| 1. |
- Cassagne, Thierry B., et al.
(författare)
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Long term corrosion testing and monitoring of oxygen and corrosion potential in an umbilical design
- 2012
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Ingår i: NACE - International Corrosion Conference Series. - 9781622760787 ; , s. 1096-1108
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Konferensbidrag (refereegranskat)abstract
- Subsea umbilicals are used for control and operation of subsea oil and gas production facilities. Typically an umbilical consists of steel tubes, electrical cables, fiber optic cables, weight or strength elements and fillers. Super duplex stainless steel tube material has been used for almost 20 years within the umbilical industry. However, a recent failure on two orbital welds of 25Cr super duplex of an umbilical installed in the South China Sea was reported. From these results some umbilical end users recommended the use of thermoplastic coating to avoid crevice corrosion on 25Cr super duplex stainless steel above 20°C. However, this limit is based on results obtained for super duplex stainless steel in aerated natural seawater and very little is known on the micro-environment formed by the confined seawater between metallic tubes and polymer matrix of an umbilical. This work reports corrosion potential and oxygen content measurements in the confined zone between the metallic tubes and the polymer matrix of an umbilical. These measurements were performed using micro-electrodes on a 2 meter long real umbilical at 30°C in heated natural seawater. From the measurements, it is shown that the oxygen content in the confined zone is rapidly consumed probably due to the passive current on the stainless steel tubes and then remains below 2 ppm over one year exposure period. From the open-circuit potential measurements performed in the confined zone, it is clear that the open circuit potential remained below -150 mV/AgCl. This translates an absence of electrochemical effect of the biofilm in the confined zone. Visual and metallographic examinations of the tubes after exposure confirmed the results obtained by the microelectrodes and clearly indicate that no corrosion initiation occurred on superduplex stainless steel (base metal and welds) under these experimental conditions. The results are discussed in view of the validity of corrosion tests performed under aerated conditions and the need of further developments of new testing procedures to represent the confined situation in the umbilical design.
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| 2. |
- Abi Nassif, L., et al.
(författare)
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Reduction of potential ennoblement of stainless steel in natural seawater by an ecofriendly biopolymer
- 2020
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Ingår i: Journal of Environmental Chemical Engineering. - : Elsevier Ltd. - 2213-3437. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- The effect of biofilm formation on passive stainless steel in seawater environments is of primary importance since it leads to potential ennoblement of surfaces and subsequently to localized corrosion such as pitting and crevice corrosion. This study aims at developing an ecofriendly alginate biopolymer containing both non-toxic calcium and a limited amount of biocidal zinc ions which inhibits this effect. For this purpose, calcium alginate containing less than 1 % of zinc ions localized in the vicinity of the steel surface in natural and renewed seawater is demonstrated to reduce significantly the ennoblement process of steel. After 1 month of immersion, a mass loss of only 4 % of the active material is observed authorizing thereby long-term protection of steel in real environment.
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| 3. |
- Becker, Johan, et al.
(författare)
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Atmospheric corrosion of silver, copper and nickel exposed to hydrogen sulphide : a multi-analytical investigation approach
- 2022
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Ingår i: Corrosion Science. - : Elsevier Ltd. - 0010-938X .- 1879-0496. ; 209
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Tidskriftsartikel (refereegranskat)abstract
- The effect of two concentrations of H2S (0.5 and 2.5 ppm), in controlled laboratory conditions (20 °C, 75%RH), on the atmospheric corrosion of pure Ag, Cu and Ni was investigated in this study. The corrosion product morphology and composition were analysed through a multi-technique approach including SEM/EDX, Raman spectroscopy, XPS and XRD. Different corrosion products were identified depending on the type of characterisations providing a better overview of the effect of H2S on the atmospheric corrosion of pure Ag, Cu and Ni. Possible mechanisms involved in the formation of these corrosion products are also discussed in this work. © 2022 The Authors
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| 4. |
- Diler, Erwan, et al.
