Electrochemical, surface analysis, computational and anticorrosive studies of novel di-imine Schiff base on X65 steel surface
Ahmed Nasser, M.A. Migahed, N.M. El Basiony, Hassan Abdelbary, Tarek A. Mohamed
Abstract
Abstract The inhibitory effect of di-imine-SB namely (( N 1 Z, N 4 E)-N 1 , N 4 -bis (4 (dimethylamino) benzylidene) butane 1,4-diamine) on X65-steel in 1 M HCl has been investigated experimentally and theoretically. The electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), and weight loss outcomes display the anticorrosion properties of “di-imine- SB”. The inhibitory efficiency exceeds 90% at the optimal concentration of 1 × 10 –3 M “di-imine- SB”. The metal surface was examined further using scanning electron microscope (SEM) and energy dispersive X-ray (EDX). The effectiveness of the di-imine-SB is returned into its adsorption on X65-steel surface and found in agreement with Langmuir adsorption isotherm. According to the standard Gibbs free energy of adsorption $$({\Delta G}_{ads}^{^\circ })$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mo>(</mml:mo><mml:msubsup><mml:mrow><mml:mi>Δ</mml:mi><mml:mi>G</mml:mi></mml:mrow><mml:mrow><mml:mi>ads</mml:mi></mml:mrow><mml:msup><mml:mrow/><mml:mo>∘</mml:mo></mml:msup></mml:msubsup><mml:mo>)</mml:mo></mml:mrow></mml:math> , di-imine-SB adsorption tends to be chemical rather than physical, it increases the activation energy ( $${\mathrm{E}}_{a}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>E</mml:mi><mml:mi>a</mml:mi></mml:msub></mml:math> ) of metal dissolution reaction and makes it hard to occur. The PDP data suggested anodic and cathodic type of the di-imine-SB inhibitor. Meanwhile, increasing the resistance of X65-steel to 301 Ω cm 2 after adding 1 mM of di-imine-SB confirms its protective effect. Whereas, the positive value of the fraction of electron transference (ΔN, 0.746), confirms the affinity of di-imine-SB to share electrons to the partially filed 3d-orbital of Fe forming strong protective film over X65-steel surface. Aided by Monte Carlo (MC) simulation, the calculated adsorption energy (E ads ) suggests excessive adsorption affinity of di-imine-SB on metal surface over the corrosive chlorides and hydronium ions. A good correlation between the theoretical hypothesis and the experimental inhibition efficiency has been achieved. The comparative study showed the superior of the di-imine-SB as potential corrosion inhibitor compared with those reported before. Finally, global reactivity descriptors; electron affinity ( A ), ionization potential ( I ), electronegativity ( χ ), dipole moment ( µ ), global hardness ( $$\eta$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>η</mml:mi></mml:math> ), electrophilicity index and, Fukui indices were also calculated and found well correlated to the reactivity of di-imine-SB.