An efficient green ionic liquid for the corrosion inhibition of reinforcement steel in neutral and alkaline highly saline simulated concrete pore solutions

Passivation performance of Nb microalloyed rebar in concrete carbonation environments with different pH

In this study, XPS sputtering depth, SEM and electrochemical tests (CV, EIS, M-S, i-t, DPP) were used to study the structural composition and formation mechanism of surface passive film of Nb microalloyed rebar in SCPS with different pH. The results showed that after passivation for 10 d in SCPS with different pH, compared with CS rebar, the stability and compactness of surface passive film of 34Nb rebar gradually increased with the decreases of pH. Firstly, with the decreases of pH, the outer layer of surface passive film of 34Nb rebar was composed of Fe oxides and Fe hydroxides, and the inner layer was composed of Fe oxides and Nb oxides, thus increasing the mass ratio of Fe3+/Fe2+ and Nb2O5/(NbO2 + NbO). Secondly, with the decreases of pH, the addition of Nb promoted the formation of Fe oxides in 34Nb rebar, obtaining the excellent Rct, Ecorr and Ep. Finally, with the decreases of pH, the addition of Nb promoted the enrichment of Nb oxides in 34Nb rebar, inhibiting the degradation of Fe oxides, and the passive film exhibited the P-N type semiconductor, thus significantly decreasing the carrier density and enhancing the passivation rate of 34Nb rebar.

Adsorption and mitigation impact of the monosodium glutamate (C5H8NO4Na) bio-molecules on the steel rebar corrosion in the chloride-contaminated simulated concrete pore solution

Corrosion has caused significant annual costs for building construction and civil architectural designs. In this study, Monosodium glutamate (GLU) was proposed as a potential candidate for long-lasting corrosion inhibition to slow down the rate of corrosion in the concrete pore environment. In this regard, the electrochemical and morphological properties of the various GLU concentrated systems between 1 to 5 wt% in the simulated concrete pore solution media were investigated. According to the EIS results, adding 4 wt% of GLU could reduce the mild steel corrosion process by 86% through a mixed inhibition mechanism. Also, the polarization records represented that the samples' corrosion current density was diminished to 0.169 µA cm^-2 after the addition of 4 wt% GLU into the harsh environment. Using the FE-SEM method, the growth of the GLU layer over the metal substrate was demonstrated. The results of spectroscopic methods, i.e., Raman and GIXRD, demonstrated that GLU molecules were successfully adsorbed over the surface of the metal. Contact angle test outcomes showed that by increasing the GLU concentration to its optimum level (4 wt%), the surface hydrophobicity was dramatically raised to 62°.

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.

Ionic liquid as an effective green inhibitor for acid corrosion of aluminum composite: experimental and theoretical considerations

Results of anticorrosive performance of ionic liquid 1-methyl-1-propyl-piperidinium bromide (MPPB) on corrosion of 6061Al-10vol% SiC composite (Al-MMC) in 0.05 M HCl solution. Electrochemical techniques were adopted to study corrosion and corrosion inhibition rates. Experiments were conducted in the temperature range of 308–323 K by varying concentrations of MPPB. Conditions were standardized to accomplish maximum inhibition efficiency. Kinetic parameters were evaluated. Results were fitted into various adsorption isotherm models and they fitted best into the Langmuir adsorption isotherm. Using data from adsorption isotherms, thermodynamic parameters were calculated. The surface morphology was examined by energy-dispersive X-ray spectroscopy (EDAX), atomic force microscope (AFM), and scanning electron microscope (SEM). FTIR–spectra and X-ray diffraction (XRD) studies were performed to reaffirm the adsorption of MPPB. Adsorption of the inhibitor and mechanistic aspects of corrosion inhibition were supported and supplemented by quantum chemical calculations using density functional theory (DFT). The investigation revealed that percentage inhibition efficiency (% IE) improved with the increase in the concentration of MPPB, while it decreased with a rise in temperature. Maximum efficiency of 60% was observed with 400 ppm MPPB at 308 K. MPPB acted as a mixed inhibitor, obeyed the Langmuir adsorption model, and the mode of adsorption was physisorption. Quantum chemical calculations validated the results of the adsorption study.

