Measurements of Zeta Potential on Corroding, High-Purity Iron Particles: Influence of Corrosion Inhibitors

Abstract

Adsorption of cetyl trimethyl ammonium bromide (CTAB), and two commercial inhibitor base chemicals; an oleic imidazoline salt (OI) and a phosphate ester (PE), onto high purity, corroding iron particles was studied by zeta potential measurements in a 0.1 Wt% sodium chloride (NaCl) solution under 1 bar CO₂ at 22°C. The particles were exposed to the inhibitor compounds for 24 hours before measurements were done. The results show that the measured zeta potential in the absence of inhibitor is zero at both pH 4.0 ± 0.2 and pH 5.8 ± 0.2. It is concluded that this might be caused by the electrochemical reactions occurring at the steel surface when placed in an electrical field. When adding inhibitor, which slows the electrochemical reactions at the steel surface, the zeta potential moves away from zero and an adsorption isotherm is obtained for all three inhibitors. The measured potential is probably a mixed potential where the apparent potential measured is a combination of the potential at the shear plane and a contribution form the electrochemical reactions occurring on the surface.

Keywords:

• Corrosion inhibitor
• CTAB
• oleic imidazoline
• 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).