Versatile 4, 6-dimethyl-2-mercaptopyrimidine based ionic liquids as high-performance corrosion inhibitors and lubricants

1-Butyl-3-methylimidazolium methane sulfonate ionic liquid corrosion inhibitor for mild steel alloy: Experimental, optimization and theoretical studies

The current research reports the performance of 1-butyl-3-methylimidazolium methane sulfonate ([C4MIM][OMs](IL)) as effective corrosion inhibitor for mild steel in 1 M H2SO4 electrolyte. For proper evaluation, weight loss, electrochemical study, theoretical modeling and optimization techniques were used. Weight loss and electrochemical methods shows that the inhibition performance of [C4MIM][OMs] on the metal surface strengthens as the concentration increases. Maximum inhibition efficiency of 85.71%, 92.5% and 91.1% at 0.8 g L-1 concentration of [C4MIM][OMs] were obtained from the weight loss, polarization and impedance studies, respectively. In addition, response surface methodology (RSM) a statistical tool was used for modeling and optimization of the empirical data. The RSM model validates the empirical findings. Also, DFT/MD-simulation investigations evidenced that [C4MIM][OMs] forms a barrier film on the mild steel surface. The result shows that the synthesized [C4MIM][OMs] could open up opportunities in corrosion and materials protection for sustainability.

Falcaria vulgaris leaves extract as an eco-friendly corrosion inhibitor for mild steel in hydrochloric acid media

Undoubtedly, metal corrosion is one of the most challenging problems faced by industries. Introducing corrosion inhibitors is a reasonable approach to protecting the metal surface. Due to environmental concerns and the toxicity of industrial organic corrosion inhibitors, researchers are continually exploring acceptable replacements. The current study focused on the application of Falcaria Vulgaris (FV) leaves extract to mitigate mild steel (MS) corrosion in a 1 M HCl environment. The polarization findings demonstrated that the corrosion current density decreased from 264.0 µA/cm² (for the sample submerged in the blank solution) to 20.4 µA/cm² when the optimal concentration of 800 ppm of FV leaves extract was added to the acid solution. Electrochemical impedance spectroscopy (EIS) analysis revealed an inhibition efficiency of 91.3% at this concentration after 6 h of immersion. It was determined by analyzing several adsorption isotherms that this corrosion inhibitor obeys the Frumkin isotherm. AFM, FE-SEM, and GIXRD surface analyses also supported the findings that adding FV leaves extract can reduce metal damage by adsorption on the metal surface.

The superior lubricating performance and unique mechanism of oil-soluble protic ionic liquids with short alkyl chains

HYPOTHESIS

Ionic liquids (ILs), as lubricant additives, can greatly improve the lubricating behavior of the frictional interfaces. However, it is urgent to explore ILs with good oil solubility in nonpolar oils, and it is necessary to further study and verify the lubrication mechanism of ILs from the perspective of alkyl chain length.

EXPERIMENTS

Five protic ILs (PILs) with varying alkyl chain lengths were synthesized by proton transfer method. As additives in PAO oil, their tribological properties were investigated on SRV-V tester. Through molecular dynamics simulation, the adsorption behavior of PILs at the frictional interface was illustrated.

FINDINGS

The tribological properties of base oil could be significantly improved by adding PIL additives, but interestingly, PILs with short-chain anions showed better lubricating performance, which contradicted most of the early findings. Further analyses revealed that PILs achieved effective lubrication by the tribochemical interaction between anions and frictional interface, and the formation of cationic protective layer. However, PILs with shorter-chain anions form a denser protective layer that can better support the interfacial anions to participate in tribochemical reactions and thus abnormally exhibit superior lubricating performance than those with longer-chain anions.

Improving the sustainability of biodiesel by using imidazolium-based ionic liquid

Corrosion of biodiesel-filled fuel tanks has become a major problem in the use of biodiesel as a new green energy source. The ionic liquid 1-Hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [C₁₀H₁₉N₂]⁺[C₂F₆NO₄S₂]⁻ was used to control corrosion of C-steel in non-edible biodiesel to resolve this problem. The anti-corrosion and antioxidant properties of the [C₁₀H₁₉N₂]⁺[C₂F₆NO₄S₂]⁻ were characterized using weight loss, electrochemical impedance spectroscopy, total acid number measurements beside SEM and EDX analysis. The findings show that [C₁₀H₁₉N₂]⁺[C₂F₆NO₄S₂]⁻ plays an important role in preventing C-steel corrosion in biodiesel with an efficiency close to 99 percent. The adsorption capability and antioxidant properties of [C₁₀H₁₉N₂]⁺[C₂F₆NO₄S₂]⁻ are the major contributors to the ionic liquid's anti-corrosion properties. We anticipate that this work will help to sustainable expand the use of biodiesel as a renewable energy source.

