Arradon, France
Arradon, France

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Refait P.,University of La Rochelle | Jeannin M.,University of La Rochelle | Sabot R.,University of La Rochelle | Antony H.,Corrodys | Pineau S.,Accoast SAS
Corrosion Science | Year: 2015

Carbon steel coupons were set in the tidal zone of a French seaport for 7years with or without cathodic protection. The average corrosion rates decreased from 90μmyr-1 to 9μmyr-1 under cathodic protection. The corrosion product layers covering the unprotected coupons, characterized by Raman spectroscopy and X-ray diffraction, were mainly made up of magnetite and Fe(III) oxyhydroxides, with magnetite being clearly predominant. The products of the residual corrosion process under cathodic protection, similar to those observed at open circuit potential, formed a thin layer on the steel surface under the calcareous deposit. © 2014 Elsevier Ltd.


Refait P.,University of La Rochelle | Pineau S.,Accoast SAS | Sabot R.,University of La Rochelle | Antony H.,BP 48 | Jeannin M.,University of La Rochelle
Materiaux et Techniques | Year: 2013

Carbon steel coupons were set in the tidal zone of two seaports (Le Havre and Nantes-Saint Nazaire). The layers of corrosion products covering the coupons after 6 months, 12 months and 7 years of exposure to the marine medium were thoroughly characterized by X-ray diffraction and μ-Raman spectroscopy. The results obtained for short immersion times (6 and 12 months) revealed a general process leading mainly to magnetite Fe3O4, a typical product of atmospheric corrosion favored by wet/dry cycles, and Fe(III) oxyhydroxides FeOOH. The sulfate green rust GR(SO4 2-), a typical product of marine corrosion, could also be identified as a thin layer on the steel surface underneath magnetite. For longer exposure times (7 years), two behaviors were observed, one similar to atmospheric corrosion, the other similar to the corrosion process occurring during continuous immersion in seawater. This difference is more likely linked to the drying conditions of the rust layer during the emersion periods of the wet/dry cycle. The corrosion rate associated to these two behaviors is also different (~0.09 mm/year in the first case, ~0.05 mm/year in the second case). © 2013 EDP Sciences .


Paugam L.,ACCOAST SAS | Mao A.,ACCOAST SAS | Deborde J.,ACCOAST SAS | Goubert E.,University of Southern Brittany | And 3 more authors.
Materiaux et Techniques | Year: 2013

A study of the electrochemical behavior of metallic structures according to changes of environmental parameters of the water column was conducted in estuarine site of the port of Nantes Saint-Nazaire. The results show that the polarization, the holding of this polarization and the current demand of structures are directly influenced by salinity according to the seasons and the tides. This study opens perspectives in terms of identification of influence factors to anticipate the current demand and optimize the design of cathodic protection in port sites and its monitoring. © 2014 EDP Sciences.


Gueune H.,BP. 48 | Refait P.,University of La Rochelle | Jeannin M.,University of La Rochelle | Sabot R.,University of La Rochelle | And 3 more authors.
Materiaux et Techniques | Year: 2013

Degradations of port structures result from corrosion of carbon steel by seawater. Marine corrosion is mostly generalized (or uniform) corrosion. Nevertheless, accelerated localized corrosion phenomena could be induced by microorganisms. These phenomena are called Microbiologically Influenced Corrosion (MIC). A carbon steel structure with localized corrosion is studied in this paper. The metallic structure is located in Mediterranean Sea, in tidal conditions exhibiting small tidal variations. Physico-chemical (X-Ray diffraction and Raman) and microbiological analyses were performed on deposits covering steel surfaces to try to identify the cause of the degradations. Results show that these deposits are composed of corrosion products and microorganisms (able to influence corrosion mechanisms), commonly found in marine environments. However akaganeite (β-FeO1-x(OH) 1+xClx) is detected inside corrosion craters with high concentrations of acid-producing microorganisms. It seems to reveal an acceleration of corrosion processes due to local acidification by acid-producing microorganisms. © 2014 EDP Sciences .


Jeannin M.,University of La Rochelle | Sabot R.,University of La Rochelle | Antony H.,BP 48 | Pineau S.,Accoast SAS | Refait P.,University of La Rochelle
Materiaux et Techniques | Year: 2013

Carbon steel coupons were set in the tidal zone of two seaports (Le Havre and Nantes-Saint Nazaire) for 7 years with a cathodic protection applied permanently, stopped after 6 years or applied only the last year. The products covering the coupons were thoroughly characterized by X-ray diffraction and μ-Raman spectroscopy, and the corrosion rates were estimated by residual thickness measurements. Permanently protected steel coupons are characterized by corrosion rates ten times smaller than those measured for unprotected coupons. The products of the residual corrosion process, similar to those observed at the open circuit potential, form a thin layer on the steel surface under the calcareous deposit. Stopping cathodic protection after 6 years induces a re-acceleration of the degradation, as revealed by the accumulation of the usual corrosion products. This confirms that cathodic protection has mainly a moderating effect on the kinetics of a process basically unchanged. Finally, the delayed application of the protection can induce the transformation of previously formed corrosion products. For instance, sulfate green rust is integrally transformed into carbonate green rust. Other compounds, such as magnetite, are not affected. The importance of the modifications induced by cathodic protection consequently depends on the composition of the pre-existing rust layer. © 2013 EDP Sciences.


Refait P.,University of La Rochelle | Jeannin M.,University of La Rochelle | Sabot R.,University of La Rochelle | Antony H.,Corrodys | Pineau S.,Accoast SAS
Corrosion Science | Year: 2013

Carbon steel coupons were permanently exposed to seawater in the low water zone of two French harbors for 5. years before to be subjected to cathodic protection (potential about -0.95. V vs. Ag/AgCl/seawater) for 1. year. The application of cathodic polarization to the previously unprotected coupons induced the transformation of GR(SO42-) into GR(CO32-). Other coupons were permanently protected by cathodic protection during the 6. years immersion. A thin film of green rust and mackinawite was observed on the steel surface. This film was covered by a thicker layer of calcareous deposits. © 2013 Elsevier Ltd.

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