Thermal barrier coating (TBC) is a critical technology for hot sections of aeroengines and gas turbines. The development of TBC can significantly improve fuel efficiency and thrust-to-weight ratio of engines, allowing them to operate at higher temperatures. However, this has also led to increasingly serious high-temperature corrosion issues for TBC. High-temperature corrosion includes environmental deposition corrosion, namely CaO, MgO, Al₂O₃ and SiO₂ (CMAS) induced corrosion, molten salt corrosion, and the coupling corrosion of CMAS and molten salts, which cause premature failure of TBC and pose a serious threat to the safe operation of aero-engines and gas turbines. This paper reviews the discovery process of these corrosion problems and their reaction mechanisms with TBC at high temperatures, and summarizes the current international research progress on the corrosion-resistant TBC from two aspects, i.e., new TBC materials development and novel coating microstructure design. By comprehensively sorting out the corrosion problems and protection methods of TBC at high temperatures, the paper provides a perspective on the research direction for developing long-lifetime and corrosion-resistant TBC.

Thermal barrier coatings (TBCs) are widely used to protect the key components of areo- and land-based turbine engines, which is a key technology and an important means to improve engines efficiency and extend service life. The bond coat, as an important component of the TBC system, can relieve the thermal mismatch between the ceramic topcoat and the superalloy substrate, and improve the thermal stability of the thermal barrier coating system. On the other hand, it protects the superalloy substrate from oxidation and corrosion at high temperatures by forming a dense and continuous of Al₂O₃ layer. Therefore, the service life of the TBCs is predominantly dependent on the performance of bond coat. In this paper, the research progress on the conventional bond coat materials and preparation methods, as well as their advantages and disadvantages are introduced. The newly high-entropy alloy bond coat system is introduced with emphasis on the research progress of composition design, structure and oxidation resistance, as well as its deficiencies. Finally, the research trend of high entropy alloy bond coat materials is prospected.

Environment barrier coatings (EBC) provide effective protection from high-temperature water vapor corrosion for silicon carbide ceramic matrix composites (SiC-CMC), serving as a key material for the next-generation high-temperature components of aircraft engines. This paper reviews the preparation technology and typical structural characteristics for EBC of rare earth silicate/Si bond layer, and discusses the service failure mechanisms in high-temperature engine environments rich in water vapor and deposits CaO-MgO-Al₂O₃-SiO₂ (CMAS). Furthermore, addressing issues such as thermal mismatch of coatings, high-temperature water vapor corrosion, CMAS corrosion, and bond coat oxidation, the design and optimization methods of silicate top coats and Si bond coats are summarized from the perspectives of materials and structures. In response to the demand for even higher operating temperatures, advancements in ultra-high-temperature surface layer structure design and the development of new high-temperature-resistant bond coat materials are introduced. Finally, future research directions for high-performance environment barrier coatings are discussed.

Solid oxide fuel cell (SOFC) is a type of all-solid-state fuel cell, in which the interconnector, as a key component, significantly affects the performance of the cell. Earlier interconnects were made of ceramic materials, whose high cost and high resistance hindered the development of SOFCs. As the operating temperature of SOFCs has decreased to a range from 550 ^oC to 800 ^oC, the possibility of replacing ceramic materials with metallic alternatives has emerged. Ferritic stainless steel (FSS) has been identified as a promising candidate for interconnectors due to its low cost, good machinability and good corrosion resistance at elevated temperatures, etc. But its properties still need to be further optimized. This paper introduces the research status of SOFC interconnectors at 550-800 ^oC with emphasis on the research status of FSS and surface-modified FSS. The advantages and disadvantages of pre-oxidation and various coating-modified FSS are compared, and the potential research direction of interconnecting materials is prospected.