Synthesis, Characterization, and Computational Chemical Study of Aliphatic Tricationic Surfactants as Corrosion Inhibitors for Metallic Equipment in Oil Fields

Aliphatic tricationic surfactants were prepared by the esterification reaction, followed by a quaternization reaction to protect oil well facilities from corrosion problems. Microelemental analysis and Fourier transform infrared and ¹H NMR spectroscopic techniques were performed to explore the obtained motifs. The performance of these amphiphiles as inhibitors for metallic S90 steel corrosion in formation water was investigated through electrochemical tests (potentiodynamic polarization and electrochemical impedance spectroscopy). The results revealed significant inhibition effectiveness improvement with increasing concentrations of these amphiphiles. Its maximum inhibition efficiency reaches 93.07% at 250 ppm for the compound (AED). Potentiodynamic polarization graphs demonstrated that tricationic amphiphiles behave as mixed-type inhibitors. In addition, the adsorption of the tricationic surfactant at the S90 steel surface followed Langmuir isotherm. Atomic force microscopy revealed that a protective layer formed at the surface of S90 steel caused the inhibition of corrosion. During the inhibition procedure of S90 steel corrosion, theoretical research has been performed to validate electrochemical experiments and to clearly demonstrate the mechanism of these amphiphiles. Finally, quantum chemical calculations were calculated to achieve the justification for the obtained empirical results.

Synergistic effect of potassium iodide and sodium dodecyl sulfonate on the corrosion inhibition of carbon steel in HCl medium: a combined experimental and theoretical investigation

Carbon steel is an important industrial material, but it usually suffers from serious corrosion in the service environment. Using corrosion inhibitors is an effective approach to mitigate corrosion. The synergistic inhibition behavior of sodium dodecyl sulfonate (SDS) and potassium iodide (KI) on carbon steel corrosion in hydrochloric acid medium was investigated by electrochemical test, surface morphology analysis, and molecular simulation approaches. Results show that the corrosion inhibition performance is significantly enhanced after the two substances are compounded, and the inhibition efficiency can reach approximately 96% at small doses. The Tafel polarization curves suggest that the mixtures can be classified as anodic corrosion inhibitors. Impedance tests indicate that the inhibitor molecules are adsorbed on the steel surface, resulting in an increase of charge transfer resistance but a decrease of electric double layer capacitance. The adsorption process follows the Langmuir adsorption isotherm. Molecular simulation calculations further reveal the active sites of SDS and the stabilizing effect that I⁻ plays in the inhibition process. The present research offers an economic, environmentally friendly and efficient measure of corrosion control, and provides theoretical guidance for the efficient use of carbon steels and the development of novel corrosion inhibitors.

Carbon steel is an important industrial material, but it usually suffers from serious corrosion in the service environment.

Ionic liquid lubricants: when chemistry meets tribology

Ionic liquids (ILs) have emerged as potential lubricants in 2001. Subsequently, there has been tremendous research interest in ILs from the tribology society since their discovery as novel synthetic lubricating materials. This also expands the research area of ILs. Consistent with the requirement of searching for alternative and eco-friendly lubricants, IL lubrication will experience further development in the coming years. Herein, we review the research progress of IL lubricants. Generally, the tribological properties of IL lubricants as lubricating oils, additives and thin films are reviewed in detail and their lubrication mechanisms discussed. Considering their actual applications, the flexible design of ILs allows the synthesis of task-specific and tribologically interesting ILs to overcome the drawbacks of the application of ILs, such as high cost, poor compatibility with traditional oils, thermal oxidization and corrosion. Nowadays, increasing research is focused on halogen-free ILs, green ILs, synthesis-free ILs and functional ILs. In addition to their macroscopic properties, the nanoscopic performance of ILs on a small scale and in small gaps is also important in revealing their tribological mechanisms. It has been shown that when sliding surfaces are compressed, in comparison with a less polar molecular lubricant, ion pairs resist "squeeze out" due to the strong interaction between the ions of ILs and oppositely charged surfaces, resulting in a film that remains in place at higher shear forces. Thus, the lubricity of ILs can be externally controlled in situ by applying electric potentials. In summary, ILs demonstrate sufficient design versatility as a type of model lubricant for meeting the requirements of mechanical engineering. Accordingly, their perspectives and future development are discussed in this review.