Material Technology

CO2 corrosion inhibition and oil wetting of carbon steel with ferritic corrosion products

Foss, M. , Gulbrandsen, E. , Sjöblom, J.
Corrosion 2009, Atlanta, 2009-03-22-03-26. Paper 09563
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Wettability of carbon steel and carbon steel with corrosion product films (iron carbonate (FeCO3) and FeCO3 with oxidized surface) was investigated through contact angle and inhibitor performance tests. Two corrosion inhibitors, an oleic imidazoline compound (OI) and a phosphate ester compound (PE) were used. The inhibitor performance was studied in CO2 corrosion tests at 60 ºC, 1 bar CO2, 3 Wt-% NaCl and 20 vol-% oil, where the samples were alternately exposed to oil and aqueous phase. A refined, low aromatic, oil was used in the tests. Addition of both surfactants lead to significant changes in the wettability of oxidized FeCO3 surfaces. The contact angle tests showed that a transition from a preferential water-wet state to a preferentially oil-wet state was achieved for both inhibitors. Electrochemical measurements revealed that addition of OI enabled the oxidized FeCO3 surface to retain an oil film after exposure to oil. The retained oil film caused a significant drop in corrosion rate in the presence of oxygen. The effect was also seen on a rusting carbon steel surface without any surface deposits. No similar effect was seen for PE. ©NACE International. All rights reserved. Paper reproduced with permission from CORROSION 2009 Annual Conference and Exhibition, Atlanta.
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