As a new energy transfer medium, supercritical CO₂ (S-CO₂) has shown broad application prospects in the field of energy. However, supercritical CO₂ can induce high temperature corrosion of structural metallic materials as high-temperature oxidation and carburization. The synergistic effect of corrosion and stress can aggravate the corrosion of metallic materials and deteriorate their mechanical property, accelerate their degradation, and even induce environmental cracking, all of which result in serious consequences. Therefore, this article elucidates the supercritical CO₂-induced oxidation and carburization, and their coupled effect; summarizes the methods to evaluate the environmental cracking induced by synergistic effect of corrosion and stress in high-temperature high-pressure supercritical CO₂ environments; analyzes metallic material performances under the synergistic effect of corrosion and stress, including the change of mechanical property after corrosion, stress corrosion cracking, creep, corrosion fatigue, thermal cycling and effect of surface residual stress on corrosion, etc.; and sums up the behavior and mechanisms of environmental cracking of metallic materials. It is intended to provide theoretical guidance and technical support for the material selection and environmental cracking prevention in supercritical CO₂ systems.

Al-Si coatings with different Si content were deposited on the surface of Ti-6Al-4V alloy by multi-arc ion plating, then vacuum annealing treatment of the coated alloy were carried out at different temperatures in the range 600~900 ^oC. Finally, diffused Ti-Al-(Si) coatings of different microstructure were obtained. The results showed that the diffused coatings obtained by annealing at 650 ^oC were single layer coatings mainly composed of TiAl₃. Si substituted for Al atoms in the TiAl₃ lattice and formed Ti(Al, Si)₃ solid solution. When the Si content in the coating exceeded 15% (atomic fraction), the solid solubility limit of Si in TiAl₃ lattice, Ti-Al-Si ternary compounds precipitated, forming multi-phase coating with Ti(Al, Si)₃. Penetrating cracks formed for all the single layer coatings. The diffused coatings obtained by annealing at 800 ^oC and 900 ℃ exhibited a multilayered structure, where, the outmost layer was mainly composed of TiAl₃ and Si was dissolved in the TiAl₃. When the Si content was high in the coatings, Ti-Si binary and/or Ti-Al-Si ternary compounds precipitated and the amount of the precipitates increased with the increasing of annealing temperature. Intermediate layers between the TiAl₃ layer and the Ti-alloy substrate were composed of one or two of the TiAl₂, TiAl, Ti₃Al, Ti₅Si₃ and Ti₅Si₄ layers. The multilayered structure can obviously suppress the formation of penetrating cracks on the diffused Ti-Al-Si coatings.

To improve the oxidation resistance of TiAl alloy in the thermal cycling environment, SiO₂ coating was electrodeposited on the surface of a vacuum cast γ-TiAl alloy. The cyclic oxidation behavior of the SiO₂ coating/TiAl alloy in air at 900 ^oC was studied, with each cycle consists of oxidation at 900 ^oC for 50 min and cooling to room temperature for 10 min. The failure mechanism of the electrodeposited SiO₂ coating was analyzed. Results showed that the electrodeposited SiO₂ coating can effectively improve the cyclic oxidation resistance of TiAl alloy. Furthermore, the SiO₂ coating can react with the TiAl substrate to form Ti₅Si₃ and promote the selective oxidation of TiAl to form an Al₂O₃ scale, which acts as a diffusion barrier. However, due to the thermal mismatch between the SiO₂ coating and TiAl alloy, thermal stress concentration in the coating will lead to the initiation of cracks. The cracks provide channels for the inward diffusion of oxygen and the outward diffusion of matrix elements, resulting in the generation of a large number of clusters on the surface of the oxide scale, thus destroying the continuous and dense structure of the SiO₂ coating. However, no spallation can be observed on the SiO₂ coating after cyclic oxidation for 200 h, indicating that the SiO₂ coating still maintains a certain high temperature protection ability.

