article · Scientific Reports
This research evaluates two newly synthesised bi-pyrazole derivatives, named Tetra-Pz-Ortho and Tetra-Pz-Para, as corrosion inhibitors for carbon steel exposed to a hydrochloric acid solution. Using weight loss measurements alongside electrochemical impedance spectroscopy and potentiodynamic polarisation, the tests showed that both compounds act as mixed-type inhibitors. At an optimal concentration of 0.001 moles per litre and a temperature of 303 Kelvin, Tetra-Pz-Ortho achieved a maximum inhibition efficiency of 97.2 percent, slightly outperforming Tetra-Pz-Para at 96.2 percent. The protective performance increased with higher concentrations but declined at elevated temperatures. Microscopic and elemental surface analyses confirmed that the molecules chemically adsorb onto the metal surface following the Langmuir adsorption isotherm, smoothing surface roughness. Computational quantum chemistry and molecular dynamic simulations aligned with these experimental findings, establishing that Tetra-Pz-Ortho is the more effective protective compound.
Carbon steel degrades rapidly in harsh acidic environments, causing structural failures and costly equipment replacements. Identifying highly effective chemical compounds that coat and protect steel surfaces helps reduce metal degradation. Demonstrating that these newly synthesised pyrazole molecules block over 96 percent of corrosion offers clear design principles for formulating more resilient protective treatments in acid-exposed settings.
The findings could enable the development of high-performance chemical additives to protect carbon steel equipment used in acidic industrial processes. Potential users include manufacturers of industrial cleaning fluids, pickling solutions, and anti-corrosion chemical formulations. This work represents early-stage laboratory and computational research, requiring further applied testing under real-world operating conditions before commercial development can proceed.
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In the current investigation, the efficiency inhibition of two newly synthesized bi-pyrazole derivatives, namely 2,3-bis[(bis((1 H-pyrazol-1-yl) methyl) amino)] pyridine (Tetra-Pz-Ortho) and 1,4-bis[(bis((1 H-pyrazol-1-yl) methyl) amino)] benzene (Tetra-Pz-Para) for corrosion of carbon steel (C&S) in 1 M HCl medium was evaluated. A Comparative study of inhibitor effect of Tetra-Pz-Ortho and Tetra-Pz-Para was conducted first using weight loss method and EIS (Electrochemical Impedance Spectroscopy) and PDP (Potentiodynamic Polarisation) techniques. Tetra-Pz-Ortho and Tetra-Pz-Para had a maximum inhibition efficacy of 97.2% and 96.2% respectively at optimum concentration 10−3mol/L and temperature 303 K, according to the data, suggesting that they are both effective inhibitors. The inhibition effectiveness of Tetra-Pz-Ortho and Tetra-Pz-Para increases significantly with higher concentration but decreases as temperature rises. The adsorption study demonstrated that the two molecules tested follow the Langmuir adsorption isotherm and chemically adsorbed on the metallic surface. The polarization methods showed that both compounds Tetra-Pz-Ortho and Tetra-Pz-Para were classified as mixed inhibitors. Based on the electrochemical impedance technique, the addition of the two inhibitors increased the charge transfer resistance and decreased the double layer capacity. In addition, the scanning electron microscopy (SEM) showed that the surface roughness of the C&S was considerably reduced in the presence of both Tetra-Pz-Ortho and Tetra-Pz-Para compared to its roughness without the inhibitors, indicated that the two inhibitors are effectively absorbed onto the carbon steel surface. These results were supported by elemental analysis of the metal/solution interface using X-ray photoelectron spectroscopy (XPS), for the two molecules tested. All studies demonstrated that the compound Tetra-Pz-Ortho is the most effective inhibitor. The DFT calculations and Monte Carlo/Molecular dynamic (MC/MD) simulations were treated and discussed for both compounds Tetra-Pz-Ortho and Tetra-Pz-Para in order to explain their interfacial approach and compared them to experimental results. The computational results of quantum chemistry were in agreement with those acquired by experimental methods.
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DOI: 10.1038/s41598-025-87564-w
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