Exploring the potential of isonicotinohydrazide derivatives in N80 steel corrosion control: An integrated approach through synthesis, modeling, and experimentation in acidic environments

Abstract

N80 carbon steel (N80CS) is recognized for its superior mechanical properties and cost-effectiveness. However, its susceptibility to corrosion, particularly in hydrochloric acid (HCl) environments, necessitates the exploration of corrosion inhibitors. This research centers on the evaluation of N′-[(Z)-(4-bromophenyl)methylidene]pyridine-4-carbohydrazide (BBI) and N′-[(1Z)− 1-(4-chlorophenyl)ethylidene]pyridine-4-carbohydrazide (CEI), green organic compounds from the isonicotinohydrazide family, as potential eco-friendly and non-toxic inhibitors for N80CS in a 15 wt% HCl solution. An array of investigative methods, including weight loss measurements, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PDP), were employed to examine the corrosion inhibition performance of these compounds for the N80CS surface in a strong HCl medium. Our experimental findings demonstrated that the inhibitors' efficiency was concentration-dependent, enhancing as concentrations ranged from 10−4 mol/L to 5 × 10−3 mol/L. Notably, BBI's inhibitory efficiency varied between 97.6% and 99.28%, while CEI's ranged from 94.31% to 98.44%. PDP curves elucidated the capability of BBI and CEI to control both anodic and cathodic reactions, thereby classifying them as mixed-type corrosion inhibitors. The improved inhibition efficiency was evidenced by the decrease in double-layer capacitance, supporting the formation of a protective layer that delays the corrosion process. Consistent with the Langmuir adsorption isotherm model, our results suggested these inhibitors involved in both physical and chemical interactions with the iron atoms on the steel surface. This protective formation was further corroborated by scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses, which highlighted a significant reduction in the surface roughness of N80CS. Supplementing our experimental data, theoretical investigations using Density Functional Theory (DFT) and semi-empirical Density functional tight binding (DFTB) simulations were conducted. They confirmed the advantageous reactivity of BBI and CEI, attributable to their molecular structures, which promote facile adsorption onto the Fe(110) surface through covalent bonding. This research provides valuable insights into developing non-toxic and environmentally benign corrosion inhibitors for N80CS in acidic conditions.