Colloids and Surfaces A: Physicochemical and Engineering Aspects xxx (xxxx) 126373 Contents lists available at ScienceDirect Colloids and Surfaces A: Physicochemical and Engineering Aspects Synthesis, structural analysis and corrosion inhibition application of a new indazole derivative on mild steel surface in acidic media complemented with DFT and MD studies Mohammed Boulhaoua a, b , Mohamed El Haf b , Saman Zehra c , Larbi Eddaif d , Awad A. Alrashdi e, ⁎ , Sanae Lahmidi b , Lei Guo f , Joel T. Mague g , Hassane Lgaz h, 1, ⁎ a Institute of Ch emistry, ELTE Eötvös Lo ránd University, Pázmány P. sétány 1/A, Budapest, 1117, Hu ngary b La borato ry of He terocyclic Organic Ch emistry, Department of Ch emistry, Fa culty of Sciences, Mo ha mmed V University in Ra bat, BP, 1014, Ra bat, Mo rocco c Co rrosion Research La borato ry, Department of Applied Ch emistry, Fa culty of Engineering an d Techno logy, Aligarh Mu slim University, Aligarh, India d Doctoral Scho ol of Ma terial Sciences and Techno logies, Óbuda University, Fa culty of Light Industry and Environmental Engineering, Budapest, Hu ngary e Ch emistry Department, Umm Al-Qura University, Al-Qunfud ah University Co llege, Sa ud i Arabia f Scho ol of Ma terial and Ch emical Engineering, Tongren University, Tongren, 554300, Ch ina g Department of Ch emistry, Tulane University, New Orleans, LA, 70118, USA h Department of Crop Science, Co llege of Sanghur Life Science, Konkuk University, Seoul, 05029, So uth Korea ARTICLE INFO Keywords: Corrosion inhibition Indazole derivative Nitro compound XRD DFT Molecular dynamics ABSTRACT A great deal of consideration has been given to the development of new compounds having diverse functionality. In this report, a new indazole derivative bearing a nitro group, namely 2-(3-chloro-5-nitro-1H-indazol-1-yl) acetic acid (CNIA) was synthesized, characterized, and used as corrosion inhibitor for mild steel (MS) in 1.0 M HCl. A full characterization of the prepared compound was performed using single-crystal XRD, FT-IR, and UV–vis measurements; its corrosion inhibition properties were experimentally evaluated by potentiodynamic po- larization (PDP) curves as well as electrochemical impedance spectroscopy (EIS) measurements, and theoreti- cally by Density Functional Theory (DFT) and molecular dynamics (MD) simulations. Scanning electron micro- scope (SEM) was used to examine the morphology of the corroded metal surface before and after the inhibition. The fndings demonstrated that the application of CNIA significantly reduced the corrosion rates of MS. The cor- rosion inhibition ability of the synthesized compound was also identifed at a lower concentration in all experi- ments, reaching a maximum of 89 % at 10 −3 mol/L. The results of potentiodynamic polarization curves and elec- trochemical impedance spectroscopy (EIS) confrmed that CNIA could be categorized as a mixed type inhibitor with an increased polarization resistance at higher concentrations. Langmuir's adsorption isotherm was found to ft the adsorption of CNIA molecules on the MS surface. SEM photographs showed obvious less-corroded mor- phologies in the presence of the CNIA as compared to untreated MS surface. Theoretical calculations were pro- posed to explain the mechanism of the inhibition effect and found that it is due to the donor/acceptor properties of the inhibitor and its parallel disposition over the steel surface. The present compound could be a promising corrosion inhibitor for mild steel in HCl solutions, and showed a corrosion inhibition property that is superior to similar compounds. 1. Introduction The mild steel is currently used in many commercial applications, in- cluding the processing, refning and mining of gas and oil industries, water pipes, cooling water systems, boilers, and skyscrapers [1–4]. Its widespread usage as an industrial input is encouraged by its low cost, affordability, and ease of processing. The steel is, however, vulnerable to numerous modes of corrosion, which is described as a physicochemi- cal reaction between the metal and the environment, leading to a change in the properties of the metal and corrosion as well [5–7]. Cor- rosion is, therefore, a dangerous condition that decreases the properties of materials and makes them unusable. In several sectors, where acids ⁎ Corresponding authors. E-mail addresses: aarashdi@uqu.edu.sa (A.A. Alrashdi), hlgaz@hanyang.ac.kr (H. Lgaz). 1 Present address: Department of Architectural Engineering, Hanyang University-ERICA, 1271 Sa 3-dong, Sangnok-gu, Ansan, 15588, Korea. https://doi.org/10.1016/j.colsurfa.2021.126373 Received 19 December 2020; Received in revised form 10 February 2021; Accepted 17 February 2021 0927-7757/© 2021