Corrosion of a material by reaction with a corrosive environment is a common problem across many industries. Iraq is an oil country and corrosion represents a large portion of the total costs for oil producing and a natural potential hazard associated with oil production and transportation. The synthesis of novel thiosemicarbazone, namely 2-(2,4-dimethoxybenzylidene)hydrazinecarbothioamide (DMBHC), was conducted and the chemical structure was elucidated via the 1H and 13C NMR (Nuclear magnetic resonance), and FT-IR (Fourier-transform infrared) spectroscopic spectroscopic techniques in addition to carbon, hydrogen, and nitrogen analyses (CHN analyses). The inhibition properties of the investigated thiosemicarbazone were evaluated for mild steel (MS) corrosion in 1N H2SO4 using electrochemical impedance spectroscopy (EIS), weight loss method, and scanning electron microscopy (SEM). Electrochemical and weight loss techniques revealed that the tested thiosemicarbazone acted as a superior inhibitor for the acidic corrosion of MS and the efficiency increased with increasing concentrations. The EIS results revealed that thiosemicarbazone demonstrated the highest inhibition efficiency of 94.86%, at a concentration of 0.5 mM. Results from the weight loss technique suggested that the thiosemicarbazone acted as a mixed type corrosion inhibitor. The impact of temperature on the mechanism of inhibition of the new synthesized inhibitor of the surface of MS in 1N H2SO4 was investigated at various temperatures (30–60 °C) where the inhibitive efficiency diminished with increasing temperatures. The mechanism of inhibition was additionally verified with the methodological data.

No abstract

The corrosion inhibition efficiency of the novel pyridine namely, 4-(Benzoimidazole-2-yl)pyridine has been studied for mild steel in a 1 M hydrochloric acid environment by utilizing gravimetrical techniques. The synthesized inhibitor exhibits a significant inhibitive efficiency of 93.8% at 0.005 M. The adsorption isotherm of the investigated inhibitor on mild steel surface obeys the Langmuir isotherm. Surface morphology investigated by utilizing scanning electron microscopy (SEM) demonstrates a smooth metal surface with the addition of 4-(Benzoimidazole-2-yl)pyridine in a hydrochloric acid environment. Quantum chemical calculations using density functional theory (DFT) have been used to investigate the molecular structure and behavior of 4-(Benzoimidazole-2-yl) pyridine as a corrosion inhibitor. Different parameters have been calculated using DFT, such as energies of highest occupied molecular orbital and lowest occupied molecular orbital (EHOMO and ELUMO), energy gap (∆E), and dipole moment (μ). These parameters were important to elucidate the behavior of the investigated molecule as a corrosion inhibitor in acidic solution and also suggest the mechanism of inhibition.

The inhibition efficiency of a new coumarin derivative, namely 2-(6-methylcoumarin-4-yl)-N´-(3-nitrobenzylidene)acetohydrazide (MCNAH), in controlling corrosion of mild steel in 1 M hydrochloric acid solution was investigated by gravimetric techniques at various temperatures (303, 313, 323 and 333 K). The impact of immersion time and temperature on inhibition performance of MCNAH was also studied. MCNAH was synthesized and the chemical structure was elucidated by magnetic resonance spectroscopy (MRS) and Fouriertransform infrared spectroscopy (FT-IR). The experimental results suggested that MCNAH is an excellent corrosion inhibitor for mild steel in 1 M hydrochloric acid environment. The synthesized inhibitor (MCNAH) has the ability to impede the corrosion of mild steel in 1 M hydrochloric acid environment at low and high concentrations. The inhibitive efficiency was found to increase with increasing concentration of MCNAH and decrease with increasing time and temperature. The thermodynamic parameters were estimated and discussed. The adsorption of the synthesized inhibitor on the surface of the tested mild steel in the presence of HCl obeyed the Langmuir adsorption isotherm. The relationship between the structure of the new synthesized inhibitor and its inhibitive effects was investigated using theoretical calculations. The experimental and density functional theory (DFT) calculation results are in good agreement. The results clearly show that the inhibition mechanism involves a blocking mechanism of action of the inhibitor.