CO_2 CORROSION INHIBITION AND OIL WETTING OF CARBON STEEL WITH FERRIC CORROSION PRODUCTS

摘要

Wettability of carbon steel and carbon steel with corrosion product films (iron carbonate (FeCO_3) and FeCO_3 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 CO_2 corrosion tests at 60°C, 1 bar CO_2, 3 Wt-% NaCI 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 FeCO_3 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 Ol enabled the oxidized FeCO_3 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.