Anti-corrosion behavior of 2-(((4-((2-morpholinoethyl)(pyridin-2-ylmethyl)amino)butyl)imino)methyl)naphthalen-1-ol on mild steel in hydrochloric acid solution: Experimental and theoretical studies

A naphthalene derivative, namely 2-(((4-((2-morpholinoethyl)(pyridin-2-ylmethyl)amino) butyl) imino)methyl) naphthalen-1-ol (HL) was synthesized and its chemical structure characterized by spectroscopic techniques (H-1, C-13 Nuclear magnetic resonance, Fourier-transform infrared spectroscopy and Mass spectroscopy). Its action as a corrosion inhibitor against the corrosion of mild steel in 1.0 M HCl solution was fully investigated at ambient temperature using weight loss measurements, potentiodynamic polarization, and electrochemical impedance spectroscopy techniques. The results indicated inhibition efficiency for HL at 100 ppm concentration of greater than 90%. It was determined that the adsorption of HL molecules on the metallic surfaces occurred through the heteroatoms, based on a combination of physical and chemical mechanisms (calculated value of Delta G(ads)(0) was -23.1 kJ/mol) and followed a Langmuir adsorption process leading to a reduction in electric double layer capacitance (20.40 mu F.cm(-2) at 100 ppm concentration). The highest occupied molecular orbital and lowest unoccupied molecular orbital calculations demonstrated that the existence of nitrogen and oxygen atoms in the morpholine and pyridine groups of the protonated form of the molecule assisted in the formation of stronger bonds with the surface of the metal, as an electrophilic agent.