Canadian Journal of Chemical Engineering, Vol.86, No.2, 240-248, 2008
Corrosion inhibition of carbon steel under two-phase flow (water-petroleum) simulated by turbulently agitated system
The corrosion of carbon steel in single-phase (water with 0.1 N NaCl) and two immiscible phases (kerosene-water) using turbulently agitated system was investigated. The experiments were carried out for Reynolds number (Re) range of 38 000 to 95 000 using circular disc turbine agitator at 40 degrees C. In two-phase system, test runs were carried out in aqueous phase (water) concentrations of 1% vol, 5% vol, 8% vol, and 16.4% vol mixed with kerosene at various Re. The effect of Re, percent of dispersed phase, dispersed droplet diameter, and number of droplets per unit volume on the corrosion rate were investigated and discussed. Test runs were carried out using two types of inhibitors: sodium nitrite of concentrations 20, 40, and 60 ppm and sodium hexapolyphosphate of concentrations 485, 970, and 1940 ppm in a solution containing 8% vol aqueous phase (water) mixed with kerosene (continuous phase) at 40 degrees C for the whole range of Re. It was found that increasing Re increased the corrosion rate and the presence of water enhanced the corrosion rate by increasing the solution electrical conductivity. For two-phase solution containing 8% vol and 16% vol of water, the corrosion rate was higher than single phase (100% vol water). The main parameters that play the major role in determining the corrosion rate in two phases were concentration of oxygen, solution electrical conductivity, and the interfacial area between the two phases (dispersed and continuous). Sodium nitrite and sodium hexa polyphosphate were found to be efficient inhibitors in two-phase solution for the investigated range of Re.