High Temperature Corrosion Mechanisms Research Articles

Microstructure, mechanical and oxygen-deficient lead-bismuth eutectic corrosion properties of FeCrAlTiMo high-entropy alloy coatings for fuel claddings

The FeCrAlTiMo high-entropy alloy (HEA) coatings were deposited on the ferritic/martensitic (F/M) steel fuel cladding tubes by magnetron sputtering technology to improve their lead-bismuth eutectic (LBE) corrosion resistance. The effects of bias voltage on the microstructure, mechanical and LBE corrosion properties of the FeCrAlTiMo coatings were systematically investigated. The LBE corrosion test shows that the coatings with a bias voltage of −150 V exhibit the best oxidation resistance after exposed to the oxygen-deficient LBE at 600 °C for 500 h, and can be used as a protective candidate coating material for lead-cooled fast reactor (LFR) application. The high-temperature LBE corrosion mechanism of the FeCrAlTiMo coatings under deficient oxygen concentration was also discussed in detail.

Thermal Corrosion Properties of Composite Ceramic Coating Prepared by Multi-Arc Ion Plating

In this study, a NiCr/YSZ coating was applied to a γ-TiAl surface using multi-arc ion plating technology to enhance its high-temperature performance and explore the mechanisms of high-temperature oxidation and thermal corrosion. The thermal corrosion properties of the γ-TiAl matrix and NiCr/YSZ coating were investigated at 850 °C and 950 °C using a constant-temperature corrosion test in a 75% Na2SO4 + 25% NaCl mixture. The results indicate that after 100 h, the thermal corrosion weight gain of the coating samples was 70.1 mg/cm2 at 850 °C and 118.2 mg/cm2 at 950 °C. At these temperatures, sulfide formation on the surface increases, leading to a loose and porous surface. After 100 h of high-temperature corrosion at 850 °C, the primary oxidation product on the surface of the coating was tetragonal-ZrO2. At 950 °C, Y2O3, which mainly acts as a stabilizer in YSZ, reacted with Na2SO4, resulting in the continuous consumption of Y2O3. This reaction caused a substantial amount of tetragonal-ZrO2 to transform into monoclinic-ZrO2, altering the volume of the ceramic layer, which induced internal stress, crack propagation, and minor spallation. A continuous and dense internal thermally grown oxide (TGO) layer effectively impeded the diffusion of molten salt substances and oxygen, thereby significantly improving the thermal corrosion resistance of the thermal barrier coating.

Corrosion behavior and mechanism of Inconel 625 coatings in high-temperature acidic environments for waste incineration applications

This study explores the high-temperature corrosion behavior and mechanisms of laser-clad Inconel 625 coatings applied in waste incineration environments. Inconel 625 coatings were deposited on a substrate using laser cladding technology, and corrosion tests were performed in various high-temperature acidic environments. The coatings were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and laser confocal microscopy to investigate their microstructure, composition, and corrosion products. The findings indicate that corrosion weight gain was most pronounced in HCl environments at 800 °C and HBr environments at 600 °C, underscoring the critical influence of temperature and acidity on reaction kinetics. Moreover, the corrosion morphology was closely tied to the environment, with distinct patterns observed: pitting in HCl, nodular growth in H2SO4, and cracking and spalling in HF and HBr environments. High temperatures promoted oxidation reactions, resulting in the formation of a dense oxide layer predominantly composed of Cr2O3 and NiCr2O4, which offered some degree of protection. However, pitting and cracking in acidic environments suggested that the protective oxide layer's effectiveness was compromised under extreme conditions. This study provides a comprehensive understanding of the corrosion behavior and mechanisms of Inconel 625 coatings in various acidic environments and high temperatures within waste incineration applications. It offers valuable insights into the impact of temperature and different acidic media on corrosion rates and morphologies, laying the groundwork for predicting the service life and developing protective strategies for these materials in industrial settings.