Waste incineration is an alternative way of heating, which can reduce the dependence on fossil fuels and carbon dioxide emissions, but the elements such as S and Cl present in the waste incineration process affect the use of boiler pipes. With the increase of temperature, the hot corrosion phenomenon is intensified, and the hot end pipe component damage is also aggravated, which may cause catastrophic accidents. Therefore, the corrosion resistant protective coating on superheater tube is an effective method to solve this problem. The Fe-based amorphous coating (AMC) has the advantages of low cost and strong corrosion resistance: Firstly, the Fe-based AMC uses Fe-based multi-metallic materials as raw materials, which has lower cost than other kinds of amorphous materials; moreover, this kind of coating has excellent anti-corrosion, wear-resistant and easy to repair. Herein, a novel Fe-based AMC were prepared on 316L stainless steel substrate by detonation spraying technology. The corrosion behavior of AMC coating/316L stainless steel covered with deposit of 2 mg/cm² mixed salts of either K₂SO₄ + 50%Na₂SO₄ or NaCl + 50%Na₂SO₄ (in mass fraction) was assessed at 450 and 550 ^oC in air respectively. Results indicate that the coating exhibited good resistance to mixed salts corrosion superior to that of 316L stainless steel substrate. After mixed salts corrosion at 450 ^oC for 90 h, the coating showed slight corrosion and formation of minimal corrosion products. After corrosion at 550 ^oC, the coating surface became rougher with visible cracking. The corrosion impact of NaCl + 50%Na₂SO₄ on the coating was found to be more severe than that of K₂SO₄ + 50%Na₂SO₄. This is primarily due to the reaction of NaCl with the oxide layer on the coating surface; leading to the formation of Cl₂. Cl₂ can penetrate the formed oxide scale, react with the uncorroded coating, induce cracks in the oxide scale, and finally accelerate the corrosion process of the coating.

The corrosion behavior of laminated coating chromium/graphite-like amorphous carbon (Cr/GLC) on 431 stainless steel in 3.5%NaCl solution by applied hydrostatic pressures ranging 0.1 MPa to 15 MPa was investigated by in-situ electrochemical measurements, scanning electron microscopy (SEM) and secondary ion mass spectrometry (SIMS). The results showed that high hydrostatic pressure may accelerate the corrosion failure of laminated coating Cr/GLC. Hydrostatic pressure significantly increases the corrosion current density of laminated coating Cr/GLC, promotes Cl^- adsorption on the coating surface and inward to the coating/metal substrate interface, thereby decreases the interface bonding strength of coating/metal substrate.

Eutectic high-entropy alloy, YHf-AlCoCrFeNi_2.1 (YHf-EHEA) was prepared using vacuum arc melting, and then the YHf-EHEA was surface modified via Pt electroplating and followed by a diffusion treatment at 1080 ^oC also in vacuum, then after, the Pt-modified alloy maned as YHfPtAlCoCrFeNi_2.1 (YHfPt-EHEA). Afterwards, the hot corrosion behavior of the two EHEAs in mixed salts Na₂SO₄/K₂SO₄ (mass fraction 75%:25%) at 800 ^oC and Na₂SO₄/NaCl (mass fraction 75%:25%) at 900 ^oC respectively was assessed by means of XRD, SEM and EPMA. The results indicate that the oxide scale formed on YHf-EHEA peeled off in a large area due to hot corrosion in Na₂SO₄/K₂SO₄ at 800 ^oC, while the oxide scale formed on YHfPt-EHEA remains intact and continuous in the same hot corrosion situation. During hot corrosion in Na₂SO₄/NaCl mixed salt at 900 ^oC, O and S diffuse rapidly into YHf-EHEA and form a number of oxides and sulfides within the alloy, which accelerate the cracking and peeling behavior of oxide scale. In contrast, after being Pt-modified the YHfPt-EHEA exhibits significant inhibition effect to the inward diffusion of O and S into the alloy, and therewith suppresses the hot corrosion process.

