To further understand the influencing factors of oil stains induced by rust-preventive oils on metal surfaces and their comprehensive prevention and control methods，rust-preventive oil stain tests were carried out to systematically evaluate the oil stain tendency of different types of rust-preventive oil additives on carbon steel surfaces.The results showed that formulations containing unsaturated fatty acid-type rust inhibitors are prone to oil stain formation，while calcium/barium sulfonates，saturated fatty acid derivatives，and film-forming agents with good stability have relatively low oil stain risk.The research further revealed that the formation mechanism of oil stains is the result of the synergistic effect between local microbattery effect and oxidative side reactions；an increase in moisture content will aggravate the severity of oil stains，and residues from metal pretreatment may also indirectly induce oil stains by damaging the integrity of the oil film.Based on the mechanism analysis，comprehensive methods including optimizing the selection of rust inhibitors，reducing the content of unsaturated components，introducing antioxidants and controlling environmental humidity are proposed to effectively reduce the oil stain risk during the application of rust-preventive oils.

To reveal the corrosion behavior and mechanisms of casing and tubing steels in CO2 and H2S synergistic environments under hightemperature and high-pressure conditions，dynamic corrosion simulation experiments were conducted on five commercial casing and tubing steels (N80-1 steel，L80-1 steel，L80-13Cr steel，P110SS steel，P110 steel) under extreme CO2 and H2S conditions (450 ℃，21.00 MPa)using a high-temperature and high-pressure autoclave.Combined with weight loss measurements and X-ray diffraction (XRD) characterization，the dominant corrosion mechanisms，phase transformation laws of corrosion products，and the influence of temperature alternation on the stability and cracking behavior of corrosion product films were explored.The results showed that: (1) In the high-temperature and high-pressure CO2-H2O system examined in this study，FeO was identified as the primary corrosion product phase of all five casing and tubing steels，the their corrosion resistance ranked in descending order as follows: P110 steel＞L80-13Cr steel＞P110SS steel＞L80-1 steel＞N80-1 steel.The corrosion rate was significantly increased by 77%－371%with increasing water vapor partial pressure，which was attributed to the enhanced ion activity in near-critical water and the reduced stability of corrosion product films.(2) Under the high-temperature and high-pressure CO2/H2S coexisting environment (CO2 partial pressure of 2.43 MPa；H2S partial pressure of 1.21 MPa)，corrosion was dominated by H2S，and Fe7S8 was formed as the main corrosion product.The corrosion resistance of the five casing and tubing steels to CO2-H2S-H2O was positively correlated with the Cr content in the steels，and the order from best to worst was L80-13Cr steel＞P110SS steel＞N80-1 steel＞L80-1 steel＞P110 steel.Notably，temperature cycling (from 450 ℃ to ambient temperature) was prone to triggering a “film rupture-hydrogen permeation-stress concentration” cascade effect，which markedly increased susceptibility to sulfide stress corrosion cracking and doubled the corrosion rate (e.g.，P110 steel: from 8.11 mm/a to 16.77 mm/a).(3)With a high Cr content (12.331%)，L80-13Cr steel effectively optimized the corrosion product film structure and suppressed hydrogen permeation，and exhibited superior corrosion resistance in both extreme environments；thus，it was identified as the preferred material for deep thermal recovery wellbore pipes.This study provided an important basis for the scientific selection and corrosion protection design of casing and tubing materials under extreme working conditions.

In practical applications of regional cathodic protection (CP) technology，problems such as excessive CP current demand and cathodic shielding often occur.To address the limitations of evaluating the regional CP system effectiveness at a specific station solely based on 20 detection points，this study integrated field detection and numerical simulation techniques to systematically analyze the CP effectiveness and potential distribution characteristics of pipelines in the station area，proposed pipeline corrosion monitoring and CP system optimization schemes，and revealed the action mechanism of cathodic shielding in regional CP systems.The results showed that:(1) Among the four types of CP optimization schemes，the protection effect of applying impressed current to under-protected hot-spot pipeline sections was the most optimal；(2)Without a grounding system，the shielding effect of parallel pipelines with the same diameter was weak (potential difference ＜5 mV)；(3)When large-diameter and small-diameter pipelines were laid in parallel，large-diameter pipelines exerted cathodic shielding on small-diameter pipelines，leading to a potential difference of 38 mV；(4) When grounding bodies were adjacent to pipelines，the cathodic shielding effect was enhanced；when grounding bodies crossed pipelines，the shielding range expanded to 24 m，and the pipeline potential shifted positively by 400 mV.This research provided a theoretical basis and practical guidance for the design，operation，and maintenance of station-area cathodic protection systems.

