Materials and Corrosion-werkstoffe Und Korrosion最新文献

The Martinique island, located in the Caribbean Sea, is subject to the stranding of Sargassum algae, which decompose and release toxic gases, such as hydrogen sulfide or ammonia. This study aims to investigate the atmospheric corrosion of zinc in these conditions. For this purpose, three sites in Martinique more or less impacted by Sargassum algae stranding were selected. Mass loss results after 1-year exposure range from 1.9 µm for the site least impacted to 45.3 µm for the site most affected by Sargassum algae. This high value proves that the presence of Sargassum algae caused significant zinc degradation. The morphological structures and properties of the corrosion products obtained at the impacted and non-impacted sites differ significantly. In the absence of Sargassum algae, “classical” corrosion products based on hydrozincite, simonkoleite, gordaite, and zinc hydroxylsulfate are observed. In the area close to the Sargassum seaweed stranding, the presence of elemental sulfur products, zinc hydroxylsulfate, and sphalerite is reported.

In this research work, a real case of failed ASTM A860 WPHY 65 long elbow pipe coated with inorganic zinc ethyl silicate primer is collected from a treatment facility to investigate the root causes of its failure, which was reported after approximately 28 months of use. The failure was investigated using visual observations, metallurgical analysis using optical emission spectroscopy, mechanical testing, X-ray diffraction of corrosion product, chemical analysis of sewage and corrosion rate test of the elbow using a three-electrode potential technique, fractographic analysis using scanning electron microscope along with computational analysis to confirm the results. Through the testing, it was observed that severe depletion in the strength can be attributed to erosion–corrosion caused by various impurities present in the sewage, leading to the generation of corrosion pits and turbulent eddies and stresses generated due to sudden changes in fluid flow direction along with gases present in sewage reacting with a base metal. Various failure mechanisms that have led to pipe failure are discussed in this paper, along with a listing of preventive measures to delay it.

The effects of biodegradable corn peptone on the corrosion behavior of mild steel in 0.1M HCl were evaluated. The results from the weight loss experiments indicate that changing the amount of corn peptone from 50 to 500 ppm considerably decreased the corrosion rate of the coupons from 28.24 to 4.67 mpy. However, heating the solutions had negative effects on this trend. According to the calculations, dissolving the inhibitor modified the thermodynamic parameters of the corrosion phenomenon. In addition, the adsorption of corn peptone was best fitted with the Langmuir isotherm. The Tafel polarization plots revealed that the presence of corn peptone decreased the corrosion current density from 134.9 to 6.7 µA cm⁻². This was compatible with the electrochemical impedance spectroscopy data. Furthermore, X-ray photoelectron spectroscopy analysis confirmed the adsorption of the tested peptone on the surface of the working electrodes, which based on the atomic force microscope images, reduced the surface roughness of the specimens.

The corrosion behavior of unaged and thermally aged Ni–25Cr–10Fe–3Si–xMo (x = 0, 3 wt%) alloys was studied beneath KCl–ZnCl₂ deposits at 650°C. The results indicated that the addition of Mo promoted the formation of a continuous Si-rich protective layer and improved the corrosion performance of the unaged Ni–25Cr–10Fe–3Si–xMo alloys. The precipitates formed after long-term aging greatly affect the corrosion resistance of the thermally aged alloys. The M₂₃C₆ along the grain boundaries is beneficial to improve corrosion resistance, however, the dispersed Laves phase and Sigma deteriorate corrosion resistance.

The hot corrosion resistance of 8 wt.% yttria-stabilized zirconia (8YSZ) powder, modified with CaO, MgO, Ta₂O₅, and TiO₂ at concentrations of 5, 10, and 15 wt.%, was systematically investigated in a molten vanadium pentoxide (V₂O₅) environment at 900°C and 1100°C for 48 h. The modified 8YSZ samples, coated with V₂O₅, underwent thermal cycling totaling 12 cycles. Results revealed susceptibility to hot corrosion for all doped 8YSZ powders, attributed to tetragonal ZrO₂ destabilization, forming monoclinic ZrO₂. Remarkably, 8YSZ/CaO demonstrated exceptional resistance to hot corrosion when exposed to a temperature of 900°C. The corrosion product found in the 8YSZ/Ta₂O₅ material was determined to be tetragonal Zr_0.66Y0.17Ta_0.17O₂. Although, 8YSZ/TiO₂ undergoes deterioration at 900°C, it exhibits improved resistance at 1100°C, resulting in the formation of TiVO_4.