Aluminized coating was prepared on the surface of nickel-based superalloy K444 by chemical vapor deposition (CVD) technique. The corrosion behavior of K444 alloy without and with CVD aluminized coating beneath a thin deposits film of 95%Na₂SO₄ + 5%NaCl was studied in air at 850 and 950 ^oC. The results indicate that K444 alloy showed poor corrosion resistance after 10 h corrosion. A scale of loose mixed oxides was formed on its surface, of which the outer layer is mainly composed of Cr₂O₃ and TiO₂, and the inner layer is Al₂O₃. With the increase of temperature, the corrosion was intensified and the spallation occurred of the corrosion products scale. In contrast, a protective Al₂O₃ scale was formed on the surface of the CVD aluminized coating, which effectively improves the corrosion resistance for the K444 alloy.

The performance variation of a typical fluoroelastomer FX-17 due to hot air aging at 160, 180, 200, 220 and 240 ^oC, respectively was assessed, in terms of its hardness, compressive permanent deformation rate, tensile strength, elongation at break and other parameters. The corresponding change of its molecular structure were characterized by means of Fourier infrared spectroscopy and other methods. Based on Arrhenius empirical formula, the model of performance decay and life degradation of fluoroelastomer FX-17 was also established. The results show that after being hot air aged, the maximum change range of Shore hardness increased from the initial value of 79 HA to 92 HA, the maximum change range of compressive permanent deformation rate increased to 116% of the initial value, and the maximum change range of tensile strength decreased from the initial value of 15 MPa to 8 MPa. The maximum change range of elongation at break decreased from the initial value of 199% to 125%. In the process of aging in hot air, the dehydrofluorination of large molecules of FX-17 mainly occurs, which leads to a chain reaction of free radical aging. When the compression permanent deformation rate is used as the evaluation index of the sealing failure of typical fluoroelastomer FX-17, its service life can reach more than 2700 h at 200 ^oC.

Al-diffusion coatings composed primarily of δ-Ni₂Al₃ phase were developed on DD6 single-crystal nickel-based superalloy and pure nickel via chemical vapor deposition (CVD) technique at 750 ^oC, respectively. Results of oxidation in air at 1000 ^oC revealed that the CVD aluminide coating on DD6 superalloy presented higher oxidation rate rather than its counterpart on Ni. Photo-luminescence spectroscopy analysis indicated that during the early oxidation stage a single Al₂O₃ scale could formed on the two CVD aluminide coatings; however, there was a significant enhancement in the spectrum intensity of metastable θ-Al₂O₃ within the alumina scale on DD6 superalloy. It is proposed that elements from DD6 superalloy diffused into the alumina scale during oxidation, thereby influencing the oxidation rate by prolonging the transformation period of θ-Al₂O₃ into stable α-Al₂O₃ and promoting Al³⁺ outward diffusion for oxide growth.

Three enamel coatings with identical total quantities of flux Na₂O, K₂O, and B₂O₃, but varying B₂O₃ mass fractions (11.78%, 14.78% and 17.78%) were prepared on on T92 ferritic steel. Their corrosion behaviorwas studied in molten salts MgCl₂-NaCl-KCl at 600 ^oC in air. Results show that the corrosion severity of the enamel coatings gradually decreases with the increasing amount of B₂O₃ in enamels. After corrosion for 500 h, the enamel coating with the lowest mass fraction of B₂O₃ (11.78%) suffered from a thickness loss of about 82 μm and a mass loss of about 14.44 mg/cm² under the combined action of physical dissolution and chemical attack of corrosive salts. Meanwhile, under the action of continuously generated gaseous corrosion products inside the coating, the coating was swelled, as a result, its thickness is expanded from 82.7 ± 0.5 μm of the original to 253.9 ± 44.9 μm. By increasing B₂O₃ content to 14.78%, the thickness- and mass-loss of the enamel coating were significantly reduced to about 12 μm and 3.69 mg/cm² respectively, while the volume expansion caused by rapid corrosion is eliminated. Comparatively, the enamel coating with the highest mass fraction of B₂O₃ (17.78%) showed excellent corrosion resistance with a thickness loss of less than 1 μm, and mass loss is eventually reduced to only 0.16 mg/cm².

