CORROSION UNDER TWO – PHASE FLOW KEROSENE / WATER SIMULATED BY TURBLENTLY AGITATED SYSTEMS

The corrosion of carbon steel in agitation systems of single phase (1% wt. NaCl solutions) and two phases (1% wt.NaCl solutions / Kerosene) were investigated by weight loss and polarization techniques. In single aqueous phase the weight loss experiments were carried out at different rotational velocities (262, 349, 438, 525, 600, 612, 800, 1000, 1200 and 1400) rpm using circle disk turbine agitator of 8 cm diameter.The average corrosion rate increased with increasing rotational speed. The Polarization experiments were carried out at the same rotational velocities as in weight loss. The limiting currents (i.e. average corrosion rate) were found to support the results obtained by weight loss technique, i.e., limiting current increased as rotational velocity increased too.In two-phase system (1%wt. NaCl solution /
Kerosene) investigation was performed by weight loss technique only due to the high electric resistance of agitated solutions. These test runs were carried out in aqueous phase concentrations 1% vol., 5 % vol., 8% vol., and 16.4% vol. of 1% wt. NaCl solutions mixed with kerosene at rotational velocities of 600, 800, 1000, 1200, and 1400 rpm. The average corrosion rate increased with increasing speed of rotation in all aqueous concentrations. Furthermore, the average corrosion rate can be stated to increase with Reynolds number, Weber number and inversely with Sauter mean diameter.The effect of phase oncentration was noted to be dependent on aqueous phase concentration as follows: In low range aqueous phase (1%wt. NaCl solution) concentrations of 1% vol., and 5% vol., the average corrosion rate increased as aqueous phase concentration increased at Reynolds number of 38428, 51238, 64047, 76856, and 89666. Furthermore these average corrosion rates were lower than those in single aqueous phase (1% wt. NaCl solution) at equivalent Reynolds numbers.Using high range aqueous phase (1% wt. NaCl solutions)concentrations of 8% vol., and 16.4% vol., the average corrosion rate increased as phase concentration increased, and they were higher than those in single aqueous phase of 1% wt.NaCl solutions at equivalent Reynolds number.Effect of inhibitor: Test runs were carried out using two types of inhibitors (sodium nitrite, and sodium hexapolyphosphate) in 8% vol. aqueous phase mixed with kerosene only. In presence of these two types of inhibitors when speed of rotation was increased the percent protection decreased, while the average corrosion rates decreased when the concentration of inhibitors increased. Sodium hexapolyphosphate is found more efficient as inhibitor than sodium nitrite. At 20, 40, and 60 ppm sodium hexapolyphosphate, the inhibition efficiency was found to be 67.43 to 58.71%, 84.79 to 48.8%, and 93.46 to 58.75% respectively as the speed of rotation (i.e., Re) was changed from 600 to 1400 rpm. Under similar conditions, sodium nitrite at 485, 970, and 1940 ppm, the percent protection was 57.53 to 36.41%, 69.32 to 49.78%, and 86.4 to 94.58% respectively.