Hydrolysis of imidazoline based corrosion inhibitor and effects on inhibition performance of X65 steel in CO2 saturated brine

The molecular characteristics of a TOFA/DETA based imidazoline inhibitor were evaluated by analysing the inhibitor protonation profile, the CMC and micelle size and the rate of acid-catalysed hydrolysis of the inhibitor to improve understanding of the corrosion inhibition performance of the main imidazoline component and its hydrolysis products. The ability of the TOFA/DETA imidazoline based corrosion inhibitor and its products of hydrolysis in retarding both uniform and localized corrosion were assessed and compared on wet-ground X65 carbon steel at 80 degrees C in CO2 saturated 3 wt % NaCl brines. The findings indicate that the imidazoline based inhibitor forms micellar solutions, with a characteristic micelle size of 18 +/- 9 nm at the CMC (10 +/- 1 ppm) in CO2 saturated 3 wt % NaCl brines, and that under such conditions (pH similar to 4.1), the inhibitor is fully protonated which increases inhibitor solubility/dispersibility and enhances molecular adsorption of the positively charged imidazoline on the metal surface thereby improving inhibition performance. Hydrolysis of the imidazoline and amido-amine is acid-catalysed and the consumption of imidazoline follows a pseudo-first-order reaction mechanism with an activation energy of 72.0 +/- 2.9 kJ mol-1. The study concludes that the pre-aged inhibitor has different effects on uniform and localized corrosion behavior of X65 carbon steel.

Automated summary

The molecular characteristics of a TOFA/DETA-based imidazoline inhibitor were evaluated to understand the corrosion inhibition performance. The inhibitor forms micellar solutions in CO2 saturated NaCl solution, with fully protonated conditions enhancing inhibitor solubility and molecular adsorption on the metal surface. The acid-catalysed hydrolysis of the inhibitor follows a pseudo-first-order reaction mechanism with significant effects on the corrosion behavior of X65 carbon steel.