Due to the excellent neutron absorption properties, cold-sprayed B₄C/Al composite coating shows a good application prospect in the field of spent fuel storage. However, there are few studies on the corrosion behavior of cold-sprayed B₄C/Al coating in boric acid solution. In this paper, the corrosion behavior of cold-sprayed B₄C/Al coating coated 316L stainless steel in boric acid solution was studied by immersion test, electrochemical workstation, and EIS as well as SEM + EDS and XRD. Results show that the interface between B₄C particles in the cold-sprayed coating is weak, and the boric acid solution tend to preferentially corrode along the interparticle interface, thus results in the corrosion of the coating matrix. Post heat treatment can effectively improve the structure of cold sprayed B₄C/Al coating and enhanced interfacial bonding between particles. As a result, the corrosion resistance of B₄C/Al coating in boric acid solution was improved.

Ni-based single crystal superalloys have been widely used as materials for aircraft engine turbine blades due to their excellent high-temperature mechanical properties. The harsh service environment can lead to severe oxidation of the superalloys for turbine blades. In contrast to the high-temperature mechanical properties, further research is needed on the oxidation behavior of the Ni-based single crystal superalloys. Herein, the evolution mechanism of the oxide scale on Ni-based single crystal superalloy has been studied through first-principles calculations and oxidation experiments. By analyzing the interface adhesion energy and charge distribution, while taking the impact of O and Al atoms on the interface stability into account, it is determined that the Al-O structure has been identified as the most stable NiAl/NiO interface model. The aggregation of O and Al atoms at the interface may weaken the bonding strength of the NiAl/NiO interface, which means that the interface tends to be separated easily. The oxidation behavior of the alloy was examined using XRD, EDS, SEM, etc., in terms of the oxidation kinetics of the alloy, as well as the morphology and phase composition of the oxide scales. Results indicate that NiO forms initially during the alloy oxidation, followed by Al₂O₃ beneath NiO. As O and Al atoms aggregate at the interface, NiO tends to separate from the alloy surface. By combining first-principles calculations with the oxidation test results, the mechanism of evolution of the oxide scale on the alloy was ultimately elucidated.

The corrosion behavior of pre-oxidized GH4169 alloy beneath a solid NaCl deposit film in flowing water vapor containing O₂ at 600 ^oC was investigated by means of oxidation kinetics measurement, scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscope (TEM) in the aspects of corrosion kinetics, morphology and phase composition of corrosion products. The results indicate that a continuous oxide scale composed mainly of Cr₂O₃/Nb₂O₅ was formed by pre-oxidation of GH4169 alloy in air at 1000 ^oC for 2 h. However, after 5 h corrosion in the above designed conditions, the pre-oxidized GH4169 alloy underwent serious corrosion, while the pre-formed oxide scale was seriously damaged, and the corrosion product scale mainly composed of NiFe₂O₄, NaNbO₃, Na₂CrO₄ and residual Cr₂O₃ was formed. Finally, the corrosion mechanism of the pre-oxidized GH4169 alloy beneath a solid NaCl deposit film in flowing water vapor containing O₂ at 600 ^oC was discussed in detail, in terms of the deterioration process of the pre-oxidation scale.

Herein, An amorphous coating of FeCrMoBSi (namely Fe-18%-20%Cr, 7%-8%Mo, 5%-6%Si and 4%-5%B, in mass fraction) on 310S stainless steel was prepared by high velocity oxy-fuel (HVOF) spraying technique. The corrosion resistance in 3.5%NaCl solution and friction-wear performance before and after heat treatment, as well as the effect of heat treatment on the crystallization behavior for the as prepared amorphous coating were studied. The results indicated that the amorphous coating exhibited excellent corrosion resistance in 3.5%NaCl solution, characterized by the low porosity (2.45%) and the high Cr₂O₃ content (76.51%) in the as prepared coating, which can effectively protect the substrate. However, after being post heat-treated, numerous pores and cracks emerged in the coating, which can act as short-circuit diffusion channel for the corrosive media, leading to poor corrosion resistance. Results of friction- and wear-testing indicated that the as prepared amorphous coating exhibited the lowest wear volume and wear rate (1.784 × 10^-5 mm³/(N·m)). Although, for the post heat-treated coatings, the wear volume and wear rate increase slightly with the increasing heat treatment temperature.

