DEVELOPMENT OF STANDARD TEST METHOD FOR INVESTIGATION OF UNDER-DEPOSIT CORROSION IN CARBON DIOXIDE ENVIRONMENT AND ITS APPLICATION IN OIL AND GAS INDUSTRY

The under-deposit corrosion of 1030 carbon steel in a carbon dioxide environment has been studied using surface characterization and electrochemical techniques. The effect of a sand deposit on the surface morphology has been investigated using scanning electron microscopy and grazing incidence X-ray diffractometry. An iron carbide phase was identified on the sand-covered surfaces. Potentiodynamic experiments gave a negative shift in the corrosion potential of ~40 mV for the steel surfaces covered with sand deposit. An imidazoline-based inhibitor was found to have little effect on the kinetics of the cathodic reaction and did not provide significant corrosion protection to the covered steel surfaces. The aspects of the inhibition mechanisms have been discussed in terms of the surface characteristics of the steel in the absence and presence of sand deposit. Keywords: Under-deposit corrosion, carbon dioxide, corrosion inhibitor, iron carbide, scanning electron microscopy, grazing incidence X-ray diffractometry.