At present，cyanide-based electroless gold plating remains the dominant process in printed circuit board (PCB) manufacturing.Because cyanides are highly toxic and pose severe environmental risks，they are unfavorable for green and economically sustainable production；therefore，cyanide-free gold-plating systems have attracted increasing attention.Among cyanide-free gold plating systems，sulfite-based electroless gold plating has been extensively studied and widely used.However，the poor bath stability and the tendency to form coarse gold grains in sulfite-based systems have constrained further development and application.In this study，2-hydroxypyridine was introduced as an auxiliary coordination agent into a sodium gold sulfite plating system，and its effects on plating rate，bath stability，deposit properties，and the plating process were investigated.To examine how 2-hydroxypyridine influences the plating system and plating performance，electroless gold plating experiments were carried out on copper-clad laminates using baths containing different concentrations of 2-hydroxypyridine (0，2，5，8，10 g/L).The plating rate over 0－60 min was calculated to analyze the effect of 2-hydroxypyridine concentration on the gold deposition rate.The surface morphology of the gold deposits obtained at different concentrations was characterized by scanning electron microscopy (SEM).The effects of 2-hydroxypyridine concentration on coating performance were investigated using Tafel polarization curves measured with an electrochemical workstation，energy-dispersive spectroscopy (EDS) for elemental analysis，and solderability tests.Linear sweep voltammetry was employed to analyze the influence of 2-hydroxypyridine on the gold reduction process.In addition，the coordination mechanism between Au＋and 2-hydroxypyridine was discussed to elucidate changes in bath stability after introducing the auxiliary coordination agent.The results showed that 2-hydroxypyridine provided an auxiliary complexation effect in the sodium gold sulfite system.When the concentration of 2-hydroxypyridine was 5 g/L，the plating rate was 0.208 μm per 10 min during 0－10 min and 0.170 μm per 10 min during 50－60 min.Analysis of the surface microstructure of the gold deposits and the cross-sectional microstructure after soldering indicated that adding 2-hydroxypyridine reduced nickel corrosion during plating and improved the solderability of the gold deposits.When the 2-hydroxypyridine concentration was 5－8 g/L，the deposits exhibited better corrosion resistance and more pronounced cathodic polarization behavior.Mechanistically，the pyridine N atom and the Ogroup acted as dual electron donors that matched well with Au＋as a soft acid；moreover，d-electron back-donation from Au＋to the pyridine π* orbital strengthened the bonding and enhanced complex stability.This study provided a reference for the further application of cyanide-free electroless gold plating in PCB surface treatment technologies.

The importance of reliable and stable operation of equipment and materials，which directly serves equipment development and combat effectiveness generation，cannot be ignored.Firearms are among the most basic and widely used weapons，and their importance is self-evident given their high frequency of use and broad deployment.Numerous examples show that improper storage，inadequate protective maintenance，and limited corrosion-protection measures can lead to rusting or damage of firearms.However，existing research largely focuses on verifying whether the corrosion resistance of materials meets specifications，lacking a systematic analysis of the corrosion behavior and mechanisms of gun barrel materials in simulated marine atmospheric environments.Therefore，this study aimed to investigate the corrosion behavior and intrinsic mechanisms of a specific gun barrel material in a marine atmospheric environment by integrating multiple experimental methods，thereby providing theoretical support for developing targeted corrosion-mitigation technologies for such materials.To achieve the research objectives，a combination of experimental methods was employed.First，salt