Materials Performance

AUG 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.

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30 AUGUST 2018 W W W.MATERIALSPERFORMANCE.COM FEATURE ARTICLE The chart (left) shows the initial corrosion readings (after six days) from the ER corrosion sensors in two water depths at both berths at the Yamal LNG terminal, and in the laboratory. The graph (right) shows polarization data for Berth A before, during, and after icing. around them. The CP sensors were left on Berth A for 10 months during the icing and deicing seasons. The results confirmed that galvanic currents were almost null in ice (i.e., not measurable at <1 mA/m²). After deicing, the anodes from CP sensors reacti- vated and the polarization curve was simi- lar to the stabilized polarization curve before icing. This result indicates the icing period and low salinity did not passivate any of the tested anodes, and they were able to provide protective current again after deicing. Conclusions Without CP, the initial corrosion was higher in surface water than in water near the sea floor. This was attributed to the more agitated/turbulent conditions of sur- face water. In the solid ice phase, corrosion was very low, <10 μm/y. For both surface and sea floor waters, the mean CD to meet the CP criterion of –800 mV vs. SCE was similar to the mean CD recommended for seawater in the Arctic region, namely between 110 and 130 mA/m². The initial CD increased with the agitation (turbulent flow) to values between ~400 to 500 mA/m², but it significantly decreased after several days of exposure. In the test environment at Berth A, the zinc anodes never passivated, including anodes exposed at OCP. After the icing sea- son, the anodes reactivated and the polar- ization curve was similar to the stabilized polarization curve before icing. In solid ice, the galvanic anodes did not deliver signifi- cant current; however, the corrosion rates measured were almost null. The collected data for the Yamal LNG terminal facilitated an accurate CP design using actual polarization curves. Modeling should be used to evaluate the use of a gal- vanic anode system vs. an impressed cur- rent CP system. If a galvanic anode CP sys- tem is considered, magnesium anodes might be used in the surface water, with zinc anodes used at lower depths, since salinity on the surface water can be lower during the summer. Magnesium anodes would help to reach the initial high-current demand in very resistive water. References 1 D. Festy, et al., "ICP-DATA: In Situ Data Col- lection for Cathodic Protection Design," Journée PCRA (2011). 2 E. Diler, D. Thierry, D. Le Flour, "Cathodic Pro- tection of Duplex Stainless Steel for Deep Sea Application (ICP-DSS)," Institut de la Corro- sion, project no. 79092, 2015. 3 Seawater Tours: Treatments and Materials/ Union Chamber for Research and Production of Oil and Natural Gas, Technicians Committee (Paris, France: Technip, 1993). 4 F.L. LaQue, Marine Corrosion: Causes and Prevention (New York, NY: John Wiley, 1975), p. 104. 5 DNVGL-RP401, "Cathodic Protection Design" (Høvik, Norway: DNV GL, 2017). 6 ISO 15589-2:2012, "Petroleum, Petrochemical and Natural Gas Industries—Cathodic Pro- tection of Pipeline Transportation Systems— Part 2: Offshore Pipelines" (Geneva, Switzerland: ISO, 2012). This article is based on CORROSION 2018 paper no. 10933, "Field Cathodic Protection Study in the Specific Artic Conditions of the Yamal Gas Carrier Terminal," by N. Larché, J. Vittonato, E. Diler, and S. Shumovskiy. NICOLAS LARCHÉ is group manager, marine corrosion and cathodic protection with the Institut de la Corrosion, Brest, France, email: nicolas.larche@institut- corrosion.fr. He specializes in corrosion and anticorrosion of materials for sea water applications, including stainless steels, nickel-based alloys, and copper alloys. ERWAN DILER is a research engineer with the Institut de la Corrosion, email: erwan. diler@institut-corrosion.fr. He is the research and development leader for corrosion and cathodic protection in soils, aqueous media, and atmospheric condi- tions; and is experienced in corrosion sensors. JEAN VITTONATO is head of corrosion with Total E&P, Pau, France. He has been a NACE International member for 19 years. SERGEY SHUMOVSKIY is manager of the sea port design and construction depart- ment with Yamal LNG, Moscow, Russian Federation. He has been involved with the Yamal LNG project in the Arctic region since 2011.

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