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21 pages, 4837 KiB

Open AccessArticle

Research on Modified Thermal Barrier Coatings Against CMAS Corrosion Driven by Mechanism–Data Hybrid Model

by Dongdong Ye, Feixiang Wu, Zhou Xu, Yiwen Wu, Changdong Yin, Huanjie Fang and Houli Liu

Coatings 2024, 14(12), 1513; https://doi.org/10.3390/coatings14121513 - 30 Nov 2024

Viewed by 993

Abstract

With the development of high-efficiency gas turbine engines and increasing inlet temperatures, the performance of thermal barrier coatings (TBCs) for hot-section components has been more severely challenged. The doping of multi-element rare earth elements significantly improves the thermodynamic properties and chemical compatibility of [...] Read more.

With the development of high-efficiency gas turbine engines and increasing inlet temperatures, the performance of thermal barrier coatings (TBCs) for hot-section components has been more severely challenged. The doping of multi-element rare earth elements significantly improves the thermodynamic properties and chemical compatibility of thermal barrier coatings so that the application performance of coatings in high-temperature environments is enhanced considerably. In this work, the doped coatings prepared by REYSZ (RE = La, Sm, Nd) were investigated and characterized in terms of crystal structure, elastic properties, and thermal–mechanical properties based on the first-principles approach, combined with various empirical and semi-empirical formulations, and a predictive model for resistance to CMAS corrosion based on machine learning approaches. The results showed that the tetragonal phase REYSZ material was mechanically stable, had a large strain damage tolerance, and was not easy to fracture under applied loads and thermal shocks. In terms of CMAS corrosion resistance, the NdYSZ interfacial model had a lower surface energy (3.130 J/m²) and Griffith fracture energy (6.934 J/m²) compared with the conventional YSZ model, and Nd₂O₃ had the potential to improve the CMAS corrosion resistance of zirconia-based material for thermal barrier coatings. By evaluating the machine learning prediction models, the regression coefficients of the two algorithms were 0.9627 and 0.9740, and both these two prediction models showed high prediction accuracy and strong robustness. Ultimately, this work presented a novel mechanism–data hybrid method, which would facilitate the efficient development of TBC new materials for anti-CMAS corrosion. Full article

(This article belongs to the Special Issue Corrosion Resistance, Mechanical Properties and Characterization of Metallic Materials and Coatings, 2nd Edition)

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17 pages, 10327 KiB

Open AccessArticle

The Microstructure of Aluminide Coatings on 310S and 347H Steels Formed by Pack Aluminizing and Their Corrosion Behavior in Molten Chloride Salts

by Weiqian Chen, Peiqing La, Zengpeng Li, Yaming Li and Lei Wan

Coatings 2024, 14(12), 1507; https://doi.org/10.3390/coatings14121507 - 29 Nov 2024

Cited by 2 | Viewed by 802

Abstract

In order to enhance the resistance of superalloys to high-temperature molten chloride salt corrosion, Fe-Al coatings were prepared on 310S and 347H stainless-steel surfaces via pack aluminizing. Then, the coatings were annealed at different temperatures to explore the influence of temperature on their [...] Read more.

In order to enhance the resistance of superalloys to high-temperature molten chloride salt corrosion, Fe-Al coatings were prepared on 310S and 347H stainless-steel surfaces via pack aluminizing. Then, the coatings were annealed at different temperatures to explore the influence of temperature on their phase constitution, microstructure, microhardness, and corrosion resistance. The results showed that the annealing temperature had a considerable effect on the corrosion resistance of the Fe-Al coatings, which was related to the change in the phase composition of the coatings that occurred due to the annealing treatment. The growth rate of the coating on 347H steel was higher than that on 310S steel, and their thicknesses from aluminizing at 800 °C for 20 h were 209.6 and 153.5 µm, respectively. When annealing at 900 °C for 30 h, the phase composition of the coatings was completely transformed into (Fe, Cr, Ni) Al. The corrosion loss rate of the annealed coating was clearly reduced, the loss rate of the 310 coating was 6.0 and −0.25 mg/cm² before and after annealing at 900 °C and that of the 347 coating was 4.89 and −0.7 mg/cm² before and after annealing at 750 °C, respectively. The two coatings showed good corrosion resistance to molten chloride salts, as demonstrated by the oxide scale (Al₂O₃) that formed on the surface, which had a thickness of about 30~40 µm. Full article

