Exploration of the potentials of imidazole-based inhibitor package for heat exchanger-type stainless steel during acid cleaning operation
Ikenna B. Onyeachu, Moses M. Solomon, Kenneth Kennedy Adama, Chukwuemeka F. Nnadozie, Cornelius C. Ahanotu, Christopher E. Akanazu, Demian I. Njoku
Abstract
Protecting heat exchanger alloys from corrosion during acid cleaning is sacrosanct and necessitates the development and application of highly–efficient environmentally–friendly corrosion inhibitors. In the present work, gravimetry, electrochemical impedance spectroscopy (EIS), cyclic potentiodynamic polarization (CPDP), cyclic voltammetry and scanning electron microscopy-energy dispersive x-ray spectrophotometry (SEM-EDX) have been employed to investigate the potential of 1–benzylimidazole and its mixture with potassium iodide (KI) for the mitigation of stainless steel (SS316L) corrosion in 1 M HCl solution at 60 °C. After short immersion time, 1–benzylimidazole is found to decrease the weight loss and corrosion rate of the substrate and impacts an inhibition efficiency of ≈ 65% at 2000 ppm dosage. The inhibitor adsorption followed the Freundlich isotherm. The synergism significantly lowers the rate of anodic half–reactions involving Fe and Cr oxidation which, in turn, boosts the inhibitor efficiency to > 80% through a competitive synergism. SEM-EDX characterization confirm that the passive layer formed in the presence of 1–benzylimidazole + KI significantly mitigated against the propagation of localized pitting corrosion. Prolonged immersion time, up to 72 h, lowers the inhibition efficiency of 1–benzylimidazole + KI mixture to 74 %.