High-temperature corrosion mechanisms of a Ni-based alloy in simulated multi-source organic waste co-incineration environments

Due to the new trend of co-incinerating municipal solid waste (MSW) with sewage sludge, medical waste, or industrial organic waste to attain a “waste-free” status, mixing of multi-source organic wastes (MSOW) increases the complexity of solid waste, which fluctuates the composition of corrosive species in the boiler. The fluctuation of corrosive species alters the alkali metals/S/Cl ratios and increases the uncertainties of high-temperature corrosion of boiler key components. The corrosion behaviors and mechanisms in varying compositions of corrosive species are complex and remain elusive. To investigate the corrosion characteristics during the co-incineration of MSOW, this study examined the corrosion mechanisms of a nickel-based Ni59.08Cr24.31Al10.74W5.3B0.57 alloy in simulated co-incineration environments of MSOW. The environment contained either HCl, NaCl, or SO2 in wet oxygen at 600 °C. For each case experiment, the maximum possible value of each corrosive species expected in the actual incinerator and/or its absence was considered. HCl of either 0 or 1500 ppm, SO2 of 0 or 300 ppm, and NaCl of 0 or 50 mg/cm2 were systematically used in each experiment. The influence of each corrosive condition on the corrosion of the alloy was evaluated by mass gain measurements, and the corrosion mechanisms were elucidated through SEM, EDS mapping, XRD, XPS analyses, and thermodynamic equilibrium calculations. The results revealed that NaCl salt and HCl gas in wet oxygen have complementary effects, which accelerated the corrosion of alloy, reaching ∼ 65.6 mg/cm2 over one week. HCl enhanced the corrosion by affecting the chemical reactions that regenerated NaCl, which participated in prolonged corrosion processes. SO2 reduced the mass gain of the alloy to 38.4 mg/cm2. SO2 participated in the sulfation of NaCl, forming a mixed layer of Na2SO4 and (Al/Cr)2O3, reducing the mass gain by 1.71 times. In the environment without NaCl, SO2 helped in the formation of a protective oxide layer, which prevented HCl from reaching the alloy, reducing the corrosion impact by 23.5 times.

High temperature corrosion behavior and mechanism of steel slag-based glass ceramic in the eutectic carbonates

Steel slag-based glass ceramic for thermal energy storage was first fabricated by quenching method, and then their high temperature corrosion behavior in the eutectic carbonates and related mechanism have been investigated using X-ray diffraction，Raman spectroscopy and scanning electron microscope techniques. The results show that holding time has a significant influence on the corrosion layer thickness at 800oC. As the holding time was extended, the thickness of the corrosion layer with obvious cracks tended to increase. Further EDS analyses disclosed that the divided corrosive layers along the extended directions of the cracks should be similar in both the compositions and microstructure. Based on these observations, the possible corrosion mechanism was discussed after defining phase structure of nonstoichiometric (Fe0.35Al0.20Mg0.44) Ca0.96(Fe0.08Si0.70Al0.20)2O6.12 as a combined system of CaMgSi2O6(Di)-CaFe3+AlSiO6(Es)-CaAl2Si2O8(An). Oxygen offered by the molten carbonates salt is regarded to play a critical role in the corrosion process. In an atmosphere rich in oxygen, both Na+ and K+ ions diffused into the diopside can replace Ca2+ and Mg2+, etc. resulting in polyhedral structural reorganization for electrical neutrality. On the other hand, the bonding stability of the cation-oxygen bonds in diopside was proved to be weaker than that in single oxides. These two aspects contribute to the continuous dissolution of Ca2+ and Mg2+, etc. in the molten carbonates salt.

Corrosion of Ni-based alloy coatings prepared by laser cladding in high-temperature chloride environment

Due to the complex incineration environment of waste incineration power generation boilers generates large amounts of acidic gases (such as Cl2 and HCl) and alkali metal chlorides (such as NaCl and KCl), leading to boiler corrosion failure. Herein, a new type of NiCrAlTi alloy coatings was deposited on 304 stainless steel surfaces by laser cladding technology. High-temperature corrosion experiments were then carried out at 650 °C for 64 h and the results were compared with those of traditional Inconel625 alloy coating. The high-temperature chloride corrosion mechanism and the corrosion resistance of alloy coatings were examined. The results revealed the decomposition of chlorides, such as HCl, NaCl, and KCl into Cl2 at high temperatures as the source of corrosion of high-temperature chlorides. The released C12 reacted with the metals present in the coating to form nonprotective metal chlorides. The low melting point and high vapor pressure of metal chlorides allowed their transition into a gaseous state to diffuse outward and oxidize into Cl2. In turn, the released Cl2 reacted with the metal to induce corrosion. During the corrosion process of NiCrAlTi alloy coating, a Cr depletion zone was induced, and a continuous Al2O3/TiO2/Cr2O3 three-layer protective film was formed on the coating surface, conducive to better alleviating the corrosion caused by the reaction between Cl2 passing through the film and the metal substrate. Under the conditions of this experiment, the corrosion resistance of NiCrAlTi alloy coating is 1.8 times that of the common material 304 stainless steel, and about 1.2 times that of Incon625 alloy coating. With the extension of the experiment, its corrosion resistance will be better. Overall, rich experimental data and theoretical guidance were provided for further research and development on high-temperature chloride corrosion-resistant alloys or coating materials for high-efficiency cost-effectiveness boilers.

