Materials and Corrosion-werkstoffe Und Korrosion最新文献

The corrosion and material evaluation study in (a) water-based simulated black liquor and (b) water-based simulated black liquor at super-critical conditions was successful. The conclusion from the testing program was that the most resistant alloy for the defined conditions is the chromium-rich carbon steel candidate P91 (UNS K91560). This is a type of creep strength-enhanced ferritic alloy, which is steel designed to retain strength at high temperatures. The P91 abbreviation represents the material's chemical composition, that is, 9 wt% chromium (Cr) and 1 wt% molybdenum (Mo). Further work is required to conclude the corrosion resistance for the P91 quality at supercritical conditions in the welded condition and to better understand caustic corrosion mechanisms.

High-temperature KCl-induced corrosion in laboratory air was observed in situ utilizing X-ray diffraction. High Cr-containing model alloys (Fe-13Cr, Fe-18Cr-12Ni, and Fe-25Cr-20Ni) were coated with KCl and exposed to dry air at 560°C. KCl-free alloys were studied in the equivalent atmosphere as a reference. After exposure to KCl-free environments, all alloys showed the formation of very thin oxide layers, indicating good corrosion resistance. In contrast, KCl-bearing alloys showed distinct damage after exposure.

The increasing use of weathering steels (WS) has raised concerns regarding the diffuse emission of alloying elements. This research paper investigates the release of iron (Fe) and the alloying elements (Cr), copper (Cu), manganese (Mn) and nickel (Ni) from two commercially available WS at urban field conditions in Stockholm, Sweden, during 1 year and in the laboratory at simulated urban conditions. The amount of released metals is evaluated and compared with recommended levels of metals in drinking water and the formation and evolution of the protective patina is studied in parallel to assess the influence on the metal release process. Only minor amounts of the alloying elements are released and is only linked to the outermost surface composition of the patina during the very beginning of the exposure. The released amounts are found to be lower compared with the corresponding levels recommended by the World Health Organisation for drinking water.

The crevice corrosion behavior and mechanism of AA7075-T651 aluminum alloy was investigated by electrochemical measurements and surface analysis technologies in a neutral nitrate solution with different contents of NaCl. The Cl⁻ was identified as crucial for the initiation and development of the crevice corrosion, with the phenomenon absent in the 0.05 M NaCl solution but initiated in the 0.5 and 1 M NaCl solutions. However, the crevice corrosion was more pronounced in the 0.5 M NaCl solution due to the establishment of a larger galvanic corrosion effect. The rapid dissolution of the anodic phase resulted in the increased Cl⁻ inside the crevice, while the cathodic phase enhanced the localized dissolution through micro-galvanic corrosion. This synergistic effect significantly facilitated the development of crevice corrosion.

In this work, cerium conversion coating (CeCC) was deposited on AZ91D Mg alloy using potentiostatic polarization method combined with phosphate pore-sealing treatment. Initially, the optimum deposition parameters to obtain a crack-free surface were found. The characterization of coating revealed the presence of a nodular morphology of cerium oxide deposits. Next, the electrochemical behavior of the coated surface was assessed using potentiodynamic polarization and electrochemical impedance spectroscopy in 3.5 wt% NaCl solution. Based on electrochemical characterization, the coating exhibited a fivefold increase in the charge transfer resistance and a corresponding 76% reduction in corrosion rate, when compared to the bare surface. Furthermore, the conversion coating exhibited improved corrosion resistance when evaluated using the immersion test. Therefore, these findings demonstrate the feasibility of the potentiostatic method for creating nearly crack-free CeCC on Mg alloys, unlike conventional conversion coatings. Moreover, this approach holds great potential for effectively mitigating the corrosion issues in Mg alloys.

Low oxygen environments in biomass gasification and the presence of chlorine in feedstocks can influence the corrosion rate of steel by affecting the formation of protective oxide scales. The effect of KCl on the high-temperature corrosion of low-alloyed steel (13CrMo4-5) under low oxygen partial pressure is investigated by KCl salt spray (0.1 mg·cm⁻²) and exposure to 3 vol% H₂ + 30 vol% H₂O + Ar (balance) at 500°C for up to 168 h. Specimens without KCl salt are exposed for reference. Specimens are characterized after exposure by mass change, SEM/EDS, and XRD. KCl-deposited specimens exhibit about 30% lower mass gain after exposure compared to non-sprayed specimens. Their scale shows a porous innermost layer and a denser layer on top. No Fe or Cr chlorides are identified. The specimens without salt exhibit a similar two-layered scale, with a porous inner Fe-Cr oxide, followed by a denser and thicker Fe-oxide above. KCl could potentially protect the surface from further degradation by physically covering the specimen, altering the scale morphology, and forming a less permeable barrier, hindering the transport of species through the scale.

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Above: Photos of the alloy 601 sample, heat 165306, grain size 267 μm, after exposure of 754 h. Below: Photos of the alloy 602 CA samples, heat 155202, grain size 85 μm after exposure of 2683 hours. ^[a]Sample thickness.

More detailed information can be found in: Heike Hattendorf, Chrétien G. M. Hermse, Richard M. IJzerman, Influence of sample thickness and microstructure on metal dusting behavior of NiCrFeAl alloys, Materials and Corrosion 2024, 75, 560.

Aluminum alloys are widely used in automotive construction, and since the introduction of biogenic ethanol into fuels, the issue of nonaqueous alcoholate corrosion has become an important topic. In this paper, the kinetics of AA1050 temperature-induced alcoholate pitting corrosion are examined experimentally with a specially constructed microreactor. The generated data are utilized to create a phase field model for the pit growth phase. The effects of ethanol-blend composition and water content are quantitatively assessed and simulated. Phase field simulations allow for the first time the mechanistic characterization of the chemical corrosion process with a water content of up to 0.3% and an estimation of relevant reaction parameters at temperatures of up to 150°C. The approach can further be utilized to develop strategies for minimizing corrosion risk in-service.