Materials Performance

SEP 2018

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

Issue link:

Contents of this Issue


Page 50 of 128

SEPTEMBER 2018 W W W.MATERIALSPERFORMANCE.COM W W W.MATERIALSPERFORMANCE.COM SEPTEMBER 2018 Installing anodes in frozen soil in 1966. Up to the 1960s, most anode bed installations in Canada were stopped in October when the ground first became frozen. Photo courtesy of Brian Holtsbaum. Canister anodes being filled in 1967. At the time, with limited lifting resources, the canisters were filled from a raised backhoe bucket and the sides of the canister were tapped to pack the coke inside. Photo courtesy of Brian Holtsbaum. Using Cathodic Protection to Protect Oil and Gas Pipelines from Corrosion Brian Holtsbaum Canada I believe the major innovation in this field was CP itself. Although the foundation for CP was laid by Sir Humphrey Davy and his understudy Michael Farady in the early 1800s, it took until the turn of the twentieth century before it was applied to a pipeline. Later in 1928, Robert J. Kuhn applied CP to a long-distance pipeline. Even as late as 1940 though, there was doubt as to the corrosion mechanism on pipe- lines and skepticism about CP. It became apparent of the need to form a group with a common concern for corrosion and its control. the leaks had essentially stopped. However, the leaks increased for a short time after CP was initially applied, which caused more skepticism. This was due to the corrosion product that plugged the through-wall pits in low-pressure pipelines being loosened with CP. The CP criterion has a long and troubled history—too long to discuss here. Briefly, Kuhn reported a final potential of –0.850 V vs. a copper/copper sulfate (Cu/CuSO 4 ) electrode (CSE). Apparently during the MCPA era, pipeline operators met to decide on a criterion by comparing their native potentials with a criterion being more electronegative. Marshall Parker (Pipeline Corrosion and Cathodic Protection author) advised me that the most electronegative native potential was –0.780 V vs. CSE, so an argument occurred as to whether the criterion should be –0.800 V vs. CSE or –0.850 V vs. CSE, with the latter finally being accepted. In 1969, NACE RP0169 (now SP0169-2013, "Control of External Corrosion on Underground or Submerged Metallic Piping Systems") was the first CP standard developed and the criterion was to be achieved with applied current. This criterion seemed to work, probably because 100 mV of polarization was coincidentally met. Eventually, corrosion leaks occurred at this criterion and many members of NACE started an investigation circa 1983. When it was proposed that the criterion should be a "polarized" instead of an "on" potential, there were extensive (often angry and emotional) discussions, but it was finally accepted in 1992. Part of the argument against the criterion change was that it was impractical to measure with the equipment at that time. The industry responded with Global Positioning System synchronized interruption, remote monitoring units with this feature, and datalog- gers. Now it is practical to measure not only a polarized potential, but it can be compared to a depolarized potential to assess the polarization criterion of 100 mV. There is still work to be done, but over the course of the last 75 years, CP has risen from a little-known orphan to a recognized major contributor in the control of corrosion—not only on pipelines but any buried or immersed structure. n W. Brian Holtsbaum, P.Eng., is president of Corsult Associates (1980) Ltd. (Calgary, Alberta, Canada). He has been involved in cor- rosion and CP since 1957 and specializes in submersed and under- ground structures in Canada and internationally. A NACE member for 60 years, Holtsbaum has been active in several NACE committees, has served on the NACE Board of Directors as NACE president (1995-96), and was a NACE CP instructor. He received the NACE Distinguished Service Award in 1986, the Distinguished Organization Award in 2002 with Associated Corrosion Consultants Ltd., and the Presiden- tial Achievement Award in 2017. He is the author of the NACE book, Cathodic Protection Survey Procedures, which was originally published in 2009 and has since been released in editions 2 and 3. Although NACE was officially formed 75 years ago, the seeds were planted in 1936 with the formation of the Mid-Continent Cathodic Protection Association (MCPA) that later joined with the America Petroleum Institute in 1939 as the CP Subcommittee. Reportedly little happened until 1940 when the CP Subcommittee was invited to become an affiliate of the Petroleum Industry Electric Association. This affiliation was eventually deemed unsatisfactory and 11 men saw the benefit in forming an independent association dedicated specifically to corrosion and its control; thus, NACE was formed in 1943. At that time, the end of World War II was still two years away. Canada's effort supported the key industries that, in turn, supported the war effort. It was difficult to sell a new concept such as CP that would take materials from the war, especially without total agree- ment on its benefit. When I first entered the CP field 14 years later, it was still a little-known technology and, in fact, was often misspelled as "catholic," giving the impression that it was black box religious wizardry designed to mystify people into believing that it prevented corrosion. Up to that point, only a few of the major pipeline com- panies in my area had installed it. There was little CP on upstream pipelines as the bare pipelines were expected to last until the oil well was depleted. Thus, the challenge was to prove that CP worked and was economically beneficial. An effective tool to demonstrate the worth of CP was a semi-log plot of leak frequency in an oil field. This curve unerringly showed a direct logarithmic increase in leaks after the first leak until several deep corrosion pits near each other were repaired and counted as one. The plot flattened to a degree, but the leak rate remained high. When CP was applied, the curve became almost flat, indicating A30 A30

Articles in this issue

Links on this page

Archives of this issue

view archives of Materials Performance - SEP 2018