Materials and Corrosion-werkstoffe Und Korrosion最新文献

The paper focuses on the excellent chemical inertness characteristics of nonmetallic materials and evaluates the performance of three types of new carbon fiber-reinforced resin-based composites under various simulated corrosion conditions in wellbores. Through comprehensive analysis of macro and micromorphology, moisture absorption performance, strength performance, and molecular structure, the damage characteristics and applicability of carbon fiber composites in oil and gas wellbore conditions were clarified. T700/epoxy and T300/epoxy composites experienced damage dominated by physical effects such as moisture absorption and wet thermal stress, manifested as swelling, deformation, and cracking at the macro level, and pore formation and delamination cracking at the micro level. After continuous corrosion tests, the tensile strength of T700/bismaleimide composite (913 MPa) was higher than that of T700/epoxy composite (814 MPa) and T300/epoxy composite (636 MPa), with reductions of 12.4%, 14.3%, and 19.5% respectively. The research results showed T700 carbon fiber/bismaleimide resin composites had the best mechanical and chemical stability.

Weathering steel (WS) and high-performance steel (HPS) have been widely used in bridge engineering. Investigating the corrosion performances of WS and HPS is of great significance to the safety evaluation and maintenance of uncoated WS or HPS bridges, especially aging bridges. This study focused on the correlation between the corrosion performance and composition of the rust layer. Accelerated corrosion tests were conducted on Q345CNH and HPS 70 W to observe their corrosion performance under salt-spray corrosive environment. Based on the results of corrosion test and the existing corrosion attack evaluation theories, the empirical formulae of uniform corrosion and pitting corrosion were derived. X-ray diffraction experiments were performed to analyze the composition of the rust layer formed on the surface of steel specimens after various corrosion cycles. The relationship between the composition of the rust layer and the corrosion performance was established. The test corrosive environment was verified to be consistent with the C3 environment. The conclusions of this study could provide guidance for the corrosion evaluation in the following test or practical application.

The dissolution mechanism of phases c-Ti_0.5Al_0.5N, c-aluminium nitride (AlN), c-TiN, and Al₂Ti, and elements of the Ti_1–xAl_xN coatings (for x < 0.6) in 3 wt.% NaCl solution is described based on the results of X-ray diffraction analysis, energy-dispersive X-ray spectroscopy, and scanning electron microscope and previous electrochemical tests. Researchers studied the protective effectiveness of Ti_1–xAl_xN coatings in 3 wt.% NaCl solution by analyzing the factors: composition, thickness, porosity, total energy of ground state, stresses, structure, and texture. It was first established that the additional c-TiN phase with R_pmax and E_cormax, and secondary phase Ti_0.70–0.82N formed after Al's dissolution in the main phase c-Ti_0.5Al_0.5N increases the N content and prevents the Ti dissolution in the Ti_1–xAl_xN coatings. The phase c-AlN with i_cormin reduces the dissolution rate of Al in the c-Ti_0.5Al_0.5N phase. The stoichiometric c-Ti_0.5Al_0.5N is the most thermodynamically stable phase. The described phase transformations in Ti_1–xAl_xN coatings during phases dissolution in 3 wt.% NaCl can predict the coating protective effect. A multilayer coating with layers of c-AlN, c-TiN, and c-Ti_0.5Al_0.5N is recommended for industrial use.

Carbonation-induced corrosion of steel in concrete can allow for premature degradation of structures. Corrosion probes in health monitoring systems can assess concrete carbonation and steel corrosion rates. The electrochemical noise (EN) technique has advantages for corrosion sensing. Instrumented concrete columns were fitted with a carbonation chamber for accelerated testing. EN was assessed through statistical evaluation of noise time signatures, noise resistance, and spectral analysis. The mean noise potential for the electrodes showed electronegative potential and correspondingly high rms noise current, indicative of corrosion activation in carbonated concrete. The estimated corrosion rates obtained from the noise impedance were comparable to those resolved from the polarization resistance and noise resistance. The shot noise analysis indicated isolated spontaneous noise events associated with the activation of local steel anodes. The outcomes of the testing indicate that the placement of low-cost sensors and passive EN measurements can be used to monitor the onset of carbonation-induced corrosion of steel in concrete and provide estimates on corrosion rates.