spray tests (compliant with the GB/T 10125－2021 standard，using 5%NaCl solution，pH 6.5－7.2) were conducted to simulate the marine atmospheric environment and accelerate the corrosion process.Second，corrosion electrochemical analysis was performed using a custom-made double-comb planar electrode (with an electrode spacing of 100 μm and a working area of 1 cm2)，and electrochemical impedance spectroscopy (frequency range:10－2－105 Hz) was measured to analyze the electrochemical reaction resistance.Third，the weight loss method was utilized: an electronic balance (0.1 mg precision) was used to weigh the gun barrel material specimens (dimensions:φ10 mm×2 mm) before and after corrosion to calculate the average corrosion rate.Fourth，Fourier Transform Infrared Spectroscopy (FT-IR，resolution 4 cm－1，scanning range 4 000－400 cm－1) was utilized to identify the types of corrosion products.Finally，the cross-sectional microstructure of the corrosion product layer was observed via Scanning Electron Microscopy (SEM，accelerating voltage 15 kV).The salt spray test results indicated that during the short-term corrosion process (7 d)，the corrosion rate of the gun barrel material remained essentially stable，with no significant acceleration or inhibition.The average corrosion rate was approximately 1.40 mm/a，and the generated corrosion products were loose and porous，providing limited protective effects to the substrate.FT-IR analysis confirmed that the primary corrosion products were γ-FeOOH，β-FeOOH，and δ-FeOOH.Electrochemical test results from the custom double-comb planar electrode showed that as the temperature increased (from 30 ℃ to 80 ℃)，the low-frequency impedance of the electrode decreased from 108 Ω·cm2 to 105 Ω·cm2，indicating a gradual increase in the corrosion rate.When the relative humidity (RH) increased from 50%to 70%，the low-frequency impedance significantly decreased (from 109 Ω·cm2 to 107 Ω·cm2)，corresponding to a higher corrosion rate.When the RH further increased from 70%to 90%，the Bode plots of the specimens at 90%RH exhibited two time constants，and the low-frequency impedance remained basically consistent with that at 80%RH (maintained around 107 Ω·cm2).This phenomenon was attributed to the formation of a continuous corrosion product film on the electrode surface at this humidity，which provided a certain degree of physical isolation.FT-IR analysis also revealed the evolution law of corrosion products: in the early stage of corrosion (within 1 d)，the surface corrosion products were mainly composed of γ-FeOOH and β-FeOOH.As the corrosion time extended from 2 d to 7 d，the intensity of the characteristic stretching vibration peaks of γ-FeOOH and β-FeOOH gradually increased，indicating the continuous accumulation of corrosion products.Meanwhile，δ-FeOOH gradually appeared in the corrosion products，and its content increased slightly with the extension of corrosion time.SEM observations further confirmed that the corrosion product layer was loose and contained numerous micro-cracks，which failed to effectively prevent the penetration of corrosive media (such as Cl－) into the substrate.This study systematically revealed the corrosion behavior and mechanisms of the gun barrel material in a simulated marine atmospheric environment.The results confirmed that temperature and relative humidity were key factors affecting the corrosion of the material: the corrosion tendency increased with rising temperature，and the charge transfer resistance (Rct)decreased (from 109 Ω·cm2 to 107 Ω·cm2) as the relative humidity increased (RH ＝50%－90%)，thereby leading to an increased corrosion rate.During the short-term corrosion process，the average corrosion rate of the material was stably maintained at approximately 1.40 mm/a，and the generated corrosion products (γ-FeOOH，β-FeOOH，δ-FeOOH) were loose and porous，offering limited protection to the substrate.These findings clarified the corrosion laws of the gun barrel material in a marine atmospheric environment and laid a foundation for the subsequent development of targeted anti-corrosion measures (such as surface coating modification).

