Materials and Corrosion-werkstoffe Und Korrosion最新文献

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Comparison of E_pit vs. I_corr between the investigated HEAs and several stainless-steel samples in a 3.5 wt.% NaCl solution. The results show that some HEAs (such as Al_0.6CrFeNi_2.4 or CrFeNi₂) exhibit corrosion resistance similar to (or even superior to) stainless steel.

More detailed information can be found in: Jinqing Liang, Wei Wang, Zhenghang Cao, Jianwen Guo, Zhenzhong Sun, Yang Hai, Corrosion Resistance and Mechanism of High-Entropy Alloys: A Review, Materials and Corrosion 2024, 75, 424.

The main cause of corrosion of reinforcing steel, especially in infrastructure structures, is the penetration of chlorides, which can lead to high corrosion rates at the reinforcement steel. A frequently used accelerated test method to evaluate the chloride penetration resistance of concrete and mortars is the rapid chloride migration (RCM) test. The test was initially developed for ordinary Portland cement (OPC) based materials and involves spraying an indicator solution onto split test specimens to determine the penetration depth of the chloride ions. The pore solution compositions of new types of binders differ from OPC-based materials, which can affect the reaction of the indicator solution. To investigate the suitability of the RCM test, the chloride content in the depth of the color change was determined in mortars made from different types of novel binders. The results show that the test provides reliable results for the binder types with partial replacement of OPC by supplementary cementitious materials. For binder types without OPC, there is a deviation in the migration coefficient due to a differing chloride concentration that triggers the color change.

Microbiologically influenced corrosion (MIC) caused by sulfate-reducing bacteria (SRB) is a major threat to buried pipelines. The crevices beneath disbonded coatings provide the environment for the survival and growth of SRB, accelerating the attachment of SRB and significantly reducing the effectiveness of buried pipelines. In this work, the influence of initial pH values (6.4, 8.0) and SRB concentrations (2.0 × 10¹, 4.5 × 10², 2.5 × 10³ cells/mL) were investigated on the behaviors of L415 carbon steel. The results indicated that the overall uniform corrosion rate of L415 carbon steel decreased while the maximum pitting corrosion rate exhibited an increasing trend with the increasing of initial concentration of SRB. In comparison to the pH 6.4 environment, the overall risk of pitting corrosion in pH 8.0 environment was reduced due to the biomineralization of SRB, enhancing the protection of metal materials.

The study investigates the practical application of cyclic wet/dry corrosion tests in simulated industrial atmospheres to assess the impact of chromium (Cr) on the protective properties of vanadium micro-alloyed weathering steels. Two types of steels were examined: a V-N steel and a V-N-Cr micro-alloyed weathering steel. These steels were subjected to corrosion tests with 0.01 mol/L NaHSO₃ at a pH range of 4.4–4.8 for varying durations. The findings indicate that the inclusion of Cr in the composition of vanadium micro-alloyed weathering steel enhances corrosion resistance and leads to the accumulation of Cr in the inner rust layer. Furthermore, the distribution of corrosion-resistant elements (Cr, Ni, Cu, P, and Mo) in V-N and V-N-Cr steels is analyzed. The rust layer was observed to exhibit stratification in the corrosive environment, with the outer layers being dense and uniform, while the inner layers were porous and exhibited poor adhesion to the matrix. The study also delves into the anticorrosion mechanism of vanadium weathering steel using techniques such as X-ray diffractometer, electron probe microanalysis, and potential-phase diagram.

Two expired Tetracycline-based antibiotics (Oxytetracycline and Tetracycline) were utilized as eco-friendly corrosion inhibitors for mild steel in 1M HCl solution, employing weight loss analysis, electrochemical measurements, scanning electron microscopy, and so on. The effect and mechanism were discussed using thermodynamic modeling, quantum chemical calculation, molecular dynamics simulation, and so on. The corrosion inhibition rate (η) increases with higher concentration and temperature, leading to reduced heat absorption and increased order degree. The $��\; ��{\eta }_{\mathrm{pmax}}��$ of Oxytetracycline and Tetracycline was 96.14% and 97.92% at 323.15 K of 2 × 10⁻⁴ mol L⁻¹, respectively. The key factors affecting η in the kinetic model parameters vary at lower concentrations. Both of them belong to cathodic corrosion inhibitors and undergo Langmuir spontaneous adsorption processes involving both physisorption and chemisorption. The disparity in energy levels between the highest occupied molecular orbital and lowest unoccupied molecular orbital, global hardness, electronegativity, molecular polarizability, dipole moment, and transfer electron number are key factors that enhance a corrosion inhibitor's ability to adsorb chloride ions.

The use of simulated solutions is a common practice in corrosion studies to assess easily and quickly the corrosion behaviour of materials in real situations. In this context, it is frequent to substitute tests performed in concrete or mortar with tests performed in porous-like solutions. Particularly, to simulate carbonated concrete, different carbonated porous-like solutions (CPS) are found in the literature. However, it is not known whether the use of these solutions accurately predicts the behaviour of steel bars embedded in carbonated concrete. In the present work, a comparison between the corrosion behaviour of carbon steel in carbonated mortar and in different CPS was performed. It was found that none of the CPS studied in the present work adequately simulate the corrosion behaviour of the steel in carbonated mortar, but the CPS containing high concentrations of carbonates/bicarbonates is the only one that provides corrosion rates close to those obtained in carbonated concrete.

Carbon steel is widely used, but it is prone to corrosion, which can lead to safety accidents. In this study, a novel Ni-SiC coating was synthesized on the surface of carbon steel using a one-step electrodeposition method, and the influence of electrodeposition parameters on the wettability of the coating was investigated. This coating possesses abundant micro-nanostructures on its surface, which, after being placed in a vacuum drying environment for 2 weeks, endows it with superhydrophobic characteristics. Due to its superhydrophobic properties and the rich micro-nanostructures, the corrosion current density of this coating is 1/18.95 that of bare steel. After immersion in a corrosive medium for some time, the polarization resistance value of the coated sample was observed to be 13.05 times greater than that of bare steel, demonstrating its remarkable ability to enhance the corrosion resistance of the surface. The results of this study can provide a reference for the anticorrosion work on carbon steel.

Stress corrosion cracking (SCC) susceptibility of a new nickel-based alloy C-HRA-2 under two types of superheated steam (SHS) (0.1 and 8 MPa) and supercritical water (SCW) (25 MPa) at 650°C was studied through slow strain rate tensile tests at a strain rate of 5 × 10⁻⁷s⁻¹. The results indicate that C-HRA-2 exhibits SCC susceptibility in both SHS and SCW, and the susceptibility increases with increasing pressure. Transgranular fracture (located inside) characterized by dimples/micropores and intergranular fracture (located at the edge) characterized by rock-sugar-like morphology was observed in all specimens. The brittleness of the alloy increases with the increase of medium pressure. A large number of cracks perpendicular to the loading axis were noticed on the gauge surface. The SCC mechanism of C-HRA-2 under steam and SCW is dynamic embrittlement.