(This article belongs to the Special Issue Corrosion Resistance, Mechanical Properties and Characterization of Metallic Materials and Coatings, 2nd Edition)

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25 pages, 31111 KiB

Open AccessArticle

Experimental Analysis of Cavitation Erosion: Parameter Sensitivity and Testing Protocols

by SeyedMehdi Mohammadizadeh, José Gilberto Dalfré Filho, Cassiano Sampaio Descovi, Ana Inés Borri Genovez and Thomaz Eduardo Teixeira Buttignol

Coatings 2024, 14(10), 1288; https://doi.org/10.3390/coatings14101288 - 9 Oct 2024

Cited by 6 | Viewed by 1666

Abstract

The scientific goal of this study was to investigate the effects of various parameters on cavitation-induced erosion, with the aim to enhance the understanding and assessment of cavitation resistance in hydraulic systems. Cavitation erosion poses significant challenges to the durability and efficiency of [...] Read more.

The scientific goal of this study was to investigate the effects of various parameters on cavitation-induced erosion, with the aim to enhance the understanding and assessment of cavitation resistance in hydraulic systems. Cavitation erosion poses significant challenges to the durability and efficiency of hydraulic components, such as those found in hydropower plants and pumping stations. Prompted by the need to improve the reliability of cavitation testing and material assessment, this research conducted a comprehensive sensitivity analysis of a cavitation jet apparatus (CJA). This study employed an experimental platform that consisted of a vertical cylindrical test tank, a submerged nozzle, and an aluminum sample. By examining a range of orifice diameters, this research identified that smaller diameters led to increased erosion intensity, with the most pronounced effects observed at a diameter of 2 mm. Furthermore, various standoff distances (SoDs) were tested, which revealed that shorter distances resulted in greater erosion, with the highest impact noted at an SoD of 5 cm. This study also evaluated different nozzle geometries, where it was found that a 132° conical sharped edges nozzle, combined with an orifice diameter of 2 mm and an SoD of 5 cm, produced the most severe erosion. Conversely, chamfered edges nozzles and a commercial nozzle (MEG2510) with an SoD of 10 cm or greater showed reduced erosion. These results highlight that by standardizing the testing duration to 1200 s, the CJA could reliably assess the cavitation resistance of materials. This study established a clear relationship between increased pressure and higher impact forces, which led to more severe erosion. The findings underscore the effectiveness of the CJA in evaluating material resistance under various cavitation conditions, thus addressing a critical need for reliable cavitation testing tools. Full article

(This article belongs to the Special Issue Corrosion Resistance, Mechanical Properties and Characterization of Metallic Materials and Coatings, 2nd Edition)

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19 pages, 8757 KiB

Open AccessArticle

Preparation and Properties of Conductive Aluminum Powder (Al@Si@C) for Water-Borne Heavy-Duty Anticorrosive Coatings

by Qingpeng Li, Jiaxing Liu, Tiancheng Jiang, Xiaoyun An, Na Wang, Zhixiu Xu, Wanyuan Guo, Liang Zhang and Xiaofeng Liu

Coatings 2024, 14(9), 1082; https://doi.org/10.3390/coatings14091082 - 23 Aug 2024

Viewed by 1226

Abstract

To improve the storage stability and conductivity of aluminum powder in an aqueous environment, the surface of aluminum powder was treated to form silica film by the sol–gel method, then was treated with conductive modification to introduce nanocarbon black particles so that conductive [...] Read more.

To improve the storage stability and conductivity of aluminum powder in an aqueous environment, the surface of aluminum powder was treated to form silica film by the sol–gel method, then was treated with conductive modification to introduce nanocarbon black particles so that conductive aluminum powder could be prepared to solve the application bottleneck of aluminum powder in water-borne heavy-duty anticorrosive coatings. The structure, surface morphology, and composition of the modified aluminum powder were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), and X-ray powder diffraction (XRD). The corrosion resistance and electrochemical properties were measured using a hydrogen evolution test and an 2electrochemical test. The results showed that there was a compact SiO₂ film formed on the surface of the prepared conductive aluminum powder, and the conductive filler nanocarbon black was uniformly grafted on the surface. According to the hydrogen evolution test at 100 h/50 °C, conductive aluminum powder with 5 wt% carbon black exhibited the best hydrogen evolution effect, with a hydrogen evolution amount of only 0.5 mL. The prepared conductive aluminum powder was applied to the water-borne coatings, and the storage stability test, electrochemical polarization test, and neutral salt spray test were further conducted. The water-borne coatings prepared with conductive aluminum powder still showed good performance and had no reaction after 6 months of storage. Compared with the coating containing SiO₂-modified aluminum powder, the coating exhibited better corrosion resistance. Full article