In this paper, the passive behavior of 304 stainless steel (SS) in NaCl solution is studied by electrochemical methods and surface analysis. The polarization measurement results show that the pitting potential (E_p) has a simple linear relationship with the temperature increase. Scanning Kelvin probe results show that the surface potential difference on the surface of 304 SS is well correlated with the temperature. Scanning electron microscope results show that the rupture of the passive film accelerates with the increase of temperature. The X-ray photoelectron spectroscopy analysis shows that the high temperature causes more oxidation on the surface of 304 SS, leading more Cr³⁺ oxidized to Cr⁶⁺ at high temperature.

A two-step corrosion experiment was performed on a ferritic steel (Armco) in a synthetic solution representing the Callovo–Oxfordian at 120°C. After the development of a carbonated corrosion product layer (CPL) during the first 15 days of the experimental step, corrosion front progression was investigated using ¹³C marked carbonate species during the second 15 days experimental step. CPL was characterized at each step, in terms of morphology (scanning electron microscopy), composition (energy-dispersive spectroscopy), and structure (µ-Raman). ¹³C corrosion product locations were analyzed by time-of-flight secondary ion mass spectrometry. Results evidenced that after a step of generalized corrosion, iron corrosion continues locally at the metal/CPL interface. These results suggest that although a protective siderite layer formed on the iron surface after 15 days, a local dissolution of the carbonate layer at the M/CPL interface occurred. A galvanic effect is developed between the bared surface (anode) and the covered one (cathode). This activates iron oxidation. The precipitation of carbonate corrosion products to the metal/CPL interface is possible by the diffusion of ¹³CO₃²⁻ ions from the bulk through the siderite layer.

Lightweight high entropy alloy (LWHEA) has great potential in aeroengine hot component applications. Anticorrosion property of LWHEA at high temperatures is one of the key determining factors. In this study, an LWHEA containing Al, Nb, Ti, V, and Zr elements with a molar ratio of 2: 1: 3: 2: 1 was designed and prepared by low energy (LE) and high energy (HE) mechanical milling followed by vacuum hot pressing. The sintered LE alloy consisted of a simple cubic matrix and α intermetallic while the BCC matrix along with α and β intermetallic phases were observed in HE alloy. The oxidation of LE and HE at 1000°C for 48 h was mainly concentrated on α and β phases, and the resultant oxides were ZrO₂ and TiO₂. Weight gain curve of HE sample within oxidation time of 48 h followed the parabolic law while a two-stage parabola was found in LE bulk. The steady-state oxidation of α precipitate was dominant within 12 h and showed a preferential oxidation mode. High temperature induced simple cubic matrix to stable BCC phase transformation and thus LE alloy with longer oxidation time and HE exhibited a similar uniform oxidation. The oxidation rate of the alloy is related to the content of α and β phases.

The present study investigated the dissolution and oxidation corrosion behaviors of Hastelloy exposed to static liquid lead-bismuth eutectic (LBE) at 500°C with an oxygen concentration of 1 × 10⁻⁶ mass%. Hastelloy exhibited better LBE corrosion resistance than the Monel alloy. Both dissolution and oxidation corrosion were observed in Hastelloy, and the maximum LBE penetration depth and spinel layer thickness in the corroded sample after 4000 h of exposure reached 120 ± 36 and 21 ± 12 µm, respectively. Annealing twin boundaries provided favorable paths of accelerated LBE penetration into the matrix, resulting in selective leaching of Ni. Microstructural characterization revealed that the spinel layer formed between penetrated LBE and base metal slowed down the elemental interdiffusion, thereby retarding the dissolution rate. Volumetric changes induced by LBE penetration promoted the formation of stacking faults and dislocations, which could provide more channels for elemental diffusion, leading to the propagation of dissolution attack.

The paper presents the results of non-destructive testing examinations, metallographic tests and risk assessment of degradation related to corrosion of amine regeneration unit in a desulphurisation system. Intensive corrosion resulting from acid gases environment upon water condensation causes perforation of the pipeline. Detailed analysis reveals cracking related to the mechanism of wet H₂S. Hydrogen penetration, resulting from the wet H₂S process, causes a decrease in mechanical properties of steel and an increase in hydrogen content inside steel. Corrosion results mostly from high stream velocity, the presence of acid gases (with high ammonia content), the presence of amine and low stream temperature.