Protection of Metals and Physical Chemistry of Surfaces最新文献

The possibilities of return-path laser ellipsometry for monitoring oxidation–reduction processes on metals and alloys in rarefied environments have been studied. A laser automatic ellipsometer has been built based a return-path autocollimation scheme, which makes it possible to remote monitoring of the growth and degree of oxidation of the surface layer on metal samples through the optical window of the vacuum chamber. It has been shown that kinetic return-path ellipsometry makes it possible to record confidently the onset of a new phase formation based on changes in the slope of the experimental ellipsometric nomogram Δ(t)–ψ(t). As an example, laser-ellipsometric studies of low-temperature vacuum oxidation processes of AISI-321 alloy through the optical window of the vacuum chamber of an Auger electron spectrometer have been performed. A combination of kinetic return-path ellipsometry and Auger electron spectroscopy with layer-by-layer etching has been used to show that after the induction period of oxidation, a kink is recorded on the ellipsometric kinetic curve Δ(t)–ψ(t), which is associated with the onset of formation of a thin (40–50 Å) metal–oxide layer of a new oxide phase in the volume due to the exchange reaction of iron oxides with chromium from the alloy and the resulting conversion of iron oxides into spinel (FeCr₂O₄). In this case, the front of this transition shifts closer and closer to the metal–oxide interface, while the formation of low-protective iron oxides becomes increasingly difficult, and they do not have time to reach their maximal thickness.

The adsorption of methane onto an La–BTC metal–organic framework (MOF)was investigated within a pressure range of 0.1−40 MPa at supercritical temperatures of 303, 313, 323, and 333 K. The isotherms of excess adsorption were measured, the adsorption volumes were evaluated, and the isotherms of the total content were calculated, as well as the differential isosteric and initial heats of methane adsorption. Analysis of the obtained results revealed the incompleteness of the gas-adsorption process in the La–BTC MOF in the studied pressure range, which is indicated by the impossibility of fulfilling the condition of equality of the adsorbate and adsorptive densities. The same effect was observed in the previously studied adsorption systems based on other MOFs (Zr–BDC and Al–BTC) and carbon adsorbents. The porous structure of the La–BTC adsorbent was assumed to be the cause of the observed peculiarities of the methane adsorption process.

In this study, hybrid surface composites were fabricated using friction stirring technique to improve the tribological properties of AA6082 aluminum alloy, which has various industrial applications. Micro-scale SiC and n-Al₂O₃ reinforcements were used in the hybrid composites produced. The rotational and travel speeds were chosen as chosen as 1250 rpm and 40 mm min^–1, respectively. After the double pass production, it was determined that the homogeneous particle distribution in the surface region lost this homogeneity in the lower regions of the surface. The hardness of the hybrid surface composites was found to be approximately 44.2% higher than AA6082 aluminum alloy. It was determined that the wear resistance of SiC/n-Al₂O₃ reinforced hybrid surface composites produced by friction stir processing was up to 68.5% higher than non-reinforced AA6082 alloy.

This study aimed to investigate the corrosion inhibition behavior of zeolitic materials on aluminum in 1 M HCl solution. This investigation used electrochemical methods (polarization curves and electrochemical impedance spectroscopy). Polarization curves indicate that the inhibition mechanism primarily acts as a mixed-type inhibitor, with the corrosion rate of aluminum in 1 M HCl reduced by 99.57% at an inhibitor concentration of 100 ppm. Electrochemical impedance diagrams demonstrate that inhibition occurs through a charge transfer process on a heterogeneous surface across all tested zeolite concentrations. Scanning electron microscopy micrographs revealed that the formed film effectively blocked acid attack through physical and chemical adsorption on the aluminum surface.

The corrosion and inhibition processes of cold rolled steel was investigated by gravimetric weight loss measurement in 1 M HCl solution, at a temperature range of 303–333 K, in the absence and presence of potassium iodide (KI) inorganic halide salt (8.67 × 10^–3–2.17 × 10^–2 M), formaldehyde (FA: CH₂O) organic surfactant (1.00 × 10^–3 M), and KI (2.17 × 10^–2 M)–FA (1.00 × 10^–3 M) inhibitors mixture. The exposed surfaces of steel samples were inspected by scanning electron microscopy (SEM) and Raman micro-spectroscopy techniques. The inhibition efficiency (IE(%)) increased with KI concentration and temperature suggesting that the KI inhibitor efficiencies are temperature-dependent. The adsorption of KI on steel surface was found to obey Langmuir isotherm. The calculated adsorption free energy ((Delta G_{{{text{ads}}}}^{^circ })) is included between ‒20 and −40 kJ mol^–1 indicating that the adsorption of KI inhibitor is a combination of both physisorption and chemisorption. It was also found that the FA inhibitor efficiency decreased with the increase of temperature, and the calculated value of activation energy (({{E}_{{text{a}}}})) demonstrated that the mechanism of FA adsorption is physical adsorption. It was further observed that there is a synergism for FA mixing with KI, and all calculated synergism parameters are high than unity for the entire temperature range studied. It more showed that SEM and Raman microanalyses confirmed the adsorption mechanisms of KI, FA, and FA + KI on the steel surfaces. Therefore, the more probable mechanisms of corrosion inhibition were proposed.

