Adsorption of Corrosion Inhibitors onto Iron Carbonate (FeCO₃) Studied by Zeta Potential Measurements

Abstract

The adsorption of cetyl trimethyl ammonium bromide (CTAB) and two commercial inhibitor base chemicals, an oleic imidazoline salt (OI) and a phosphate ester (PE), onto iron carbonate (FeCO₃), was studied by zeta potential measurements in a 0.1 wt% sodium chloride (NaCl) solution under 1 bar CO₂ at 22°C, in the absence and presence of a refined low-aromatic oil. The zeta potential of oil-in-water emulsion droplets was also determined. Surface tension of 0.1 wt% and 3 wt% brines was measured as a function of inhibitor concentration. The isoelectric point was pH 6.0 in the 0.1 wt% NaCl solution under 1 bar CO₂. The results show that all three inhibitor compounds adsorbed onto the iron carbonate particles both at pH 4.0 and pH 6.0. Adsorption on both negatively charged surfaces and surfaces with no charge were thus found for all inhibitors. The addition of oil had no significant effect on the measured zeta potential on iron carbonate particles.

Keywords:

• Corrosion inhibitors
• CTAB
• iron carbonate
• oleic imidazoline salt
• phosphate ester
• zeta potential

Acknowledgments

The work is a part of a joint project between Institute for Energy Technology and the Norwegian University of Science and Technology, sponsored by the Research Council of Norway (Project no. 158913/I30).