Effect of akyl chain length, flow, and temperature on the corrosion inhibition of carbon steel in a simulated acidizing environment by an imidazoline-based inhibitor

An imidazoline, 2-heptadecyl-1-[2-(octadecanoylamino)ethyl]-2- imidazoline (QSI) with -C₁₇H₃₅ as the tail chain length was synthesized, characterized, and studied as corrosion inhibitor for low carbon steel in 15% HCl solution under static and hydrodynamic conditions. Influence of addition of KI, temperature, and chain length of pendant hydrocarbon on inhibition efficiency (η) was also examined. It is found that, QSI exhibits a mixed type behavior but fairly inhibited the corrosion of low carbon steel in the studied medium. The maximum concentration studied (400 mg/L) afforded η of <50%. Addition of KI to QSI synergistically enhanced the corrosion inhibition performance of QSI, upgrading the η to approximately 90%. Increase in the system temperature increases the η of both QSI and QSI + KI. From the variation of η with temperature and the calculated corrosion kinetic parameters, chemical adsorption is proposed as the adsorption mechanism of the additives. QSI performs better under hydrodynamic condition than static condition. However, the corrosion resistance of the metal decreases at rotation speed higher than 1000 rpm. Inhibition efficiency of imidazoline decreases as the length of the hydrocarbon pendant chain increases. Imidazoline compounds with -C₁₃H₂₇ and -C₁₅H₃₁ as the length of the pendant group hydrocarbon perform better than QSI with -C₁₇H₃₅.