Galvanic corrosion of aluminum–steel under two-phase flow dispersion conditions of CO2 gas in CaCO3 solution

Abstract

Abstract Galvanic corrosion of aluminum (Al) and carbon steel (CS) coupled under two-phase flow gas–liquid dispersion conditions was investigated. A disc turbine mixer (Rushton turbine) was used to simulate two-phase flow dispersion conditions. The liquid was a CaCO 3 solution and the dispersed gas was CO 2 . The effects of agitation velocity (0–1000 rpm corresponding to Reynolds number of 0–299,000), CO 2 gas flow rate (0.34–1.6 m 3 /h), temperature (30–50 °C), and time on galvanic corrosion current and loss in weight of both metals in both free corrosion and galvanic corrosion were investigated. The trends of open circuit potential (OCP) of each metal and galvanic potential ( E g ) of the couple were, also, determined. The results revealed that Al was cathodic relative to CS in galvanic couple and its OCP was much more positive than that of CS for all investigated ranges of operating conditions. Increasing the agitation velocity led to a decrease in galvanic corrosion rate and also in free corrosion rate of each metal as well depending on CO 2 pumping rate through the solution. The increase in CO 2 gas flow rate, led to a decrease in galvanic corrosion rate especially at high agitation velocity due to a high dispersion of gas bubbles in the solution. Unstable trend of OCP and E g with agitation velocity and CO 2 gas flow rate was noticed. Clear increase in galvanic currents was observed with increasing temperature of the two-phase system. The galvanic current and the galvanic potential exhibited considerable decrease with time for the majority of the operating conditions.