Abstract
Although inhibitor adsorption and inhibition mechanisms have been studied extensively using various electrochemical techniques, these electrochemical techniques only provide an indirect estimate of inhibitor adsorption. Quartz crystal microbalance (QCM) has been shown to be a powerful acoustic technique which can be effectively used to evaluate net mass adsorption of inhibitors, adsorption rates and kinetic coefficients. In the present study, calibration of QCM by electrochemical deposition of copper on gold-coated quartz crystal resonator was done to evaluate the minimum mass change that can be determined using these devices. Sensitivity coefficient was measured within 5% accuracy for QCM-D equipment vs. within 20% accuracy for oscillatory circuit based-QCM equipment. Also, a different oscillatory circuit based-QCM equipment was used with flow cell to investigate the adsorption of tetra-decyl-dimethyl-benzyl-ammonium (Q-C14) inhibitor model compound on gold-coated quartz crystal resonator. Analysis of experimental data indicated that the inhibitor was adsorbed on the gold surface within a few minutes and the net amount of inhibitor adsorbed depends upon the bulk inhibitor concentration. However, the rate of frequency change for adsorption and desorption processes did not vary much for two inhibitor concentrations (50 ppm(w) and 100 ppm(w)) used for this study. This calls for further investigation of inhibitor adsorption at different concentrations.