(This article belongs to the Special Issue Corrosion Resistance, Mechanical Properties and Characterization of Metallic Materials and Coatings, 2nd Edition)

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13 pages, 5513 KiB

Open AccessArticle

The Influence of Rust Layers on Calcareous Deposits’ Performance and Protection Current Density in the Cathodic Protection Process

by Wei Zhang, Xinran Wang, Haojie Li, Zhifeng Lin and Zhiwei Chen

Coatings 2024, 14(8), 1015; https://doi.org/10.3390/coatings14081015 - 10 Aug 2024

Viewed by 1347

Abstract

Calcareous deposits are a consequential outcome of cathodic protection in marine environments, exerting significant influence on the cathodic protection process and current density prerequisites. This study investigates the process of calcium deposition and its impact on the cathodic protection current density of carbon [...] Read more.

Calcareous deposits are a consequential outcome of cathodic protection in marine environments, exerting significant influence on the cathodic protection process and current density prerequisites. This study investigates the process of calcium deposition and its impact on the cathodic protection current density of carbon steel under the influence of a rust layer in different corrosion periods. This was investigated using electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). The results demonstrate that the formation processes of calcareous deposits vary after exposure to the corrosive environment for 0, 7, and 30 days. While a longer corrosion period leads to thicker rust layers on the metal surface and a higher initial cathodic protection current, the presence of these rust layers facilitates the deposition of calcium and magnesium ions, resulting in a rapid decrease in cathodic protection current density after a certain period. Meanwhile, long-term cathodic protection facilitates the thickening and densification of the oxide layer, thereby enhancing its protective efficacy, effectively reducing the corrosion rate of the metal surface and stabilizing the cathodic protection current density at a lower level. This study provides theoretical data and experimental evidence to support the maintenance of corroded marine engineering equipment. Full article

(This article belongs to the Special Issue Corrosion Resistance, Mechanical Properties and Characterization of Metallic Materials and Coatings, 2nd Edition)

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22 pages, 5062 KiB

Open AccessArticle

Thermodynamic Analysis of Typical Alloy Oxidation and Carburization in High-Temperature CO₂ Atmosphere

by Jing Xiong

Coatings 2024, 14(7), 869; https://doi.org/10.3390/coatings14070869 - 11 Jul 2024

Cited by 2 | Viewed by 1101

Abstract

The corrosion of structural materials is a crucial issue of the application of supercritical carbon dioxide in the Brayton power cycle system. The oxidation and carburization behaviors of typical alloy materials in high-temperature CO₂ environments are studied based on thermodynamic analysis technology, [...] Read more.

The corrosion of structural materials is a crucial issue of the application of supercritical carbon dioxide in the Brayton power cycle system. The oxidation and carburization behaviors of typical alloy materials in high-temperature CO₂ environments are studied based on thermodynamic analysis technology, including the analysis of the oxidation and carburization performance of the CO₂ atmosphere as well as the corrosion behaviors of alloy elements under 500 °C, 600 °C, and 650 °C. In addition, the oxide film characteristics of T91 and 800H alloys, including phase composition and morphology structure, are studied at 500 °C and 650 °C. Research has found that for the T91, FeCr₂O₄ and Fe₃O₄ can form a continuous oxide film layer with coverage and SiO₂, VO, and MnCr₂O₄ oxides are mainly in the inner layer of the oxide film. For the 800H, Cr₂O₃ and MnCr₂O₄ can form flakes of oxide film layers, while Al₂O₃, TiO₂, and SiO₂ are distributed as scattered grains near the interface between the oxide film and the matrix material. Both T91 and 800H will produce chromium carbides, which will reduce the toughness of the material. Full article