This study aimed to evaluate the long-term service performance of Q345R steel in a high-temperature nitrate molten salt environment，thereby providing corrosion data and a theoretical basis for its application in emerging high-temperature fields such as molten-salt thermal energy storage and nuclear energy.Driven by the “dual-carbon” goals and the rapid development of renewable energy technologies，more stringent requirements are imposed on the high-temperature corrosion resistance of materials.Although Q345R steel is cost-effective and widely used，the long-term corrosion mechanism of Q345R steel in nitrate molten salts，particularly the dynamic evolution and failure mechanisms of the oxide film，remained unclear.Accordingly，the corrosion behavior of Q345R steel in nitrate molten salt (40%KNO3＋60%NaNO3，mass fraction) at 400 ℃ for up to 1 200 h was systematically investigated.Corrosion kinetics were obtained using the weight-loss method，and the oxide film formation process and protective mechanism were elucidated by combining optical microscopy (OM)，X-ray diffraction (XRD)，scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS)，and first-principles density functional theory (DFT) calculations.Results showed that as the exposure time increased from 300 h to 1 200 h，the mass loss increased from 0.003 3 g/cm2 to 0.008 5 g/cm2，whereas the corrosion rate exhibited a decreasing trend，dropping from 1.097 2×10－5 g/(cm2·h) within the initial 300 h to 6.392×10－6 g/(cm2·h) at 1 200 h.XRD analysis confirmed that the corrosion product on the surface was Fe3 O4，whose diffraction intensity increased with corrosion time，while the diffraction signal from the Fe substrate weakened，indicating continuous formation and progressive surface coverage of the Fe3O4 oxide film.SEM observations revealed that the corrosion morphology evolved from uniform pitting in the early stage to an “island-like” morphology caused by localized spallation of the oxide film.Cross-sectional analysis indicated that the Fe3O4 film thickness increased from 11.43 μm at 300 h to 22.50 μm at 1 200 h，accompanied by gradual densification of the film.Although minor localized delamination was observed at later stages，the film remained well bonded to the substrate overall.EDS results showed that the oxygen content increased markedly with exposure time and reached 28.14%(mass fraction) at 600 h，further confirming the progression of surface oxidation.DFT calculations demonstrated，at the atomic scale，that a charge transfer of 0.48 e occurred across the Fe/Fe3O4 interface，which enhanced interfacial chemical bonding and thereby enhancing the adhesion and protective performance of the oxide film.In conclusion，the gradual formation and densification of the Fe3O4 oxide film were identified as the key factors responsible for the decreased corrosion rate.This work clarified the corrosion evolution of Q345R steel in nitrate molten salts and provided an important reference for the lifetime prediction and formulation of corrosion protection strategies for Q345R steel in high-temperature service environments.

In order to improve the surface condition of collector rings in hydrogenerators and to enhance the current-carrying characteristics and operational stability of the brush/ring tribo-pair，Al and NiCr coatings were deposited on the surface of 45 steel，a commonly used collectorring material，via supersonic plasma spraying technology.The arc-erosion resistance of the two coatings was evaluated using a self-developed current-carrying wear test rig，and the friction coefficient，contact resistance，and temperature-rise behavior of the Al and NiCr coatings were analyzed at different current densities (0－12 A/cm2).Results showed that both coatings exhibited good resistance to arc erosion，with the NiCr coating exhibiting superior arc-erosion resistance.After 10 s of arc erosion，the Fe content on the NiCr-coated surface was only 2.72%，whereas that on the Al-coated surface was 3.65%.Owing to its low hardness and the continuous Al2O3 oxide film formed on its surface，the Al coating exhibited a lower friction coefficient: the friction coefficient was 0.494 under the no-current condition and increased to 0.541 at a current density of 12 A/cm2.However，its contact resistance remained relatively high.In contrast，an oxide film with semiconducting properties formed on the surface of the NiCr coating，resulting in a lower contact resistance；at a current density of 12 A/cm2，the contact resistance of the NiCr coating was 0.792 Ω.At low current densities，the Al coating exhibited the smallest temperature rise due to its high thermal conductivity.At medium to high current densities，the NiCr coating exhibited more stable temperature rise，as it generated less heat.These findings provided guidance for selecting coatings for hydrogenerator collector rings，indicating that coating selection should comprehensively consider current intensity and service conditions to optimize the long-term reliability of current-carrying tribo-pairs.

