LAUSR

Abstract In this paper, a novel nanoemulsion-based strategy used to improve the corrosion inhibition effect of plant extracts. A corrosion inhibitor was Zataria multiflora (Shirazi thyme) extract. GC–MS analyzes, FTIR spectroscopy, and dynamic light scattering were used to study the composition, chemical structure, and particle size of Thyme extract and nanoemulsion. Nanoemulsion prepared with anionic surfactant (sodium dodecyl sulfate) had hydrodynamic diameters smaller than 20 nm with narrow particle-size distribution. The inhibition efficiency was calculated using weight loss tests, electrochemical impedance spectroscopy, and dynamic polarization plots. The results revealed that the inhibition efficiency in the presence of 800 ppm of Thyme extract was 76%. Thyme extract nano-emulsification showed that greater efficiency is achieved in the presence of very small quantity of inhibitor. Corrosion efficiency exposed to 40 ppm of nanoemulsion reached 94%. The inhibitory mechanism of the extract was physical adsorption on the metal surface and followed up the Langmuir adsorption isotherm. The amount of free energy adsorbed by the Thyme extract is about −23 kJ·mol−1. This value reached to −30 kJ·mol−1 by nano-emulsification, which indicates better adsorption and physically chemically adsorption orientation. The Yield of Thyme extracts decreased significantly over long periods when nanoemulsion led to less reduction of yield and also provided a long-term inhibitory effect. The thermodynamic parameters were calculated for further investigation, and the performance mechanism based on the nanoemulsion inhibition was proposed.