(This article belongs to the Special Issue Corrosion Resistance, Mechanical Properties and Characterization of Metallic Materials and Coatings, 2nd Edition)

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17 pages, 12088 KiB

Open AccessArticle

Effect of Temperature and Immersion Time on Corrosion of Pipeline Steel Caused by Sulfate-Reducing Bacteria

by Yulong Wei, Pei Li, Qingwen Liang, Baihong Wu, Junjie Shen, Huifang Jiang and Qingjian Liu

Coatings 2024, 14(7), 807; https://doi.org/10.3390/coatings14070807 - 28 Jun 2024

Cited by 1 | Viewed by 1352

Abstract

Sulfate-reducing bacteria (SRB) are the primary cause of corrosion in oil and gas pipeline steel. To understand how temperature and immersion time affect the SRB-induced corrosion of BG L450OQO-RCB pipe steel, the present study delved into the morphology and elemental composition of corrosion [...] Read more.

Sulfate-reducing bacteria (SRB) are the primary cause of corrosion in oil and gas pipeline steel. To understand how temperature and immersion time affect the SRB-induced corrosion of BG L450OQO-RCB pipe steel, the present study delved into the morphology and elemental composition of corrosion products, corrosion rate, corrosion solution composition, and electrochemical performance at different temperatures (25, 40, and 60 °C) and immersion times (5, 10, and 20 days). During the SRB corrosion of the investigated steel, extracellular polymeric substances (EPSs), iron sulfide, and iron phosphide were produced on the surfaces of the steel samples, along with the calcium carbonate product. Chloride ions in the corrosion solution contributed to the corrosion of steel and the formation of chlorides on steel surfaces. Over time, the quantities of EPSs, iron sulfide, and iron phosphide gradually decreased with immersion time. The presence of surface iron chloride initially increased and then decreased with immersion time. Conversely, the presence of calcium carbonate surface product initially decreased and then increased with immersion time. The content of SRB extracellular polymer, iron sulfide, and iron phosphide changed imperceptibly between 25 and 40 °C, but the overall content decreased at 60 °C. The content of surface ferric chloride remained practically unchanged between 25 and 40 °C but increased at 60 °C. The calcium carbonate surface product increased slightly with higher temperature. The corrosion of Cu-containing steel by SRB follows the cathodic depolarization theory. Full article

(This article belongs to the Special Issue Corrosion Resistance, Mechanical Properties and Characterization of Metallic Materials and Coatings, 2nd Edition)

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Review

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17 pages, 12977 KiB

Open AccessReview

Current Status of Image Recognition Technology in the Field of Corrosion Protection Applications

by Xinran Wang, Wei Zhang, Zhifeng Lin, Haojie Li, Yuanqing Zhang, Weiyin Quan, Zhiwei Chen, Xueqiang You, Yang Zeng, Gang Wang, Bolin Luo and Zhenghua Yu

Coatings 2024, 14(8), 1051; https://doi.org/10.3390/coatings14081051 - 16 Aug 2024

Cited by 1 | Viewed by 1468

Abstract

Corrosion brings serious losses to the economy annually. Therefore, various corrosion protection and detection techniques are widely used in the daily maintenance of large metal engineering structures. The emergence of image recognition technology has brought a more convenient and faster way for nondestructive [...] Read more.

Corrosion brings serious losses to the economy annually. Therefore, various corrosion protection and detection techniques are widely used in the daily maintenance of large metal engineering structures. The emergence of image recognition technology has brought a more convenient and faster way for nondestructive testing. Existing image recognition technology can be divided into two categories according to the algorithm: traditional image recognition technology and image recognition technology based on deep learning. These two types of technologies have been widely used in the three fields of metal, coating, and electrochemical data images. A large amount of work has been carried out to identify defects in metals and coatings, and deep learning-based methods also show potential for identifying electrochemical data images. Matching electrochemical images with the detection of defect morphology will bring a deeper understanding of image recognition techniques for metals and coatings. A database of accumulated morphology and electrochemical parameters will make it possible to predict the life of steel and coatings using image recognition techniques. Full article

(This article belongs to the Special Issue Corrosion Resistance, Mechanical Properties and Characterization of Metallic Materials and Coatings, 2nd Edition)

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