Phosphate coatings are widely applied to protect compressor blades in aero-engines.After spray deposition，these coatings are typically subjected to high-temperature thermal curing or vibratory finishing.However，limited research has been conducted to date on how these treatment methods affect the coating’s microstructure and corrosion resistance.In this study，an organophosphate coating was selected as the research object and subjected to three post-treatment processes:curing at 560 ℃(the original factory process，denoted as Process A)，curing at 350 ℃(the process adopted in this work，denoted as Process B)，and curing at 350 ℃ followed by vibratory finishing (adopted in this work，denoted as Process C).The performance of the three coatings was tested and evaluated using scanning electron microscopy (SEM)，a six-anda-half-digit multimeter，and an acidic salt spray chamber，among other methods.The results showed that the coatings exhibited distinctly different surface colors after the three post-treatments.Marked differences in surface morphology were also observed:the Process A coating surface was characterized by dense lamellar coverage，and the coating internal compactness reached approximately 87%；the Process B coating surface appeared as a loose granular structure with more internal pores，with a coating internal compactness of approximately 80%.Compared with the Process B coating，the surface morphology of the Process C coating changed dramatically，whereas its internal structure was almost unchanged.Results from the acidic salt spray test，resistivity measurements，and electrochemical polarization curve tests consistently indicated that the corrosion resistance of the coating subjected only to 560 ℃ curing (Process A) was moderate，while the coating cured at 350 ℃(Process B) exhibited the best corrosion resistance.In contrast，the coating cured at 350 ℃ followed by vibratory finishing (Process C) showed the poorest corrosion resistance，demonstrating that vibratory finishing severely deteriorated the corrosion resistance of the coating.This work provided reference data for selecting post-treatment schemes for coatings in engine manufacturing and was of great significance and practical value for balancing the comprehensive performance of such coatings.

Zinc is a biocompatible and biodegradable metallic material that is used in orthopedic repair and oral fixation applications.Because the mechanical properties of pure Zn are lower than the requirements for biomedical implants，the addition of alloying elements (e.g.，Mg，Li，Fe，Cu，and Al) can effectively improve the strength and toughness of Zn alloys.In particular，copper (Cu) not only provides antibacterial activity but also markedly enhances the mechanical strength of Zn-Cu alloys.Previous studies have extensively examined how deformation processes such as casting，drawing，and hot rolling affect the corrosion resistance of bulk Zn-Cu alloys；however，studies on the fabrication of Zn-Cu alloy coatings and their corrosion performance remain limited.Among various coating preparation technologies，cold spraying is a low-temperature and environmentally friendly process.During cold spraying，metal particles undergo plastic deformation upon high-velocity impact with the substrate and the already-deposited coating，and dense coatings are formed via successive particle accumulation.In this study，cold-sprayed Zn-Cu alloy coatings were prepared using stainless steel shots and Zn-6Cu particles as feedstock powders，and the effects of shot addition on the phase composition，microstructure，microhardness，and corrosion resistance of Zn-6Cu coatings were investigated.Zn-6Cu alloy coatings were fabricated via cold spraying using 1Cr18 stainless steel shot particles and Zn-6Cu alloy powder，with shot volume fractions of 0，30%，50%，and 70%.The phase composition of the cold-sprayed Zn-6Cu coatings was characterized by X-ray diffraction (XRD).The results showed that the coatings were mainly composed of the Zn phase and the CuZn5 phase，with a small amount of ZnO.During high-velocity continuous impacts between the shot particles and Zn-6Cu particles，significant internal stresses were induced within the coatings，which promoted an increased dislocation density and/or grain refinement of the Zn-6Cu particles.The full width at half maximum (FWHM) of the Zn(101) diffraction peak was measured as (0.062±0.002) rad，(0.110±0.002) rad，(0.116±0.003) rad，and (0.128±0.003) rad for coatings with 0，30%，50%，and 70%shot addition，respectively.The microstructure and the deposition morphology of individual particles were examined by scanning electron microscopy (SEM).The coating surfaces were found to exhibit a rough morphology and impact pits formed