A joint experimental and theoretical investigation of the corrosion inhibition behavior and mechanism of hydrazone derivatives for mild steel in HCl solution.

• The studied inhibitors were synthesized from Naproxen-based hydrazones. • They have a good inhibition effect for the corrosion of mild steel in 1 M HCl solution. • Results from electrochemical and weight loss measurements are quite comparable. • Adsorption of hydrazone derivatives followed Langmuir isotherm model. • All the experimental results showed good agreement with DFT and MD studies and explained adsorption mechanism. Increasing scientific focus has recently been placed on inhibiting the corrosion of metals and their alloys in acidic environments. In doing so, an understanding and explanation of the adsorption of two environmentally friendly corrosion inhibitors, namely (E)-2-(6-methoxynaphthalen-2-yl)-N'-(1-phenylethylidene)propanehydrazide (PHD-H) and (E)-N'-(1-(4-bromophenyl)ethylidene)-2-(6-methoxynaphthalen-2-yl)propanehydrazide (PHD-Br) on a mild steel (MS) surface in 1.0 M HCl solution and their inhibition efficiency was sought in this study. To this end, both electrochemical and theoretical approaches were used to evaluate the anticorrosive effect of two studied compounds. Based on the obtained results, it was apparent that both inhibitors showed excellent protective efficacy, with PHD-Br compound showing the best inhibition performance reaching 95 % at 5 × 10−3 M. Experimental results obtained by electrochemical techniques indicated that the presence of PHD-H and PHD-Br compounds significantly increased the polarization resistance and affected anodic and cathodic reactions, i.e., mixed type inhibitors. Besides, their adsorption followed the Langmuir isotherm model. The stability of the PHD-Br at higher temperatures (303 K–333 K) was investigated by weight loss measurements. To explain this observed efficiency-temperature relationship, the same extreme temperature conditions have been studied theoretically by molecular dynamics (MD) simulations. In addition, the study revealed that a protective barrier was formed by adsorption of the investigated compounds on the surface of the MS, which is confirmed by scanning electron microscopy with energy-dispersive x-ray analysis (SEM-EDX) analysis. Beyond this, Density Functional Theory (DFT), MD simulation and radial distribution function studies have been carried out. Their theoretical results, which are in good agreement with the experimental ones, have shown that corrosion inhibition performance is a result of strong donor-acceptor interactions between the inhibiting compounds and the metal surface. This study provides an approach based on electrochemical and theoretical techniques to control the mild steel loss by using new naproxen-based hydrazones that are anticipated to inhibit the corrosion of steel in an acidic medium. [ABSTRACT FROM AUTHOR]