Graphical abstract

Impact of Prolonged Exposure to Sour Service on the Mechanical Properties and Corrosion Mechanism of NACE Carbon Steel Material Used in Wet Sour Gas Multiphase Pipeline

The oil and gas industry is involved with severe corrosive/sour environmental conditions due to H2S, CO2, and moisture content. The National Association of Corrosion Engineers (NACE) has developed standards to enable users to select suitable materials for given sour conditions which utilize laboratory testing. A failed piping sample (API-5L-X65) was removed from a pipeline after 15 years of service. Optical microscopy was used to compare the microstructure of the corroded sample near the exposed surface to both the service environment, and further away from it. Moreover, pitted samples were analyzed using a scanning electron microscope coupled with energy dispersive X-ray (SEM/EDS) to understand the deposits’ morphology. Furthermore, XPS analysis proves the presence of a significant content of sulfur compound. Additionally, the mechanical properties of both corroded and non-corroded samples were evaluated and compared. Micro-hardness was carried out on the cross-section of the removed sample to understand any evident hardness variation from the inner diameter (ID) to the outer diameter (OD) of the piping. All the results suggest that prolonged service exposure has resulted in the development of micro defects, resulting in the reduction of strength and impact toughness, and the reduction in the hardness at the exposed surface of the corroded piping. Understanding the corrosion mechanism of pipelines exposed to sour media in the long-term helps in repair/replacement planning and extending the usable design life of the material, and paving the way for the oil and gas industry to develop additional ways to monitor the changes in the critical materials’ properties when exposed to sour service.

Sonocatalytic recovery of ceria from graphite and inhibition of graphite erosion by ionic liquid based platinum nanocatalyst

Use of ultrasound as an intensified non-destructive decontamination technique for processing graphite limits its reusability beyond a few number of decontamination cycles due to the exfoliation of graphite due to cavitation effects. The current work establishes that the use of platinum nanoparticles in the leachant reduces the erosion of graphite substrate due to cavitation. It presents an improved way of sonochemical recovery of ceria using a mixture of nitric acid, formic acid and hydrazinium nitrate in the presence of platinum nanoparticles and ionic liquid. The platinum nanoparticles catalyst in ionic liquid prevented the generation of the carbon residue due to the combined effect of denitration and reduced sonication. The presence of the catalyst showed a fivefold increase in dissolution kinetics of ceria as well as absence of graphite erosion, facilitating better chances of graphite recycling than the decontamination without the catalyst. The catalytic approach offers a better recycle strategy for graphite with reduced exfoliation and NOx generation due to denitration, making it a more sustainable decontamination process. Since ceria is used as a surrogate for plutonium oxide, the results can be extended to decontaminate such deposits clearly establishing the utility of the presented results in the nuclear industry.

Alleviation of Iron Corrosion in Chloride Solution by N,N′-bis[2-Methoxynaphthylidene]amino]oxamide as a Corrosion Inhibitor

The alleviation of iron corrosion in 3.5% NaCl sodium chloride solution using N,N′-bis[2-methoxynaphthylidene]amino]oxamide (MAO) as a corrosion inhibitor has been reported. The work was achieved using various investigation techniques. Potentiodynamic cyclic polarization (PCP) displayed a powerful inhibition for the corrosion via reducing the iron’s cathodic and anodic reactions. This was reflected in reduced corrosion currents and increased polarization resistances in the presence and upon the increase of MAO concentration. The electrochemical impedance spectroscopy results indicated that MAO molecules provoke the corrosion resistance via increasing polarization resistance. The power of MAO on decreasing pitting attack was also investigated through measuring the change of current with time at −0.475 V(Ag/AgCl). Scanning electron microscopy images were taken of the surface after the current–time measurements were performed in the absence and presence of MAO. The current-time experiments indicated that MAO highly mitigates the corrosion of iron. The energy dispersive X-ray analyzer reported the products found on the tested surfaces. The effect of extending the exposure time from 1 h to 48 h was also tested and was found to alleviate the corrosion of iron, whether MAO molecules are absent or present.