Three FeCrAl alloys (APMT, EF100 and EF101) from Kanthal® and the reference Ni-Cr Alloy 625 were used as weld cladding materials on tube shields in the evaporator tube bank of a waste-fired combined heat and power plant. For each alloy type, the overlay welded tube shields were placed in both roof and floor positions within the evaporator for 6 months. The metal-loss rate, the microstructure and hardness of the overlay welds before and after exposure and the corrosion products were analysed. The results showed higher metal-loss rates in the welds placed in the roof position, confirming heterogeneities in the evaporator bank environment. Alloys were ranked from higher to lower erosion–corrosion resistance as follows: APMT ≈ Alloy 625 > EF101 > EF100. The analysis of the corrosion attacks showed a significant variation among the alloys, from a primarily homogeneous corrosion attack on APMT to intergranular corrosion in EF100 and pit formation in EF101.

This work aims to analyze the passivation and pitting corrosion behaviors of laser beam welded R60702 zirconium alloy in neutral and acidic chloride-containing electrolytes. Potentiodynamic polarization and electrochemical impedance spectroscopy measurements are carried out to investigate the electrochemical performance of the welding joint. Scanning electron microscope, X-ray diffraction, and three-dimensional profile digital microscope are utilized to reveal the microstructures and corrosion morphologies. The electrochemical results show that the heat-affected zone (HAZ) and weld zone have nearly equal corrosion performance, and both of them are more corrosion-resistant than the base metal. The corrosion morphologies suggest that the HAZ has the lowest sensitivity to pitting corrosion. Moreover, it is unraveled that, in chloride-containing electrolytes, the quantity and distribution of Zr(Fe,Cr)₂ particle phases are the main factors that determine the different corrosion performances of the welding joint.

Arumugam Madhan Kumar, Ihsan ulhaq Toor, Materials and Corrosion. 2022;1–14. DOI: 10.1002/maco.202213174

In the acknowledgments, on page#15, row#52, research grant# is mentioned as INAM2014, which is a typographic error and needs to be corrected as “INAM2104”.

In elevated conditions, austenitic stainless steels suffer intense damage by corrosion because of the severe oxide scale development. Giving stainless steel a corrosion-resistant surface coating can prevent excessive damage. In this case, welding-based overlaying is a potential method to restore the damaged parts as it has a higher productivity rate. This investigation articulates the corrosion resistance behavior of the multiple overlapped Inconel 625 (IN625) weld overlays on the AISI 316L substrate plate. The corrosion resistance at elevated temperatures was investigated with kinetic curves, further revealing the corrosion products from the sample surface. Characterization techniques like scanning electron microscopy with energy-dispersive spectroscopy, X-ray diffraction, and Raman spectroscopy were employed to analyze the corrosion products. Hot corrosion kinetics in the molten salt environment (Na₂SO₄ + V₂O₅) revealed that the IN625 overlay samples gained a weight of 40.15 mg/cm², and the substrate had a weight gain of 65.42 mg/cm². From the hot oxidation kinetics, it is evident that the mass gained by the substrate is more than twice that of the Inconel overlay sample. Furthermore, the formation of oxides and spinel phases rich in nickel (NiO, NiCr₂O₄) highly influenced the corrosion kinetics of the multiple overlapped IN625 overlay sample. The AISI 316L substrate sample revealed the existence of critical oxide phases such as Fe₂O₃ and Cr₂O₃, which were lesser and did not influence the corrosion resistance at 900°C. In the present investigation, the multiple overlapped IN625 weld overlay offered excellent corrosion resistance at high temperature compared to the AISI 316L.

The corrosion behavior of 310S austenitic stainless steel, subjected to different surface treatments machined (MA), sandblasting (SB), and polishing (PO), was exposed to a 550°C supercritical water (SCW) environment. The aged samples were analyzed using variable-energy slow positron beam techniques. The obtained results revealed that the plastic deformation of the near-surface region of the MA and SB samples was substantially recovered in the SCW conditions. At least two distinct oxide layers formed, and the oxidation process created a Fe/Cr depletion zone in the inner layer. Various surface treatments, however, led to different corrosion profiles. The depth profile of slow positron beam characterization suggests that significant residual stress and deformation zones on the surfaces of the sandblasted samples probably provided a diffusion path for the oxidation of the 310S. Only the SB samples exhibited a negative weight change after SCW exposure. At the same time, the SB samples showed the highest concentration of the positron traps in this region, which was explained by open-volume defects associated with the microcracks introduced by sandblasting.