Inhibitive assessment of 1-(7-methyl-5-morpholin-4-yl-thiazolo[4,5-d]pyrimidin-2-yl)-hydrazine as a corrosion inhibitor for mild steel in sulfuric acid solution

Abstract

In this study, the inhibitive effect of synthesized 1-(7-methyl-5-morpholin-4-yl-thiazolo[4,5-d]pyrimidin-2-yl)-hydrazine (MMTPH) as a new corrosion inhibitor for mild steel in 0.5 M sulfuric acid medium is investigated employing potentiodynamic polarization, electrochemical impedance spectroscopy and linear polarization resistance techniques. The results show MMTPH reduces anodic dissolution, retards the hydrogen evolution reaction and its adsorption follows Langmuir’s adsorption isotherm. Any increase in temperature will in turn increase corrosion current densities; however, the presence of MMTPH hinders the rate. In solutions with inhibitor concentration of 200 ppm, temperature elevations as great as 30° (25–55 °C) result in a drop of about 45 % in inhibition efficiency (99–55 %). Thermodynamic adsorption parameters show that the MMTPH is absorbed by a spontaneous exothermic process and the adsorption mechanism is physical. Quantum chemical method shows that the MMTPH molecules can be directly adsorbed at the steel surface on the basis of donor–acceptor interactions between π-electrons of pyrimidine, N atoms of hydrazine and vacant d-orbitals of iron atoms.