Introduction: The Need for Effective Corrosion Inhibition in Acidic Environments
Corrosion of metals, especially carbon steel, in acidic solutions is a major concern in various industrial processes, such as cleaning, descaling, and pickling. Carbon steel, while widely used, is particularly vulnerable to corrosion when exposed to acidic environments like hydrochloric acid. This corrosion not only causes damage to the material but also leads to high operational costs in industries where steel is used in acid cleaning and treatment processes. The application of corrosion inhibitors, specifically organic inhibitors, is a key strategy to prevent degradation and extend the life of metallic materials.
Among organic inhibitors, pyrazole derivatives have gained attention due to their ability to efficiently adsorb onto the metal surface, forming a protective layer that reduces corrosion. The current research investigates the corrosion inhibition properties of two newly synthesized bis-pyrazole derivatives, Tetra-Pz-Ortho and Tetra-Pz-Para, which have been tested on carbon steel in a 1 M HCl solution.
Methodology: Experimental Techniques and Computational Analysis
The effectiveness of Tetra-Pz-Ortho and Tetra-Pz-Para as corrosion inhibitors was evaluated using several techniques:
• Weight Loss Method: This traditional method allows the quantification of corrosion rates by measuring the loss of weight of the steel sample before and after exposure to the acidic medium.
• Electrochemical Impedance Spectroscopy (EIS): This technique was used to analyze the resistance of the steel to corrosion in the presence of the inhibitors, providing insights into the charge transfer resistance and double layer capacitance.
• Potentiodynamic Polarization (PDP): This method helped determine the polarization behavior of carbon steel with and without the inhibitors, classifying both compounds as mixed-type inhibitors.
• Scanning Electron Microscopy (SEM): SEM images were taken to observe the surface morphology of carbon steel, showing the reduction in surface roughness when the inhibitors were present.
Additionally, computational chemistry methods, such as Density Functional Theory (DFT) and Molecular Dynamics (MD) simulations, were employed to investigate the molecular interactions between the inhibitors and the steel surface. These calculations helped provide a deeper understanding of the corrosion inhibition mechanisms.
Results: High Efficacy of Tetra-Pz-Ortho and Tetra-Pz-Para
The experimental data showed that both pyrazole derivatives significantly reduced the corrosion of carbon steel in the 1 M HCl solution. At an optimum concentration of 10−3 mol/L and a temperature of 303 K, Tetra-Pz-Ortho achieved a maximum inhibition efficiency of 97.2%, while Tetra-Pz-Para showed an inhibition efficiency of 96.2%. These results indicate that both inhibitors are highly effective, with Tetra-Pz-Ortho performing slightly better.
Key findings include:
• Inhibition Efficiency: Both Tetra-Pz-Ortho and Tetra-Pz-Para exhibited increased inhibition efficiency with higher concentrations of the inhibitors but showed a decrease in effectiveness as the temperature rose.
• Adsorption Study: Both inhibitors adhered to the metal surface following the Langmuir adsorption isotherm, suggesting that the inhibitors are chemically adsorbed onto the steel surface.
• Electrochemical Analysis: The EIS results showed increased charge transfer resistance and reduced double layer capacitance in the presence of the inhibitors, indicating the formation of a protective barrier on the steel surface.
• Surface Morphology: SEM images revealed that the steel surface became significantly smoother with the inhibitors present, confirming the formation of a protective film that prevents corrosion.
Computational Insights: Quantum Chemistry and Simulations
To further understand the mechanism behind the corrosion inhibition, Density Functional Theory (DFT) calculations were performed to analyze the electronic structure and reactivity of Tetra-Pz-Ortho and Tetra-Pz-Para. The computational results were consistent with the experimental findings, supporting the hypothesis that the inhibitors adsorb onto the metal surface through interactions with the electron-rich functional groups in the pyrazole derivatives.
Monte Carlo and Molecular Dynamics simulations provided additional insights into the interfacial interaction between the inhibitors and the steel surface, confirming that the inhibitors adsorb in a way that blocks the corrosive attack of HCl on the metal.
Conclusion: Pyrazole Derivatives as Effective Corrosion Inhibitors
This research demonstrates that both Tetra-Pz-Ortho and Tetra-Pz-Para are highly effective corrosion inhibitors for carbon steel in acidic environments, with Tetra-Pz-Ortho proving to be the most efficient. Their effectiveness is supported by a combination of experimental techniques and computational simulations, revealing the strong protective properties of these newly synthesized pyrazole derivatives.
This study contributes valuable insights into the development of cost-effective and environmentally friendly corrosion inhibitors, which could be widely applied in industries that use carbon steel in corrosive environments.
