Most of the carbon dioxide (CO2) corrosion inhibition work published has been based on constituents that behave as surfactants (e.g., quaternary amines and imidazolines). For these compounds, a relationship has been found between the concentration for maximum efficiency and the critical micelle concentration (CMC) and, more recently, with the concentration of maximum adsorption (CMA) on platinum.

This paper shows how the methodology developed to characterize inhibitors based on their CMA values is still applicable to non-surfactant corrosion inhibitors, which would not show a CMC.

The effects of parameters such as pH, salinity, temperature and number of rings in the molecules’ molecular structure on the adsorption process of molecules having a pyridine ring (pyridine, quinoline, and acridine) were evaluated. Adsorption isotherms 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 this process. Additional studies were conducted to understand the effect of protonation on the adsorption properties of these molecules. The correlation between the CMA values obtained in this work and CO2 corrosion inhibition will be presented in another paper.

Subject
Thermodynamics, Adsorption, Sodium chloride, Micelles, Surfactants, Silicate deposits, Platinum, Acidity, Free energy, Sodium chloride solution, Entropy, Salinity, Corrosion inhibitors
Keywords:
Non-surfactant Corrosion Inhibitors, Concentration of Maximum Adsorption
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2021
Association for Materials Protection and Performance (AMPP)
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