In the present work, new compounds, namely 2-fluoro phenyl-2,5-dithiohydrazodicarbonamide (2FPDC) and 4-fluoro phenyl-2,5-dithiohydrazodicarbonamide (4FPDC), were successfully synthesized and examined as corrosion inhibitors for mild steel in 1 M HCl. The molecular structures were characterized by Fourier transform infrared spectroscopy (FT-IR) and 1 H, 13 C nuclear magnetic resonance (NMR). A scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX), and atomic force microscope (AFM) were conducted to identify the surface morphology of mild steel in the absence and existence of a corrosion inhibitor. Several electrochemical techniques have been conducted to evaluate inhibitor efficiency. The influence of immersion time on the efficiency of inhibitors was also investigated. The electrochemical results showed that both compounds appeared to be mixed type. However, 4FPDC is slightly more efficient than 2FPDC (97.3% compared with 96.5% at 1 × 10 −2 M and an immersion time of 5 h). The resistance polarization for inhibitors was found to obey an order of 4FPDC > 2FPDC. The Langmuir isotherm system revealed the best match, and the type of adsorption was physisorption and chemisorption in both compounds. SEM and EDX results have confirmed the presence of particles of inhibitor on the metal surface. A smooth surface was observed in the presence of inhibitors approved by AFM. Quantum chemical results showed that the adsorption of molecules of inhibitor takes place predominantly through protonated structures, and strongly agreed with experimental results. The results reveal that excellent inhibition efficiency was attained even in aggressive conditions, and they can be viewed as novel corrosion inhibitors for mild steel with excellent protection.
Keywords
Materials and Experimental Methods
MaterialsA mild steel rod was purchased from a local market with a chemical composition as follows: (Wt.%): 0.18 C,
The corrosion process can be seen as a widespread phenomenon, which is both pervasive and unstoppable. This is an undesirable phenomenon that reduces the life of materials and takes away their beauty. Potentiodynamic and electrochemical impedance tests are used to explore the corrosion inhibition abilities of a room temperature columnar liquid crystalline perylene bisimide (PBIO10) on mild steel (MS) samples in 1 M HCl. The inhibitor PBIO10 was demonstrated to be an outstanding corrosion inhibitor, with a maximum inhibition efficiency of 76%. In light of potentiometric polarization results, corrosion inhibition was achieved as the inhibitor getting adsorbed on the metal, and they fit into the category of anodic inhibitors. The protective layer was examined from SEM to confirm the protective coating generated on the MS surface. The increase in contact angle confirms the formation of a uniform layer on the MS surface. Analysis of the optical textures observed in POM, the nature of the mesophase under examination to columnar rectangular (Colr) phase. From the TGA, it was found that PBIO10 exhibits higher thermal stability u to 370 ℃. The density functional theory (DFT) and Monte Carlo simulation approach were used to investigate the relationship between molecular structure and inhibitory efficacy. The thermal behavior of PBIO10 was investigated by polarizing optical microscopy (POM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and X-ray diffraction (XRD) studies. The phase transition from crystal to LC phase was at first examined with the help of POM observation.
Graphical Abstract
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