cells. How do you interpret CIPS readings that are fluctuating? Do you know the nature of corrosion noise? Do you disagree with 'Gibbs Free Energy' that states that there can be no such thing as zero energy because free energy fills the void? (If there is no zero energy there cannot be a negative potential.) Why do NACE have a choice of three criteria to decide if corrosion has been stopped? Describe the measuring circuit when trying to decide the criterion and explain the scientific rational. Why can we not computers analyze CIPS survey results using the basic laws of electricity Ohms law and Kirchhoff's laws? (All we do is draw graphs and that is NOT analysis) Why are DCVG and CIPS not repeatable? The scientific method requires repeatable observable evidence. Explain how DCVG can show anodic and cathodic coating faults. It cannot, see DIN50918. Explain in detail how we measure ANY of the elements in ANY of the formulae that you teach.