The stripping and refurbishment of single-phase (Ni, Pt)Al coating after oxidation for different times was investigated, especially in terms of the microstructure evolution of coating and substrate. The (Ni, Pt)Al coating was prepared on a Ni-based single crystal superalloy N5 firstly via electro-deposition of a thin Pt-film and followed by above-pack aluminizing. Afterwards, the prepared (Ni, Pt)Al coating/N5 alloy was oxidized in air at 1100 ^oC for 300, 1000 and 3000 h, respectively, where in all cases Al₂O₃ was the exclusive oxide product on all the test coatings. Moreover, with the increase of oxidation time, the coating degraded severely and coarse TCP precipitates emerged out beneath the coating. The (Ni, Pt)Al coatings after oxidation for various times were successfully removed with mixed solution of HCl and C₆H₈O₇·H₂O. Finally, a fresh (Ni, Pt)Al coating was refurbished again on the alloy of the deteriorated coating being removed. During the stripping with mixed acids, the dissolution of coating is mainly ascribed to corrosion of grain boundaries, while the dissolution rate decreases with the reduction of Al-content. However, the microstructure of the refurbished (Ni, Pt)Al coating is little different from those prepared on the as received alloy, nevertheless, it is observed that the coarse precipitates of TPC phase emerged on the alloy side after long time oxidation.

The oxidation behavior of Super304H austenitic stainless steel in 605 and 640 ^oC, 26 MPa supercritical water for 2000 h was studied by intermittent weighing method. The mass change caused by oxidation in supercritical water was measured by electronic balance. The morphology, elemental composition and phase types of the oxide scales were examined by field emission electron microscope, energy spectrometer, X-ray diffractometer and X-ray photoelectron spectrometer. The results show that the oxide scale spalling occurs during the oxidation process. Nodular iron-rich oxides formed on the steel surface at the initial oxidation stage. With the increase in oxidation time, the iron-rich oxides gradually covered the whole surface of the test steel. The oxide scale was composed of a double layered structure, the outer layer rich in Fe and the inner layer rich in Cr. The temperature and oxidation time affect the phase composition of iron-rich oxides. A thin Cr-rich oxide layer can be observed at the oxide scale/substrate interface, which has an important impact on the oxidation resistance of Super304H. The results provide data support for the accurate evaluation of the oxidation resistance of Super304H stainless steel to supercritical water.

High entropy alloy (HEA) of Al_0.21Co_0.17Cr_0.13Fe_0.11Ni_0.18Si_0.20 (atomic fraction) was fabricated by means of laser melting deposition (LMD) technique. The prepared alloy consists of a single body-centered-cubic (bcc) phase, and its grain size gradually refined as the laser power decreased from 900 W to 700 W. The bcc HEAs obtained at various laser powers were subjected to isothermal oxidation at 1100 ^oC in either dry air or wet air (air + 10%H₂O (volume fraction)), respectively. There were several observations: all HEAs had the ability to thermally develop a protective scale of Al₂O₃ in both dry and wet airs; the decrease in grain size favored the formation of Al₂O₃ scale with a slower growth rate; the presence of H₂O vapor accelerated the growth rate of Al₂O₃ scale. Finally, the above findings were discussed and interpreted.

