Materials and Corrosion-werkstoffe Und Korrosion最新文献

The study investigated the effect of the oxidation–reduction cycles on the structure and corrosion resistance of the Haynes 282 nickel superalloy at ambient and elevated temperatures. The comparative studies were performed on specimens produced by the Powder Bed Fusion-Laser Beam (PBF-LB) process and those in the as-received state. The microstructure of the PBF-LB specimens was studied using optical and scanning electron microscopy, whereas the chemical composition of the scale formed after isothermal oxidation in an air atmosphere at 750°C was analysed using energy-dispersive X-ray spectroscopy and X-ray Photoelectron Spectroscopy. The phase composition of the formed scale was determined by X-ray diffraction. Laboratory-induced hydrogen atmosphere was adopted through cathodic charging. A comparison of corrosion resistance was carried out on two types of Haynes 282 specimens, before and after the oxidation and cathodic charging processes. It was found that PBF-LB process could be effectively used to manufacture Haynes 282 nickel superalloy with low porosity and a fine crystalline microstructure. The low-porous, fine-crystalline microstructure of the tested specimens produced by the PBF-LB technique exhibited good resistance to electrochemical corrosion, slightly lower than wrought Haynes 282 nickel superalloy specimens.

Flow-accelerated corrosion (FAC) is a complex phenomenon that poses a significant threat to the integrity of piping and fittings in power plants, affecting infrastructure protection and power production reliability. The presence of corrosive substances in the fluid and elevated flow velocity and temperature leads to increased material loss in piping and equipment. Understanding the intricate relationship among the contributing factors such as flow dynamics, environmental factors, and corrosion reactions is essential for developing effective prediction and mitigation strategies. This review discusses the recent advancements in the numerical modeling of FAC using computational fluid dynamics (CFD). The numerical models presented show abilities to predict FAC profiles across multiple power plant components, and a review was conducted on the evaluation of these predictions with experimental measurements. Notably, increased turbulence in the flow significantly contributed to prediction errors, emphasizing the need for advanced turbulence models in numerical simulations of FAC. Addressing these challenges is crucial for maintaining sustainable infrastructure and reducing industrial risks through enhanced predictive maintenance strategies.

Zn–Al–Mg coatings contain Zn phase and Zn/Mg–Zn, Zn/Al, and Zn/Al/Mg–Zn eutectics. The formation and evolution of corrosion products on different eutectics that affect the corrosion resistance of Zn–Al–Mg coatings require further exploration. In this work, the formation and evolution of corrosion products on different microstructures were investigated. The results show that while the corrosion products on different microstructures are mainly Zn₅(OH)₈Cl₂, the phase composition and morphology of corrosion products vary significantly. These differences in corrosion products on each microstructure were discussed in detail. The corrosion protective properties of corrosion products on different microstructures were compared. The protective properties of corrosion products are closely related to the content and morphology of Zn₅(OH)₈Cl₂ and Zn₆Al₂(OH)₁₆CO₃. The corrosion products on Zn/Al/Mg₂Zn₁₁ eutectic are the finest and densest, with high content of Zn₅(OH)₈Cl₂ and Zn₆Al₂(OH)₁₆CO₃, showing good protective performance. Increasing the content of Zn/Al/Mg–Zn eutectic to enhance the corrosion resistance of Zn–Al–Mg coatings should be considered in the subsequent work.

To evaluate the global seawater corrosivity and ensure the service safety of marine equipment, the methods of seawater corrosivity classification, which contained the standard metal corrosion rates method and the environmental factors evaluation method, are proposed and then applied to the seawater corrosivity classification in typical China seas. By comparing the results from both methods, the feasibility of the environmental factors evaluation method based on the grey relational model is verified. Furthermore, with the collection and processing of typical seawater factors data of global ocean, the corrosivity of global seawater is classified into six grades with the corrosion test data of carbon steel as baseline, and its distribution in different months is visualized by means of ArcGIS technology. The results show that the sea areas with high corrosivity are mainly located at equatorial and tropical sea areas, and for carbon steel, seawater temperature was the main influence on seawater corrosivity.

Dissimilar metal welds are utilized in the energy industry to connect two materials with different material characteristics. In the case of nuclear power plants, the connected materials tend to be low-alloyed steel and high-alloyed material. Despite different material and corrosion properties, under the proper environmental conditions, the used construction materials and weld metals are protected either by a passive layer or by a high-temperature oxide. Although dissimilar metal welds are used in both primary and secondary circuits, the most frequently documented damage is in the secondary circuit, where, in addition to material heterogeneities, local environmental heterogeneities may form. For dissimilar metal welds in WWER nuclear power plants, a water–water energetic reactor, a subtype of pressure water reactor, we note two main types of attack near the dissimilar fusion boundary: on the carbon steel side or on the high-alloyed weld metal side (X10CrNiMoN16-25-6). The possible causes of the latter “atypical” corrosion attack are debated and can be generalized as a consequence of change of the grain boundary condition.

The corrosion of 2198 aluminum–lithium alloy in a marine atmospheric environment was simulated using a wet–dry alternating experimental setup. Weight-loss measurement methods, electrochemical impedance spectroscopy (EIS), scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS), macroscopic morphology testing, three-dimensional morphology testing, and X-ray photoelectron spectroscopy (XPS) were used to study the wet–dry alternating corrosion behaviors and mechanisms of 2198 aluminum–lithium alloys under simulated marine atmospheric environment. The results indicate that corrosion weight loss increases with decreasing wet-to-dry ratios, accompanied by an increase in the corrosion rate. Various data suggest that the primary corrosion products are composed of Al₂O₃, AlO(OH), and AlCl₃. The reduction in the wet-to-dry ratio leads to the enrichment of Cl⁻ within the corrosion products, extending the contact time between the substrate and the medium, thereby intensifying the hydrolysis of Al³⁺. This exacerbates the dissolution at pitting sites, which in turn erodes and breaks down the corrosion product film, accelerating the overall corrosion process.