by shot collision and rebound，and the pit size increased with increasing shot content.Good interfacial bonding between the Zn-6Cu coating and the substrate was observed，and neither interfacial delamination nor internal cracking was detected.Except for a small number of tiny pores，dense interparticle bonding was achieved within the coatings.A mechanical mixing phenomenon was observed near the coating/substrate interface，particularly at shot volume fractions of 50%and 70%.From the deposition morphology of individual particles，some Zn-6Cu particles were shown to have been embedded into the polished substrate，whereas others rebounded after impact and produced pits on the substrate surface.Microhardness was measured on polished cross-sections using a Vickers microhardness tester.The microhardness values of the Zn-6Cu coatings were determined to be (82.7±4.1) MPa，(95.2±4.9) MPa，(104.3±8.5) MPa，and (108.9±24.3) MPa for shot additions of 0，30%，50%，and 70%，respectively.The corrosion performance of the Zn-6Cu coatings as a function of shot content was evaluated by linear sweep voltammetry and electrochemical impedance spectroscopy.Both the corrosion current density and the corrosion rate were found to decrease first and then increase with increasing shot content.Specifically，the corrosion current density was measured as (5.54±0.34)×10－5 A/cm2，(3.37±0.56)×10－5 A/cm2，(2.17±0.65)×10－5 A/cm2，and (2.93±0.73)×10－5 A/cm2，and the corrosion rate was calculated as (3.19±0.41) mm/a，(1.94±0.34) mm/a，(1.25±0.95) mm/a，and (1.69±0.89) mm/a for shot additions of 0，30%，50%，and 70%，respectively.With increasing shot addition from 30%to 70%，the charge-transfer resistance at the substrate/electrolyte interface (R1) was observed to decrease first and then increase，whereas the charge-transfer resistance at the coating/electrolyte interface (R2) was observed to increase first and then decrease；in all cases，both R1 and R2 were higher than those of the coating prepared without shot addition.Overall，the cold-sprayed Zn-Cu alloy coatings were mainly composed of Zn and CuZn5 phases with a small amount of ZnO.With increasing shot addition，the FWHM of the Zn(101) diffraction peak increased.The Zn-6Cu coatings exhibited rough surfaces and dense interiors，and the deposition of Zn-6Cu coatings was promoted by adding an appropriate amount of shots.Owing to the work-hardening effect，the microhardness of the Zn-6Cu coatings increased with increasing shot addition.The corrosion resistance of the Zn-6Cu coatings was improved when an appropriate amount of shots was introduced during cold spraying，and the best corrosion performance was achieved at a shot addition of 50%.

Electrodes are key components of vanadium redox flow batteries (VRFB)，and electrode properties largely govern the conversion efficiency between electrical and chemical energy.However，commercial graphite felt (GF) electrodes are dominated by inert sp2 carbon structures，leading to poor wettability，insufficient active sites，and slow charge-transfer kinetics，which severely constrain the VO2＋/VO2＋half-cell reaction.Although plasma treatments can introduce oxygen- and nitrogen-containing functional groups within short durations，substantial variations in plasma atmosphere，treatment time，and substrate pretreatment have limited comparability among reported results.Therefore，this study adopted a unified high-temperature activation baseline at 1 800 ℃ and systematically constructed a two-dimensional parameter window of plasma atmosphere，namely Ar，O2，and N2，together with treatment time，to develop a rapid and reproducible surface-engineering strategy for GF electrodes.Commercial carbon felt (CF) was first activated at 1 800 ℃ for 1 h under an inert atmosphere to obtain GF，while pristine CF was retained as a reference.Subsequently，GF was treated by Ar plasma for 1，3，5 min，by O2 plasma for 20，30，40 s，and by N2 plasma for 8，10，12 min，respectively.Fiber morphology and near-surface elemental composition were examined by scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDX).Wettability was evaluated by water contact angle measurements.Surface defects and graphitization were analyzed by Raman spectroscopy，and surface oxygen-containing functional groups and nitrogen configurations were identified by X-ray photoelectron spectroscopy (XPS).Electrochemical behaviors in the VO2＋/VO2＋half-cell were investigated in 3 mol/L H2SO4＋0.1 mol/L VOSO4 using cyclic voltammetry (CV)，electrochemical impedance spectroscopy (EIS)，and distribution of relaxation times(DRT) analysis to resolve charge-transfer and mass-transport contributions.Cycling stability was evaluated by 200 consecutive CV cycles at 25 mV/s.High-temperature activation increased the