Based on the first-principles calculation method, the influence of B addition on the oxidation behavior of compound pair MoSi₂/MoB was comprehensively investigated. The results showed that the oxygen adsorption energy at the interface of compound pair MoSi₂/MoB, and of the compound MoB itself is lower and the diffusion activation energy of oxygen atom passing through the interface MoSi₂/MoB is also lower, which may facilitate the rapid oxidation of the compound surface during the initial oxidation stage and enable the rapid formation of a protective oxide scale. When the oxidation process reached a stable state, a scale of borosilicate with 6%B (atomic fraction) may form on the compound surface with the lowest oxygen diffusion coefficient, namely, excellent oxidation resistance of the oxide scale. Therefore, precise control of B-doping is a promising strategy for designing MoSi₂-based compound Mo-Si-B of high oxidation resistance.

The effect of Cr- and Si-addition on the oxidation behavior of N80 carbon steel for gas injection well tubing was investigated at 450-650 ^oC in a laboratory made oxidation atmosphere, with the aim to simulate the combustion flame products during the oil field fire-flooding process is adopted for oil production. The results showed that the addition of 3%Cr and 5%Cr (mass fraction) respectively may facilitate the steel to form a thick oxide scale composed of Fe₂O₃ and (Fe, Cr)₃O₄, and the oxide scale underwent serious flaking, while the simultaneous addition of 0.5%Si and 5%Cr can not only improve the oxidation resistance of the steel but also significantly inhibit the flaking of the oxide scale, and the addition of 9%Cr may favor the formation of a protective Cr₂O₃ scale. Furthermore, CrS was found in the inner oxide scale of the N80 steel with the simultaneous addition of 0.5%Si and 5%Cr, while no obvious CrS was found with the addition of 9%Cr. Therefore, the addition of alloying elements Cr and Si can significantly improve the oxidation resistance of N80 carbon steel tubing for gas injection wells.

Combustion accelerant is a kind of highly flammable, volatile, and easily polluted substance, which is difficulty to extract and identify in the fire scenes. In order to solve the issue of identifying the accelerant, a liquid combustion atmosphere simulation system was developed in the Lab to simulate the fire environment involving ethanol accelerant. Herein, the oxidation behavior of 304 stainless steel was studied via the Lab simulation system in the combustion atmosphere of air-ethanol at 600-800 ^oC in terms of the corrosion kinetics, the composition and morphylogy of corrosion products, and the steel microstructure variations. The resuts show that the oxidation behavior of 304 stainless steel in the ethanol combustion atmosphere differ significantly from that in air, making it impossible to form a continuous protective oxide scale on its surface and thus catastrophic oxidation occurs. The surface oxide scale is composed of island-like oxide clusters of Fe₂O₃ and Fe₃O₄. Furthermore, oxidizing atmosphere induced by ethanol flux combustion along with turbulence will accelerate the chromium consumption from the steel, as well as enhanced the separation of oxide scale. Besides the oxidation rate also increases with the increasing test temperature. It follows that the above findings may be helpful to identify if there existed or not accelerant components in the fire scenes.

It is often noted that there exist a number of residue water-stains on the alloy surface after removing carbon deposits on TC4 Ti-alloy surface by alkaline-washing and subsequent high-temperature water-washing, which can seriously interfere the subsequent fluorescence analysis. Herein, the electrochemical corrosion behavior of TC4 alloy in 10% (mass fraction) NaOH solution at various temperatures is assessed via electrochemical workstation, optical microscopy and SEM+EDS, aiming in understanding the formation mechanism of the residue water stains during the removal process of carbon deposits. The results show that with the increasing alkaline solution temperature, the corrosion rate of TC4 alloy accelerates.Results of OM and SEM+EDS characterization show that the emerge of residue water-stains may be closely originated from spots where the existing passivation film was corroded by the concentrated residue alkaline solutions on the alloy surface. Furthermore, after being cleaned with alkali solution of the test parts of the alloy, then they are comparatively cleaned with deionized water and tap water respectively. It shows that with the increase of water temperature, the residue water-stains can be clearly observed on the surface of the test parts. Fortunately, the utilization of deionized water instead of tap water can effectively avoid the occurrence of the residue water-stains.