Effect of temperature on corrosion behaviour of N80 steel in CO2-saturated formation water

Corrosion behaviour of N80 steel in CO2-saturated formation water was studied by weight loss measurement, electrochemical test and surface characterization. The results showed that the general corrosion rate initially increased and decreased with the increase of temperature and it reached maximum at 60 degrees C about 10 mm/y. The polarization curves showed the similar results on corrosion rate of N80 steel after the exposure experiment in CO2-saturated formation water. Localized corrosion was observed at the temperature of 40 degrees C and 50 degrees C. The XRD pattern indicated that the corrosion product was mainly composed by Fe3C when the temperature under 50 degrees C, then FeCO3 appeared when the temperature was above 50 degrees C. At 70 degrees C, the corrosion product was comprised of FeCO3 totally. Generally, the temperature of 60 degrees C was the turning point for corrosion type and corrosion product transformation in the test conditions.