A critical view of computational chemistry methods in understanding corrosion inhibition of 6-chloro-2- phenylimidazo[1,2-b]pyridazine in 1 M and 5 M HCl

The aim of this article is to highlight some of the pitfalls frequently encountered in the literature. Firstly, deductions based on correlations obtained for a few isolated inhibitors. Secondly, the inability of quantum methods to account for the aggressiveness of the environment. Thirdly, distrust in the interpretation of small differences between energy descriptors in terms of correlation between experimental results and quantum calculations. Finally, the use of overly simplistic surface models. This study highlights the limitations of local reactivity descriptors such as EPF and NPF calculated according to NBO and not according to NPA for the isolated molecule 6-chloro-2-phenylimidazo[1,2-b]pyridazine in both its neutral CP-IPZ and protonated CP-IPZH forms. Also, the calculation of NEBD according to QTAIM, then the calculation of GEDT at the level of the transition states of the iron-CP-IPZH complex. The resulting descriptors take no account of the nature or concentration of the corrosive medium (1 M and 5 M HCl). In addition, DM and MC were used to take account of the concentration of the corrosive solution, inhibitor-metal interactions and the dynamic aspect of the adsorption process. It was shown that despite the difference in adsorption energy of CP-IPZH, which follows the trend in terms of the aggressiveness of the medium, does not reflect the low polarization resistance in 5 M HCl, i.e. ten times lower than that in 1 M HCl.

Automated summary

The article highlights common pitfalls in the literature, including deductions based on isolated inhibitors, the limitations of quantum methods in accounting for environmental aggressiveness, distrust in interpreting small energy descriptor differences, and the use of simplistic surface models. The study focuses on local reactivity descriptors for the molecule 6-chloro-2-phenylimidazo[1,2-b]pyridazine, and highlights the importance of considering the corrosive medium's nature and concentration. DM and MC methods are used to account for inhibitor-metal interactions and the dynamic aspects of the adsorption process. The study reveals that the adsorption energy of CP-IPZH does not reflect the polarization resistance in different concentrations of HCl.