High-temperature corrosion of a Si3N4/W composite exposed to molten MgCl2-NaCl-KCl salts

The high-temperature corrosion behavior of a Si3N4/W composite under the molten MgCl2-NaCl-KCl salts has been investigated. It is suggested that the molten salts diffuse along the physical surface defects and enter the interior of adjacent Si3N4/W grains, leading to the 9.1% bending strength loss after 400 hours for corrosion. In air atmosphere, oxidation products WO2, WO3, and corrosion product MgWO4 caused a 34.3% bending strength decrease after 400 hours for corrosion. This study elucidates the high-temperature molten chloride salt corrosion mechanisms of the Si3N4/W composite material under two different atmospheres. The composite demonstrates relatively excellent corrosion resistance in service environments.

Correction: High-Temperature Oxidation and Hot Corrosion Behaviors and Mechanism of One Typical Aero-Engine Material 0Cr18Ni9 by One Novel Superhydrophobic and Oleophobic Ultrafine Dry Powder Extinguishing Agent

Correction: High-Temperature Oxidation and Hot Corrosion Behaviors and Mechanism of One Typical Aero-Engine Material 0Cr18Ni9 by One Novel Superhydrophobic and Oleophobic Ultrafine Dry Powder Extinguishing Agent

High-temperature dynamic corrosion mechanisms of austenitic stainless and carbon steels in nitrates for concentrating solar power

Abstract: In this paper, to simulate the dynamic corrosion mechanisms of metals exposed to a high-temperature molten salt mixture of NaNO3–KNO3, the experimental samples made of commonly used stainless steel alloys such as 304 (with/without welds) and Q275 were suspended, along with stirring blades, in a specially designed stirred kettle to obtain their corrosion characteristics. For the experimental samples, the Q275 surface exhibited significant quantities of Fe3O4 and Fe2O3, while 304 generated FeCr2O4, Cr2O3, and MgFe2O4 with protective effects. The microstructure of the welding zone in 304 exhibited considerable disparities compared to that of the base material, consequently leading to augmented susceptibility towards localized corrosion. The uneven distribution of chromium in the welding zone resulted in intergranular corrosion and alterations in the crystal structure. Moreover, experimental studies have demonstrated that NO3- in the molten salt undergoes decomposition to generate oxygen ions, which contribute to the corrosion reaction. Notably, under all test conditions, the corrosion rate of samples exhibited the following ranking: 304 (without welds) < 304 (with welds) < Q275.

High-Temperature Oxidation and Hot Corrosion Behaviors and Mechanism of One Typical Aero-Engine Material 0Cr18Ni9 by One Novel Superhydrophobic and Oleophobic Ultrafine Dry Powder Extinguishing Agent

High-Temperature Oxidation and Hot Corrosion Behaviors and Mechanism of One Typical Aero-Engine Material 0Cr18Ni9 by One Novel Superhydrophobic and Oleophobic Ultrafine Dry Powder Extinguishing Agent

High-temperature corrosion of phosphate completion fluid and corrosion inhibition method by membrane transformation

