Band 42, Heft 6

Metal mine tailings (MMT) are a kind of industrial solid waste, with an increasing accumulation year by year, which has seriously damaged the ecological environment. Incorporating MMT in ultra-high performance concrete (UHPC) is an effective means to achieve green sustainable development, which can not only make wastes be resources and prevent pollution but also save raw material costs and reduce energy consumption. However, metal mine tailings contain complex and diverse metal oxides and other chemical substance and even contain certain radioactive elements and heavy metal ions. These factors can affect the corrosion resistance of UHPC, accelerate its aging and damage, and in addition may have serious impacts on the environment and human health. This paper summarizes the material properties of MMT and its application in UHPC; analyzes the effects of MMT as powder or fine aggregate on the workability, mechanical properties, durability, and leaching toxicity of UHPC; and elaborates the hydration products, interfacial transition zone, and pore structure of UHPC incorporating MMT (MMT-UHPC). Based on previous research results, the relationship between flowability, flexural strength, porosity, and compressive strength of MMT-UHPC is established.

As exploration and development to the ultra-deep layer continue to advance, bottom hole temperatures have gradually increased, aggravating acid corrosion of the downhole pipe string and greatly challenging the safety of reservoir reconstruction. Hydrochloric acid (HCl), an inorganic acid with strong acidity, is widely used in common acid systems in oil fields. Therefore, the prevention of corrosion by HCl under high temperature is an important task. In this study, we analyze the molecular structure, synergistic effect, and inhibition mechanism of imidazoline, Mannich base, quaternary ammonium salt, and other high-temperature HCl inhibitors and green inhibitors to explore the temperature resistance of inhibitors from the perspective of molecular microstructure and provide guidance for the development of ultra-high-temperature acidification inhibitors. Finally, the advantages and disadvantages of various HCl corrosion inhibitors are compared and summarized, and the knowledge gap and future research direction in the development field of high-temperature HCl corrosion inhibitors are pointed out.

Plant extracts represent abundant sources of biomolecules distributed throughout various plant parts. These biomolecules are extracted using diverse solvents and methods. Within these plant extracts lie bioactive compounds, known for their antioxidant properties and anticorrosive capabilities. Detecting and isolating these active biomolecules from plant extracts necessitates analytical techniques such as gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry. The active biomolecules within plant extracts contain heteroatoms within their structures, facilitating their adsorption on steel surfaces and conferring corrosion inhibition properties. The advantages of plant extracts as green corrosion inhibitors include ready availability, ease of application, eco-friendly characteristics, and cost-effectiveness. These extracts adhere to steel surfaces, blocking their active sites and effectively reducing the corrosion rate. This review consolidates the findings on the corrosion inhibition potential of plant extracts from various plant parts, elucidating their performance in different concentrations of sulfuric acid.

Reinforced concretes are the primary materials in coastal and offshore engineering. In alkaline environment of concrete, the anodic process is passivation of rebars and the conjugated cathodic process is oxygen reduction reaction (ORR). It is proposed that a novel approach to enhance the passivation films through catalyzed ORR by iron meso-tetra(4-carboxyphenyl)porphine (FeTCPP). The ORR catalyst FeTCPP promotes the formation of passivation film, as it accelerates the consumption of abundant electrons generated and accumulated by the anodic formation of passivation films. The passivation films of rebars are highly defective Fe 3 O 4 semiconductor. The dissolution of interstitial ferrous ions and lattice iron ions produces defects of O ion vacancies, Fe ion vacancies and interstitial Fe ions, and they further cause the formation and accumulation of Fe atom vacancies on the metal surface, leading to the collapse of the passivation films. The FeTCPP adsorbs on the surface of passivation films, hindering the dissolution of lattice iron ions and interstitial ferrous ions, thereby inhibiting the generation and accumulation of Fe atom vacancies and improving the integrity and protective ability of the passivation films.

Corrosion exposure study was conducted on the commercial nickel-based K411 superalloy in a simulated gas turbine operating environment (air + 2 vol% SO 2 ) at 900 °C up to 2000 h. The corrosion behavior of the alloy was quantificationally analyzed from both morphological and chemical points with SEM, XRD, EDS, and EPMA. The results show that the formation of fine TiN inside the oxide layer can be strongly accelerated with the introduction of SO 2 . Sulfide is assumed as diffusion channels for gas molecules that accelerate internal nitridation. Large-volume variation caused by the TiN formation leads to a stress gradient, which induces Cr and Ni elements from inside to the surface of the alloy. The oxide scales release the compressive stresses generated by internal nitridation through forming protrusions on the surface, which is a potential risk for alloy failure. The corrosion behavior of K411 superalloy is controlled by a combination of oxidation, sulfidation, and internal nitridation whereby the relevant corrosion mechanism has been given.

This work presents a multiscale theoretical investigation into the potential of quinoxaline derivatives (Q1–Q6) as corrosion inhibitors for various metals (Fe(110), Cu(111), and Al(110)). Employing a combined approach combining density functional theory (DFT) and Monte Carlo simulations, we explore the relationship between molecular structure, electronic properties, and adsorption behavior. Density functional theory (DFT) and molecular dynamics simulations (MDS) were used to investigate the electronic characteristics of diverse compounds. The study included key parameters including highest occupied molecular orbital energy ( E HOMO ), lowest unoccupied molecular orbital energy ( E LUMO ), energy gap ( E g ) between E LUMO and E HOMO , dipole moment, global hardness, softness ( σ ), ionization energy ( I ), electron affinity ( A ), electronegativity ( χ ), back-donation energy E b−d , global electrophilicity ( ω ), electron transfer, global nucleophilicity ( ε ), and total energy (sum of electronic and zero-point energies). These properties, alongside adsorption energies (following the trend Q6 > Q2 > Q3 > Q4 > Q5 > Q1), are used to identify promising inhibitor candidates and establish structure–property relationships governing their effectiveness. The results suggest that inhibitor efficiency increases with a decreasing energy gap between frontier orbitals. Notably, the protonated state of Q6 exhibits high reactivity, low stability, and strong adsorption, making it a potential candidate for further exploration. This comprehensive theoretical approach offers crucial insights for the conceptual development of new and powerful corrosion inhibitors.