graphitization degree of GF.However，both CF and GF remained hydrophobic.After Ar，O2，and N2 plasma treatments，water droplets spread instantaneously and completely on the felt surface，indicating a transition from hydrophobic to fully wetting behavior.SEM-EDX and XPS results indicated that O2 plasma treatment for 30 s enriches polar oxygen-containing functional groups，including hydroxyl，carbonyl，and carboxyl species，on the fiber surface，while exerting a limited influence on the structural order of the carbon framework.In the VO2＋/VO2＋half-cell，the corresponding electrode exhibited the highest anodic/cathodic peak current densities and the lowest charge-transfer resistance (Rct).In DRT spectra，the high-frequency relaxation peak associated with charge transfer was markedly weakened，consistent with accelerated interfacial reaction kinetics.For N2 plasma treatment for 10 min，XPS test results confirmed the coexistence of pyridinic-N，pyrrolic-N，graphitic-N species，and high-binding-energy nitrogen species.A moderate increase in defect density was achieved while maintaining a relatively continuous sp2 framework，and the improvement was reflected by increased peak current densities and decreased Rct.In contrast，Ar plasma treatment for 3 min mainly introduced moderate surface defects via physical bombardment.As a result，peak current densities increased and Rct decreased relative to pristine GF，whereas the enhancement remained weaker than that obtained from the O2 and N2 systems.Regarding cycling stability，the optimal plasma-treated electrodes Ar＿GF (TAr ＝3 min)，O2＿GF (TO2 ＝30 s)，and N2＿GF (TN2 ＝10 min) exhibited cathodic peak current decay rates of 16.7%，13.9%，and 13.4%，respectively，after 200 cycles，whereas the corresponding anodic peak current density decay rates were smaller，at 5.9%，0.2%，and 1.0%，respectively.Meanwhile，the peak-topeak separation (ΔEp) increased by 0.10～0.13 V，corresponding to a relative increase of approximately 14.7%～18.8%.After 200 cycles，the CV profiles still display relatively symmetric anodic and cathodic peaks，indicating that interfacial kinetics showed measurable attenuation within the investigated cycling range，whereas the overall electrochemical response remained stable，without evidence of pronounced deactivation or severe interfacial passivation.Under a unified 1 800 ℃ high-temperature activation baseline，Ar，O2，and N2 plasma treatments effectively improved VO2＋/VO2＋half-cell interfacial kinetics on GF electrodes by regulating surface defects，polar oxygen-containing functional groups，and nitrogen-doping configurations.Among the investigated conditions，O2 plasma treatment for 30 s yielded the fastest interfacial reaction kinetics，whereas N2 plasma treatment for 10 min provided a more balanced optimization between electrochemical activity and structural integrity.The two-dimensional window of atomosphere and treatment time provided targeted guidance for plasma-based surface engineering of GF electrodes and offer a practical basis for positive electrode optimization in VRFBs.

Mechanical seals are key components for preventing fluid leakage in industrial equipment.With the rapid development of industrial automation and high-end manufacturing，their actual operating conditions are becoming increasingly severe.Surface texturing technology has important application value for improving the comprehensive performance of mechanical seals under complex operating conditions.Based on previous multi-objective optimization results，surface texture arrays with different profiles (horseshoe-shaped，kidney-shaped，circular，and elliptical) were prepared on the end face of the moving ring of mechanical seals.A high-speed sealing friction tester was employed to investigate the comprehensive effects of texture shape on the friction performance and leakage characteristics of mechanical seals.The experimental results showed that under the low load range (50－70 N) and high-speed operating conditions (4 000－4 800 r/min)，the circular texture exhibits excellent comprehensive performance with low friction and low leakage，owing to the uniform hydrodynamic pressure distribution formed by its symmetrical geometric features.Under the high load range (70－110 N) and medium-high rotational speed range (800－4 800 r/min) operating conditions，the kidney-shaped texture showed better comprehensive performance in the experiment，owing to the continuous hydrodynamic lubrication effect generated by its double-curvature edge structure.The research results revealed the intrinsic correlation between texture morphology and the comprehensive performance of mechanical seals，and provide a theoretical basis for the surface texture design on high-performance mechanical seals.

