The corrosion behavior of API 5L X65 carbon steel was investigated under high pressure CO2 environments, containing small amount of H2S, to simulate the condition of high CO2 containing natural gas transporting offshore pipeline in Malaysia. It was systematically studied under high pressure CO2 (range from 80 and 120 bars) with variation in other key parameters (temperature, water partitioning and H2S concentration). The corrosion rates were measured using the techniques such as linear polarization resistance (LPR), electrochemical impedance spectroscopy (EIS) and weight loss (WL). The surface morphology and the composition of the corrosion product layers were analyzed by using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The results showed that in the water-rich phase, the addition of 200 ppm H2S instantaneously decreased the corrosion rate of API 5L X65 at both 25°C and 80°C (120 bar). It was also observed that the corrosion rates of API 5L X65 (at both 25°C and 80°C) in the water-saturated CO2 phase are lower than the Minimum Acceptable Corrosion Rate (MACR) of 0.1 mm/year. The addition of H2S increased the corrosivity of this phase. On the hand, insignificant corrosion was observed in the under-water-saturated CO2 phase, even with the presence of 200 ppm H2S.

This content is only available via PDF.
You can access this article if you purchase or spend a download.