This study deals with the corrosion inhibition nature of a terpolymer of methyl methacrylate (MMA), vinyl benzoyl chloride (VBC), and N-2-methyl-4-nitrophenyl maleimide (MI) on carbon steel in a 1 M HCl solution. The genesis of the study is based on organic terpolymers used as corrosion inhibitors reiterating the synergistic effects on corrosion inhibition contributed by different monomers and their adsorption behaviors on the metal surface. The polymer termed P(MMA–VBC–MI) was synthesized via solution radical polymerization in varying molar ratios of MMA/VBC of 60 : 10, 50 : 20, 40 : 30, with MI being constant at 30%. Some of the characterization methods used were FTIR for terpolymer structure elucidation, thermal analyses (TGA, DTG, and DSC) for thermal stability studies, and electrochemical experiments, such as potentiodynamic polarization and EIS, for inhibition studies. The primary results showed that the terpolymer with 30% VBC content had greater thermal stability and corrosion resistance compared to pure polymethyl methacrylate (PMMA) because of the decrease in the mobility of polymer chains, in addition to the formation of a passive protective layer on the steel surface. EIS and polarization results indicated that terpolymer Ter3 with an MMA/VBC ratio of 40 : 30 exhibited the highest inhibition efficiency, and the adsorption behavior of this terpolymer followed the Langmuir isotherm model (adsorption free energy between –34.48 and –39.35 kJ/mol), suggesting physical along with chemical adsorption phenomena. These findings underscore the significance of organic terpolymers as biocompatible and nontoxic alternatives to conventional inhibitors like chromates, providing environmentally friendly alternatives for corrosion protection of carbon steel in acidic media. The findings of this study can result in the creation of new inhibitor materials for industrial applications, particularly in oil and gas industries, and in furthering the understanding of corrosion inhibition mechanisms.

With the acceleration of urban construction in China, subway lines across waters (rivers, lakes and oceans) have been built by many water-containing cities to meet the development needs. This paper is targeted at this issue, and relevant literature is comprehensively analyzed, and the current situation of cross-water subway construction is arranged, and it is found that there are many complex technical problems in such subway lines, among which the stray current problem is the key. Due to the special environment, the stray current distribution and corrosion characteristics of cross-water subway lines are significantly affected. Firstly, the distribution law of stray current in cross-water environment is deeply explored. Secondly, the corrosion characteristics of stray current in cross-water environment are studied. Finally, the harm and protection measures of stray current to buried pipelines in cross-water subway lines are introduced, and a theoretical reference is provided for the safe operation and maintenance of cross-water subway system.

Climate change poses a threat to the water security by altering the precipitation patterns and other weather variables, which affect stream flow and freshwater availability. In this study, a soil and water assessment tool was used for the scarcity of blue and green water for future periods for sustainable management of freshwater resources away from lead pollution. Indeed, the presence of Pb²⁺ is an environmental problem and we have explored the use of natural phosphates (NP) as adsorbents for its elimination. The adsorbent NP was characterized by FTIR spectroscopy, scanning electron microscopy (SEM) and BET analysis. Batch adsorption experiments were performed to examine the effects of physical parameters namely the contact time, pH, stirring speed, temperature, adsorbent dose and initial Pb²⁺ concentration on the uptake capacity. Different models were used to fit the experimental data and to evaluate the kinetics, isotherms and thermodynamics of the Pb²⁺ adsorption. A high adsorption capacity of 66.66 mg/g was reached at 25°C and pH 6 and follows the Langmuir isotherm with a pseudo-second order kinetic. The adsorption is spontaneous and endothermic, indicating a structural exchange between NP and Pb²⁺ ions. Such results suggest that NP is a promising adsorbent for Pb²⁺ removal from wastewater.

Green self-assembled monolayers (SAMs) were formed on the copper surface using Passiflora edulis Sims peel extract (PESPE). The functional groups of active constituents in PESPE and their self-assembly behavior were characterized by Fourier-transform infrared (FTIR) spectroscopy, UV-visible spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The effects of PESPE-SAMs on the surface roughness and hydrophobicity of copper were investigated utilizing atomic force microscopy (AFM) and a contact angle goniometer. The corrosion protection performance of PESPE-SAMs for copper in a 3.5% NaCl solution was evaluated through electrochemical measurements and an analysis of the corrosion morphology. Results indicate that functional groups such as C–O, C=O, and C=N within PESPE are adsorbed onto the copper substrate, forming a hydrophobic protective film (i.e., PESPE-SAMs). Notably, the corrosion rate of copper is significantly reduced, with a corrosion protection efficiency of approximately 86.7%. Pitting and flocculent corrosion products on the copper surface are almost entirely inhibited. Therefore, PESPE serves as an effective and renewable agent for SAMs formation, demonstrating extensive potential applications.