(författare)
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Characterization of corrosion products of Zn and Zn-Mg-Al coated steel in a marine atmosphere
- 2014
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Ingår i: Corrosion Science. - : Elsevier Ltd. - 0010-938X .- 1879-0496. ; 87, s. 111-117
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Tidskriftsartikel (refereegranskat)abstract
- The corrosion behaviour of pure zinc and zinc-magnesium-aluminium alloy (ZMA) has been studied during 6months of exposure in marine environment (Brest, France). The composition of corrosion products is analysed using infrared spectroscopy (FTIR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). An improved corrosion resistance of ZMA is observed. This improvement is found to be connected to Mg2+ and Al3+ induced quenching of corrosion activity and to the enhancement of NaZn4Cl(OH)6SO4·6H2O in the formed corrosion product.
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| 5. |
- Diler, Erwan, et al.
(författare)
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Chemistry of corrosion products of Zn and MgZn pure phases under atmospheric conditions
- 2012
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Ingår i: Corrosion Science. - : Elsevier BV. - 0010-938X .- 1879-0496. ; 65, s. 178-186
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Tidskriftsartikel (refereegranskat)abstract
- We present a corrosion behaviour study of pure phases of zinc and zinc-magnesium contaminated with NaCl and exposed to humid air for 30days: Zn, Mg 2Zn 11 and MgZn 2. The composition of corrosion products is analysed using infrared spectroscopy (FTIR), X-ray diffraction (XRD), ion chromatography (IC), and X-ray photoelectron spectroscopy (XPS). The improved corrosion stability of MgZn 2 is found to be connected to changes in the surface pH and to the nature of the formed corrosion products. The presence of magnesium modifies the proportion of the OH and CO 3 bonds in the corroded products. This explains the improvement in corrosion resistance.
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| 6. |
- Diler, Erwan, et al.
(författare)
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Initial formation of corrosion products on pure zinc and MgZn2 examinated by XPS
- 2014
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Ingår i: Corrosion Science. - : Elsevier BV. - 0010-938X .- 1879-0496. ; 79, s. 83-88
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Tidskriftsartikel (refereegranskat)abstract
- A corrosion behaviour study of pure phases of zinc and zinc-magnesium (MgZn2) exposed to humid air at 35°C for 4days is presented. For zinc, hydroxide formation at the surface and zinc oxide in the first innerlayers is observed. The corrosion of the MgZn2 leads to the segregation of magnesium at the surface to mainly form magnesium hydroxycarbonate: the presence of magnesium modifies the corrosion products. At larger depths, metallic zinc coexists with magnesium oxide and hydrozincite. The higher reactivity of MgZn2 alloy can be attributed to the interaction with carbonate ions.
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| 7. |
- Diler, Erwan, et al.
(författare)
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Stability of ZnMgO oxide in a weak alkaline solution
- 2012
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 520:7, s. 2819-2823
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Tidskriftsartikel (refereegranskat)abstract
- Zinc oxide (ZnO) is a chemical compound of great interest used, for example, as photocatalyst in the purification of wastewater or polluted air. However, neither dissolution, nor photo-dissolution of ZnO is negligible: indeed, both processes reduce significantly the efficiency of photocatalysis and then lead to a secondary pollution by free Zn 2 +. In the present study, the stability of ZnMgO thin films in weak alkaline solution is investigated. We demonstrate that the replacement of Zn 2 + ion with Mg 2 + ion results in the production of a Zn 0.84Mg 0.16O solid solution, whose stability is higher than that of the ZnO sample. This alloy, thus, constitutes an alternative to the use of ZnO in photocatalysis applications. To gain more insights into the higher resistance of such alloys to the dissolution process, X-Ray photoelectron spectroscopy measurements were performed. They highlighted the role of OH group adsorption in the experimentally observed enhancement of ZnMgO stability.
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| 8. |
- El Masri, I., et al.
