N, N'-Dialkylcystine Gemini and Monomeric N-Alkyl Cysteine Surfactants as Corrosion Inhibitors on Mild Steel Corrosion in 1 M HCl Solution: A Comparative Study

Ruby Aslam; Mohammad Mobin; Saman Zehra; Ime B Obot; Eno E Ebenso

doi:10.1021/acsomega.7b00501

N, N'-Dialkylcystine Gemini and Monomeric N-Alkyl Cysteine Surfactants as Corrosion Inhibitors on Mild Steel Corrosion in 1 M HCl Solution: A Comparative Study

ACS Omega. 2017 Sep 11;2(9):5691-5707. doi: 10.1021/acsomega.7b00501. eCollection 2017 Sep 30.

Authors

Ruby Aslam¹, Mohammad Mobin¹, Saman Zehra¹, Ime B Obot², Eno E Ebenso³

Affiliations

¹ Corrosion Research Laboratory, Department of Applied Chemistry, Faculty of Engineering and Technology, Aligarh Muslim University, Aligarh 202002, India.
² Centre of Research Excellence in Corrosion, Research Institute, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia.
³ Material Science Innovation & Modelling (MaSIM) Research Focus Area, Faculty of Agriculture, Science and Technology, North-West University (Mafikeng Campus), Private Bag X2046, Mmabatho 2735, South Africa.

Abstract

Gemini surfactant, N,N'-dialkylcystine 2(C₁₂Cys), derived from cystine, and a monomeric N-alkyl cysteine counterpart, (C₁₂Cys), were synthesized and purified. The characterization of surfactants 2(C₁₂Cys) and (C₁₂Cys) was made by Fourier transform infrared, ¹H NMR, and elemental analysis. The effect of 2(C₁₂Cys) and (C₁₂Cys) on mild steel (MS) corrosion in 1 M HCl solution was explored as a function of their concentration and electrolyte temperature by means of gravimetric and electrochemical experiments (potentiodynamic polarization and Electrochemical impedance spectroscopy), surface analytical techniques (scanning electron microscopy (SEM)/energy dispersive X-ray spectroscopy (EDAX) and atomic force microscopy (AFM)) and theoretical study. The investigated compounds exhibited surface active properties and performed as good inhibitors for corrosion control of mild steel (MS) in acid solution. However, compared to monomeric (C₁₂Cys), Gemini surfactant 2(C₁₂Cys) showed high corrosion inhibiting ability at very low concentration. The EIS results revealed a greater charge transfer resistance in 2(C₁₂Cys) solution compared to that in (C₁₂Cys) solution. SEM/EDAX observations validate the development of an inhibitive film by the adsorbed molecules of surfactant on the MS surface. The AFM micrographs supported the SEM/EDAX results and exhibited a lowering in the roughness of the corroded MS surface in the presence of both (C₁₂Cys) and 2(C₁₂Cys) surfactants. Further, quantum chemical calculations and Monte Carlo simulations were used to study the dependence of corrosion inhibiting efficacy on the molecular structure and adsorption strength.