Experimental study of electromechanical measurement, surface analysis and corrosion inhibition of mild steel in 1M HCL by Schiff’s bases (SBs)

Potentiodynamic polarization measurements indicate that SBs acts as mixed type corrosion inhibitors. the morphology of the mild steel surface is investigated by scanning electron microscopy (SEM) and the surface composition was evaluated using energy-dispersive X-ray Spectroscopy (EDX) to show the presence of SBs on the mild steel surface in 1M HCL. The present study, three Schiff’s bases (SBs) namely 2 (2-hydroxybenzylideneamino) heptanedioic acids, 2 (4-dimethylamino benzlideamino) heptanedioic acids and 2 (4hydroxy-3-methoxybenzylideneamino) heptanedioic acids were synthesized. Using weight loss, potentiodynamic polarization and electromechanical impedance spectroscopy (EIS) techniques for corrosion inhibition properties on mild steel in 1M HCL has been investigated. The adsorption of SBs on the mild steel surface contains Langmuir adsorption isotherm. Here kinetic and thermodynamic parameters also determined to describe the mechanism of adsorption in relevance. The main object of this presentation is experimental study of the inhibiting action of synthesized Schiff’s bases of aldehydes containing nitrogen, oxygen and aromatic rings and Glutamic acid.

Inhibition Evaluation of 5-(4-(1H-pyrrol-1-yl)phenyl)-2-mercapto-1,3,4-oxadiazole for the Corrosion of Mild Steel in an Acidic Environment: Thermodynamic and DFT Aspects

In this investigation, an oxadiazole namely 5-(4-(1H-pyrrol-1-yl)phenyl)-2-mercapto-1,3,4-oxadiazole (PMO), was synthesized and explored as an inhibitor against the corrosion of mild steel in 1.0 M hydrochloric acid environment at various solution temperature 303-333 K. gravimetric, and microscopic techniques, namely, weight loss (WL), and scanning electron microscopy (SEM), have been used to evaluate the inhibitive performance of the tested PMO. The results of the WL method displayed that the inhibition efficiency (%IE) was found to increase with the inhibitor concentration, while it reduced with increasing temperature. Furthermore, the WL results reveal that PMO inhibits corrosion display an IE of 95% at the highest concentration of 0.005 M. The SEM images of the mild steel surface coupon after adding PMO revealed a wide coverage of PMO molecules on the mild steel surface. Hence, the high inhibiting efficiency acquired by the tested inhibitor was explained by the strong adsorption of PMO molecules on the surface of mild steel. A protective layer has been constructed and it separating the mild steel surface from the hydrochloric acid solution, and such adsorption was found to obey Langmuir adsorption isotherm. Moreover, the thermodynamic parameters suggested that the adsorption nature of PMO molecules on the coupon surface was chemo-physisorption. Quantum chemical calculations were conducted by density functional theory (DFT) which help correlate the methodological findings with the theoretical investigations. The mechanisms of PMO molecules as corrosion inhibitor for mild steel surface in the corrosive environment was also discussed.

Insights into Corrosion Inhibition Behavior of a 5-Mercapto-1, 2, 4-Triazole Derivative for Mild Steel in Hydrochloric Acid Solution: Experimental and DFT Studies

A triazole heterocyclic compound namely 3-(4-ethyl-5-mercapto-1, 2, 4-triazol-3-yl)-1-phenylpropanone (EMTP) was examined for its corrosion protection of mild steel (MS) against 1 M hydrochloric acid medium using gravimetric techniques. EMTP exhibited excellent corrosion protection performance at low and high concentrations towards MS in HCl solution. Comparison of corrosion protection performance of EMTP and its parent triazole and temperature effects of on inhibition efficacy were also studied. EMTP has potential corrosion inhibitor for mild steel in 1.0 M hydrochloric acid solution with the highest protection efficacy of 97% at 303 K. The weight loss findings implied that EMTP protects the metal surface corrosion through the creation of a protective layer at the surface mild steel–corrosive solution interface. The inhibitive efficacy increases with the increase of inhibitor concentration and decreases with increased temperature. The adsorption of EMTP on the surface of MS follows Langmuir’s adsorption isotherm process. DFT method was conducted on EMTP molecule to calculate the quantum chemical parameters and to determine the relationship between the molecular structure of EMTP and protection performance. The molecular parameters, such as energy gap and frontier molecular orbital (highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO)), and the absolute electronegativity (χ) value from inhibitor molecules to unoccupied d-orbital of iron atoms on the mild steel surface were also determined and correlated with protection efficiency. The theoretical findings revealed that the protection performance of EMTP increased with the increase in HOMO energy, and the nitrogen, oxygen and sulfur atoms are most probable positions for bonding through giving electrons to the d-orbital of iron atoms on the mild steel surface.

Inhibition of Mild Steel Corrosion by 4-benzyl-1-(4-oxo-4-phenylbutanoyl)thiosemicarbazide: Gravimetrical, Adsorption and Theoretical Studies

Gravimetric measurements were applied to study the inhibitory effect of 4-benzyl-1-(4-oxo-4-phenylbutanoyl)thiosemicarbazide (BOT) on the corrosion of mild steel in 1.0 M HCl. BOT has a good inhibitory efficacy of 92.5 percent at 500 ppm, according to weight loss results. The effect of inhibitor concentration on the mild corrosion behavior of steel was investigated and it was discovered that the higher the inhibitor concentration, the higher the damping efficiency. The results confirm that BOT is an effective corrosion inhibitor for mild steel in the presence of 1.0 M HCl. Furthermore, the higher protection efficiency with increasing temperature and the free energy value showed that BOT molecules participate in both chemisorption (coordination bonds between the active sites of BOT molecules and d-orbital of iron atoms) and physisorption (through the physical interactions on the mild steel surface). The adsorption mechanism on the mild steel surface obeys the Langmuir adsorption isotherm model. Quantum chemical calculations based on the DFT calculations were conducted on BOT. DFT calculations indicated that the protective efficacy of the tested inhibitor increased with the increase in energy of HOMO. The theoretical findings revealed that the broadly stretched linked functional groups (carbonyl and thionyl) and heteroatoms (sulfur, nitrogen and oxygen) in the structure of tested inhibitor molecules are responsible for the significant inhibitive performance, due to possible bonding with Fe atoms on the mild steel surface by donating electrons to the d-orbitals of Fe atoms. Both experimental and theoretical findings in the current investigation are in excellent harmony.