Detailed experimental performance of two new pyrimidine-pyrazole derivatives as corrosion inhibitors for mild steel in HCl media combined with DFT/MDs simulations of bond breaking upon adsorption

The corrosion inhibitory potency of two new pyrimidine-pyrazole derivatives, namely N-((3,5-dimethyl-1 H-pyrazol-1-yl) methyl) pyrimidin-2-amine (PPA) and ethyl 5-methyl-1-((pyrimidin-2-yl amino) methyl)− 1 H-pyrazole-3-carboxylate (PPC), was evaluated by mass loss measurements and electrochemical assays for mild steel (MS) in 1 M HCl at 308 K. In this survey, PPA and PPC products were chosen as inhibitors owing to their environmentally friendly formulation and biodegradability, which aligns with the growing demand for sustainable compounds. Besides, the molecular structure of PPA and PPC was precisely designed to provide higher effectiveness towards corrosion. The derived results revealed that the inhibition activities of both PPA and PPC were enhanced with concentration increase reaching maximal values of 91.15% and 92.39% for PPA and PPC, respectively. Conversely, the mitigation potency dropped by approximately 42.28% (for PPA) and 31.30% (for PPC) as the temperature increased from 308 to 348. PDP plots revealed that PPC and PPA is mixed type inhibitor in 1 M HCl. The adsorption mechanisms of the two inhibitors was examined on micro/nano level with scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The derived outcomes indicated high inhibition performance owing to the adsorption of PPA and PPC on MS surface, forming thus a shielding layer that precludes the MS dissolution in the acidic solution. The experimental findings were further confirmed by theoretical descriptors obtained from DFT and Molecular dynamics simulation (MDS) investigations. [Display omitted] •The inhibition efficiency of PPA and PPC molecules was studied on mild steel (MS) in molar hydrochloric solutions.•Surface analysis via SEM and XPS evidenced the presence of inhibitor barrier film.•The adsorption process was elucidated by using DFT calculations and MD simulations.•PPA and PPC molecules adopts a parallel configuration over the iron (111) surface.•The main driving force for the adsorption are the attractive π–π stacking interactions.