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On Growth and Stifling of Localized Corrosion Attacks in CO2 and Acetic Acid Environments : Application to the Top-of-Line Corrosion of Wet Gas Pipelines Operated in Stratified Flow Regime
Le 10 Novembre 2009, Institute for Energy Technology (IFE), Norvège
Thèse préparée dans le laboratoire Institute for Energy Technology (IFE, Norway), Laboratoire de Science et Ingénierie des Matériaux et des Procédés (SIMAP, France), Laboratoire d'Electrochimie et de Physicochimie des Matériaux et des Interfaces (LEPMI, France), sous la direction conjointe de M. Ricardo Pereira NOGUEIRA et de M. Egil GULBRANDSEN.
The main goal of this work was to go deeper in the analysis of the qualitative behaviour frequently found in the case of the so-called top-of-line corrosion (TLC), that is, increasing corrosion rates and steep shrinkage after certain - not predictable - time delay. Focus was on the role of acetic acid (HAc) in the growth and stifling of localized attacks in CO2-containing media. The kinetic behaviour of carbon steel in such brine indicated that the dissolution processes are not straightforwardly related to the presence of HAc but rather to what is generically referred to as CO2 corrosion. ZRA measurements on artificial pit electrode assembly, showed that the pit growth is self-sustained only to a certain critical depth, beyond which the coupling current sharply drops off as it effectively occurs in actual TLC cases. Numerical simulation results showed that pits are likely to propagate and stifle mainly according to the counteracting depletions of HAc and CO2.