Relationship between Inhibitor Adsorption and Surfactant Properties: Part Ⅱ - Critical Parameters

摘要

The relationship between corrosion inhibitor adsorption and micellization processes of different types of inhibitor molecules has been evaluated using a recently developed experimental approach. The approach involved integrating the following experimental methodologies - Capacitance vs Potential measurements, Cyclic Voltammetry, Quartz Crystal Microbalance, Surface Tension and Fluorescence Spectroscopy. Homologous series of quaternary amines and hydroxyethyl imidazolines were studied and compared to establish the effect of critical parameters such as pH, salinity, temperature and carbon chain length on the adsorption and micellization process. The two processes have been found to be closely related and depend not only on the surfactant properties (polar head group and carbon chain length), but also on environmental parameters such as temperature, pH and ionic strength. Adsorption isotherms and critical micelle concentrations were determined under different solution conditions and were used to calculate thermodynamic constants - Gibbs free energy (ΔG), enthalpy (ΔH) and entropy (ΔS) change associated with the two processes. The correlation of these constants, which are related to the active components of these inhibitor molecules and solution conditions, can help in developing and characterizing corrosion inhibitors required to be used under challenging conditions in the oil and gas industry.