Corrosion Inhibition of Mild Steel in Acidic Media by N -[(3,4-Dimethoxyphenyl)Methyleneamino]-4-Hydroxy-Benzamide
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Corrosion Inhibition of Mild Steel in Acidic Media by N‑[(3,4‑Dimethoxyphenyl)Methyleneamino]‑4‑Hydroxy‑Benzamide Kashmitha Muthamma1 · Preethi Kumari1 · M. Lavanya2 · Suma A. Rao1 Received: 19 June 2020 / Revised: 7 October 2020 / Accepted: 14 October 2020 © The Author(s) 2020
Abstract Mild steel (a low carbon steel) is an affordable engineering material used for many purposes in various environments including mild acidic environment with some precautions. The corrosion behaviour of mild steel (MS) in 0.5 M H 2SO4 and 0.5 M HCl, in the temperature range (303–323 K) without and with the inhibitor N-[(3,4-dimethoxyphenyl) methyleneamino]4-hydroxy-benzamide (DMHB), was investigated using Potentiodynamic polarization and Electrochemical impedance spectroscopy (EIS) techniques supplementing with surface characterization study using scanning electron microscope (SEM) and atomic force spectroscopy (AFM). Experimental observations were found to be in agreement with Density functional theory (DFT) calculations. The inhibition efficiency increases with increase in DMHB concentration and showed maximum inhibition efficiency of 86% in 0.5 M H 2SO4 and 81% in 0.5 M HCl, respectively, at concentration of 3 × 10─3 M at 303 K. The inhibition efficiency of DMHB obtained relatively at its lower concentration (3 × 10─3 M) compared to other reported related compounds confirms its potential towards corrosion inhibition. The variation in the kinetic and thermodynamic parameters indicated physisorption of DMHB on MS and its mixed type inhibitive action followed Langmuir’s isotherm model. DFT calculations go along with the experimental results, signifying the potential corrosion inhibition behaviour of DMHB for MS in both the acid media. Keywords Mild steel · Impedance · Physisorption · Langmuir isotherm Abbreviations MS Mild steel DMHB N-[(3,4-Dimethoxyphenyl) methyleneamino]-4-hydroxy-benzamide SEM Scanning electron microscope AFM Atomic force microscope DFT Density functional theory EIS Electrochemical impedance spectroscopy HCl Hydrochloric acid medium H2SO4 Sulphuric acid medium PDP Potentiodynamic polarization OCP Open-circuit potential
* Suma A. Rao [email protected] 1
Department of Chemistry, Manipal Institute of Technology, Manipal Academy of Higher Education, Manipal 576104, India
Department of Chemical Engineering, Manipal Institute of Technology, Manipal Academy of Higher Education, Manipal 576104, India
2
Ecorr Corrosion potential icorr Corrosion current density CR Corrosion rate %IE Percentage Inhibition efficiency θ Surface coverage CPE Constant phase element
1 Introduction Mild steel is an affordable engineering material by virtue of its properties such as strength, ductility, toughness, malleability, machinability and weldability. It finds applications in automobile body components, structural shapes, sheets, etc. The microstructure consists of ferrite and pearlite and has tensile strength in the range 415–550 MPa [1]. Material is used in various environments including mild acidic env
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