(författare)
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Development of a RFID sensitive tag dedicated to the monitoring of the environmental corrosiveness for indoor applications
- 2020
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier B.V.. - 0925-4005 .- 1873-3077. ; 322
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Tidskriftsartikel (refereegranskat)abstract
- The environmental corrosiveness is governed for indoor applications by the presence of gaseous pollutants in air and levels of temperature and relative humidity. Its determination is a challenging task and requires the monitoring of thickness reduction of selected metals in the range of few tens of nanometers. The present work aims at developing an UHF RFID (Ultra High Frequency Radio Frequency Identification) sensor dedicated to such measurements. The sensor is based on the coupling between the antenna of a commercial RFID tag and a thin layer of copper exposed to the environment. The ability of the proposed sensor to be sensitive to a variation of the metal thickness in the range of tens of nanometers is demonstrated experimentally through exposure tests in a climatic chamber. The results are supported by electromagnetic simulations performed in the case of a coupling between a dipolar antenna and a thin metallic layer.
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| 9. |
- Larché, Nicolas, et al.
(författare)
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Effect of service conditions on the corrosion of nickel-aluminum bronze and copper-nickels alloys in seawater
- 2019
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Ingår i: NACE - International Corrosion Conference SeriesVolume 2019-March, 2019, Article number 13337Corrosion Conference and Expo 2019; Nashville; United States; 24 March 2019 through 28 March 2019. - : National Assoc. of Corrosion Engineers International.
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Konferensbidrag (refereegranskat)abstract
- Nickel-Aluminum Bronze (NAB) and Copper-Nickel alloys (CuNi) are commonly used in seawater environments due to their strength combined with a good corrosion resistance and a high resistance to biofouling. However, localized corrosion failures have been reported and are often attributed to abnormal service conditions. The effect of several service condition parameters on the localized corrosion of NAB (UNS C63000, CuAl10Ni5Fe4) and CuNi alloys 90/10 (UNS C70600) and 70/30 (UNS C71500) have been investigated in natural seawater. The results are compared with that of Aluminum-brass (UNS C68700). It includes flow conditions (flowing, quiescent and stagnant), chlorination, sulphide pollution, and crevice geometries. Exposures in both indoor (laboratory) and outdoor tanks (conditions promoting macro fouling) have been tested in temperate and in tropical seawaters. The corrosion stability of the protective oxide layer of the tested copper-based alloys was mainly affected by sulphide pollution in aerated seawater (general corrosion). Under the tested conditions, localized corrosion under-biodeposit clearly appeared as the critical failure for the tested alloys. The conditions for which biodeposit appeared critical for copper-nickel alloys was investigated.
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| 10. |
- LeBozec, Nathalie, et al.
(författare)
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Effect of climatic parameters on filiform corrosion of coated aluminium alloys AA6016
- 2003
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Ingår i: NACE - International Corrosion Conference Series. - : National Association of Corrosion Engineers International.
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Konferensbidrag (refereegranskat)abstract
- The effects of temperature, relative humidity and wet dry transition on initiation and propagation of filiform corrosion on coated aluminium alloys AA6016 have been studied. The aluminium surfaces were tested in both milled and grinded conditions with chromium, phosphate and titanium-zirconium based pretreatment. A full paint system used for automotive applications (ED coat + top-coat) and an electrodeposited coat (ED coat) were investigated for the different combinations of mechanical finish, surface pretreatment and coating system. In the temperature range between 5 to 50°C, filiform corrosion, or underfilm corrosion in general, increased significantly. The effect of relative humidity and wet-dry cycling on the other hand, seems to be strongly influenced by parameters like pretreatment, coating system, and also temperature. Filiform corrosion was the highest in the range 75 to 95 % relative humidity and a distinct maximum was observed at 85% R.H. for some coating systems. However, filiform corrosion propagated at humidity down to 40-50% R.H. For specimens with chromate and phosphate based surface pretreatments, filiform corrosion was lower after exposure to tests with wet-dry cycles. The samples with titanium-zirconium based pretreatments, on the other hand, had a very poor filiform corrosion resistance in the cyclic test compared to exposures at constant relative humidity. © 2003 by NACE International.
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