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Susceptibility to corrosion damage of pipeline steels under coating disbondments
Author(s) -
Guermazi N.,
Ibrahmi A.,
Hmidi H.,
Elleuch K.,
Ayedi H. F.
Publication year - 2010
Publication title -
materials and corrosion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.487
H-Index - 55
eISSN - 1521-4176
pISSN - 0947-5117
DOI - 10.1002/maco.200905233
Subject(s) - corrosion , materials science , gravimetric analysis , seawater , metallurgy , coating , carbon steel , artificial seawater , rust (programming language) , oxide , chloride , aqueous solution , composite material , chemistry , oceanography , organic chemistry , computer science , programming language , geology
Abstract This study provides an experimental investigation on the corrosion behaviour of three carbon steels used for pipeline application. The susceptibility of these materials to corrosion damage was analysed in order to simulate its service conditions particularly under disbonded coating. Monitoring of open‐circuit potential ( E free ), polarization resistance ( R p ) and measuring of the weight loss during immersion time were used to evaluate the corrosion behaviour of the studied materials. All the corrosion experiments were performed in two aqueous solutions: natural seawater and synthetic one (3 wt% NaCl solution). The morphology of the corrosion products was examined by optical microscopy. The results obtained from electrochemical tests have shown different behaviour for the studied steels into the retained corrosive environments: more stable potentials ( E free ), higher R p ‐values with large fluctuations evolution were found in natural seawater. The gravimetric measurements have also shown a continuous variation of the weight loss throughout the exposure period in the sodium chloride solution. However, it seemed that a passive behaviour was observed in natural seawater. A little difference was observed between all the studied steels in terms of corrosion kinetics. The steel, having the little ferritic grain size, seems to be more resistant to corrosion damage. Qualitatively, a porous and non‐adherent oxide film was observed on the corroded surface in the synthetic solution; while, the rust layer, which is formed in the natural seawater, has acted as a barrier of corrosion process. Finally, all the results obtained from both electrochemical tests and weight loss measurements were in reasonably good accordance. The important common point that can be concluded was that all the tested materials seem to be more suitable for natural seawater than 3 wt% NaCl solution. Also, they are not recommendable to be used in an environment where chloride attack is possible and important.