By analyzing the corrosion of phosphate completion fluid on the P110 steel at 170 °C, the high-temperature corrosion mechanism of phosphate completion fluid was revealed, and a corrosion inhibition method by membrane transformation was proposed and an efficient membrane-forming agent was selected. Scanning electron microscope (SEM) images, X-ray energy spectrum and X-ray diffraction results were used to characterize the microscopic morphology, elemental composition and phase composition of the precipitation membrane on the surface of the test piece. The effect and mechanism of corrosion inhibition by membrane transformation were clarified. The phosphate completion fluid eroded the test piece by high-temperature water vapor and its hydrolyzed products to form a membrane of iron phosphate corrosion product. By changing the corrosion reaction path, the Zn2+ membrane-forming agent could generate KZnPO4 precipitation membrane with high temperature resistance, uniform thickness and tight crystal packing on the surface of the test piece, which could inhibit the corrosion of the test piece, with efficiency up to 69.63%. The Cu2+ membrane-forming agent electrochemically reacted with Fe to precipitate trace elemental Cu on the surface of the test piece, thus forming a protective membrane, which could inhibit metal corrosion, with efficiency up to 96.64%, but the wear resistance was poor. After combining 0.05% Cu2+ and 0.25% Zn2+, a composite protective membrane of KZnPO4 crystal and elemental Cu was formed on the surface of the test piece. The corrosion inhibition efficiency reached 93.03%, which ensured the high corrosion inhibition efficiency and generated a precipitation membrane resistant to temperature and wear.

High-temperature corrosion mechanism analysis of 310S alloy in typical MSWI flue gas environment at 460–580 °C

High-temperature corrosion mechanism analysis of 310S alloy in typical MSWI flue gas environment at 460–580 °C

Study on chemical corrosion properties of titanium alloy in 2A14 aluminum melt

Titanium alloy radiation rods have excellent physical and chemical properties compared to other materials, and are commonly used for ultrasonic casting of 2A14 aluminum alloy. However, titanium alloys are chemically corroded in high-temperature aluminum melts for a long time, making it difficult to precisely regulate the elemental composition during casting. In order to better understand the high-temperature chemical corrosion mechanism of titanium alloy radiation rods, this research looks into the corrosion morphology, weight loss, surface roughness, and reaction layer. The study’s findings suggest that the rate of chemical corrosion of titanium alloy in high-temperature aluminum melt is often inversely correlated with the degree of roughness, with the degree of roughness changing nonlinearly during the corrosion process. Titanium alloy weight loss rates with roughness Ra0.4 μm, Ra7.2 μm, Ra9.5 μm and Ra9.8 μm are 0.16 mg per min, 0.25 mg per min, 0.37 mg per min and 0.29 mg per min, respectively. The corrosion product of the chemical corrosion process is TiAl3, which is granular. Under varying roughness conditions, the solid-liquid interface of Al/Ti emerges reactants after 4 min, and the TiAl3 reaction layer arises after 12 min. Furthermore, the reaction layer with little roughness is flat and compact, whereas the reaction layer with great roughness is loose and contains many faults. At the same time, the growth rate of the reaction layer decreases slightly. And the greater the surface roughness, the greater the TiAl3 reaction layer grows at the titanium alloy matrix.

An Accelerated-Based Evaluation Method for Corrosion Lifetime of Materials Considering High-Temperature Oxidation Corrosion

In the realm of industrial automation, corrosion represents one of the primary modes of failure, especially in the case of armored thermocouples exposed to temperatures ranging between 1073.15–1373.15 K. In this context, the selection of metal materials that can withstand high-temperature oxidation and corrosion is of paramount importance. Typically, the corrosion resistance of a given metal material is assessed by measuring the “annual corrosion rate” or “corrosion depth”, which can provide an estimated life expectancy value. However, such an approach fails to account for the individual characteristics of the material, and thus does not conform to objective laws. Rather, the corrosion life of a batch of metallic materials should follow the Weibull distribution, or possibly a normal distribution, as per recent studies that have examined the high-temperature oxidation corrosion mechanism of machine or core components. This investigation effectively combines the standard approach for evaluating metal corrosion resistance in the field of materials with the method of assessing component life in the domain of reliability. Furthermore, we consider the individual differences among materials and provide the life distribution function of metals in corrosive environments and thereby refine the evaluation of metal corrosion resistance. This study ultimately establishes a thermocouple accelerated life evaluation model that enhances the accuracy and efficiency of life evaluations for related products.

Understanding high-temperature corrosion behavior of an AlN/Mo functionally graded material exposed to Li/LiF-LiCl-LiBr vapor

The high-temperature corrosion behavior of an AlN/Mo functionally graded material (FGM) under the Li/LiF-LiCl-LiBr vapor has been investigated. It is suggested that the Li vapor diffuses along the AlN and AlN/Mo grain boundaries and enters the interior of adjacent AlN grains, leading to the disintegration of AlN grains and subsequent failures. The 3D Mo networks are barely corroded, thus preventing cracking that may occur due to the inconsistent deformation inside the FGM. This work unravels the high-temperature corrosion mechanisms for the AlN/Mo FGM. Meanwhile, the operating temperature threshold for the liquid metal batteries employing Mo/AlN/Mo seals is determined to be ∼ 600 °C.

High-temperature corrosion data and mechanisms for T122, Super304H and HR3C after 15 years in 1000MW ultra-supercritical power plant

ABSTRACT The high-temperature corrosion of heat-resistant steels T122, Super304H and HR3C used for the inlet of a header in a 1000 MW ultra-supercritical power plant for 15 years was investigated. The steam temperature and pressure were about 610 °C and 28 MPa, respectively. The morphology and phase compositions of the corrosion products formed on the investigated tubes were analysed using X-ray diffraction and a scanning electron microscope with an energy dispersive spectroscopy detector. The results showed that the thickness of the corrosion products on the tube fireside was larger than that on the steam-side of the investigated tubes, which was due to the sulphur in the flue gas. The thickness rank of the corrosion products on the investigated steels was T122 > Super304H > HR3C. Defects including micro-cracks and voids were found in the corrosion products on both sides of the three tubes, which led to the breakaway of corrosion products.

High temperature corrosion mechanism of Ni–5W–6B–28Cr–13Al alloy in simulated MSW incineration environment

In this study, the corrosion behavior of a newly designed alloy (Ni–5W–6B–28Cr–13Al) in simulated municipal solid waste (MSW) incineration atmosphere in the presence of HCl, NaCl, and SO2 under an oxidizing humidity condition at 600 °C was conducted. The combined effects of these aggressive species on corrosion mechanism were elucidated by means of XRD, SEM, EDS, and thermodynamic calculations. The results showed that the contribution to the corrosion rate was in the order of NaCl + HCl > NaCl > HCl. The alloy was rarely corroded without NaCl coating, while the alloy experienced enhanced corrosion attack of 12.183 mg/cm2 under NaCl exposure. In the presence of HCl and NaCl, the accelerated corrosion of the tested alloy reached a maximum mass gain of 75.592 mg/cm2. Both experimental and theoretical results suggested that the corrosion occurred via an active oxidation reaction where the NaCl coating was converted to molten phase which degraded the alloy forming a massive unprotective oxide scales. Nonetheless, the synergistic effect of NaCl and HCl was significantly suppressed by the sulfation after SO2 application of nearly 50% less than the mass change before SO2 application.

Effect of Alkyl Chain Length on High-Temperature Corrosion Inhibition Behavior and Mechanism of Imidazole Ionic Liquids: An Experimental, Density Functional Theory and Molecular Dynamics Simulation Study

Effect of Alkyl Chain Length on High-Temperature Corrosion Inhibition Behavior and Mechanism of Imidazole Ionic Liquids: An Experimental, Density Functional Theory and Molecular Dynamics Simulation Study

The high temperature wetting and corrosion mechanism analysis of Nb by TiAl alloy melt

High temperature corrosion behavior of Nb containing a TiAl melt is studied connecting with grain boundary wetting (GBW). Three intermetallic compounds (IMC) layers are formed and corroded step by step via the TiAl melt. The interfacial morphology and wetting angle evolution are investigated theoretically and experimentally. The morphology of the grooves controlled by interfacial tension, while nonzero wetting angles θd controlled by surface diffusion are established at the roots. By quantitative assessment, when θd is more than 140°, the grooves terminating on a thin sheet, which is responsible for the effective inhibition of further wetting and corrosion.

Study on high temperature corrosion mechanism of water wall tubes of 350 MW supercritical unit

The water wall of a 350 MW supercritical unit was severely corroded at high temperature in a short period. An analysis was made on the mechanism of high temperature corrosion of the water wall by chemical analysis, metallographic examinations, mechanical property test, and SEM observation. The results show that high temperature corrosion has no obvious effect on the material properties, and the main failure form is the reduction of tube wall by corrosion. Through the structure and composition analysis of corrosion products, it is found that there are three corrosion product layers on the outer wall of the water wall. Lots of holes existed between the corrosion product layer and the matrix, which made the corrosion product is easy to be spalled. The sulfur content in the corrosion product increases gradually from inside to outside, which proves that sulfur is the main factor affecting the high temperature corrosion of the water wall.