With global warming driving the accelerated melting of polar glaciers，regular navigation in the Arctic and Antarctic regions has become increasingly feasible.Polar shipping routes hold significant strategic significance in enriching maritime trade routes and reducing reliance on traditional shipping lanes.However，the harsh extreme low-temperature environment in polar regions poses severe challenges to the friction and wear properties of marine steels，directly affecting navigation safety and maintenance costs.Existing studies on the low-temperature wear properties of marine steels lack systematic comparisons between novel F-grade low-temperature steels fabricated via Thermomechanical Control Processing (TMCP) and traditional structural steels under extreme polar temperatures.To fill this gap，this study aimed to investigate the friction and wear behaviors and intrinsic mechanisms of F40 low-temperature steel and normalized-rolled Q355 high-strength low-alloy steel within the temperature range of－60 ℃ to room temperature，thereby providing a scientific basis for material selection in polar shipbuilding.The experimental materials were F40 steel and Q355 steel.The chemical composition (mass fraction) of F40 steel was as follows: C 0.060%，Si 0.300%，Mn 1.500%，Ni 0.800%，Cr 0.200%，V 0.100%，Nb 0.050%.The chemical composition (mass fraction) of Q355 steel was: C 0.140%，Si 0.350%，Mn 1.000%，Ni 0.500%，Cr 0.300%，V 0.100%，Nb 0.050%.Metallographic analysis results showed that F40 steel exhibited significantly refined grains (average diameter of 45.4 μm) with a lath ferrite structure，while Q355 steel had a coarser pearlite-ferrite structure (average grain diameter of 125.1 μm).The base hardness values of F40 steel and Q355 steel were 202 and 169 HV，respectively.Friction and wear tests were conducted using a UMT-3 Tribolab tester，with an 8 mm-diameter alumina ceramic ball as the counterbody.The test parameters were set as follows: normal load of 30 N，reciprocating frequency of 2 Hz，sliding distance of 10 mm，and test duration of 30 min.A temperature gradient ranging from 20 to－60 ℃(20，0，－20，－40，－60 ℃) was achieved using a thermocouple temperature control system.The tribological properties of the two steels were characterized by friction coefficient curves and wear rates；wear scar morphology and microstructures were analyzed using a Bruker Contour GT-I white light interferometer，a Zeiss Gemini SEM 300 scanning electron microscope(SEM)，and an energy dispersive spectrometer (EDS).The test results indicated that temperature exerted a significant regulatory effect on the tribological properties of both steels.The average friction coefficient of Q355 steel increased linearly from 0.351 at 20 ℃ to 0.681 at－60 ℃，representing an increase of 94%；the average friction coefficient of F40 steel increased from 0.346 at 20 ℃ to 0.651 at－60 ℃，representing a relatively moderate increase of 88%.The wear rates of both steels showed a non-linear trend of “initial increase，subsequent decrease，and final re-increase”: at room temperature，the wear rates of F40 steel and Q355 steel were 0.029×10－3 mm3/(N·m) and 0.044×10－3 mm3/(N·m)，respectively；both reached their peak values at－20 ℃，which were 0.384×10－3 mm3/(N·m) and 0.622×10－3 mm3/(N·m)，increasing by 12.2 times and 13.1 times compared to room temperature，respectively.At－40 ℃，a flat adhesive layer formed on the wear scar surface，covering the spallation pits and reducing the effective contact stress，resulting in a slight decrease in wear rate.At－60 ℃，cryogenic hardening exacerbated the brittle fracture of the material，leading to a rebound in wear rate.At this temperature，the microhardness at the central region of the wear scar cross-section of F40 steel and Q355 steel reached 352.5 HV and 320.3 HV，respectively.Observations using white light interferometer showed that the wear scar depth of both steels reached the maximum at－20 ℃，with 39.3 μm for F40 steel and 111.5 μm for Q355 steel，confirming that F40 steel has superior wear resistance.SEM and EDS analyses indicated that the wear mechanism evolved with decreasing temperature:adhesive wear dominated at 20 ℃，while it transformed into a composite form of abrasive wear and fatigue wear in low-temperature environments.Q355 steel experienced severe detachment of lamellar cementite，forming numerous wear pits and grooves；in contrast，F40 steel inhibited dislocation slip，stabilized the oxide film，and reduced adhesive damage by virtue of its refined grain structure，thereby forming smaller wear scars and exhibiting a lower friction coefficient.This study systematically clarified the temperature-dependent friction and wear behaviors of F40 steel and Q355 steel in polar environments.F40 steel fabricated via the TMCP process exhibits better wear resistance than Q355 steel under low-temperature conditions，owing to its refined grain structure and enhanced work hardening effect.The non-linear variation of wear rate and the transition of wear mechanism highlight the critical role of the synergy between cryogenic effects and fine-grain strengthening in improving material performance under extreme conditions.The research results provide valuable references for the selection and optimization of marine steels for polar ships，and are of great significance for ensuring the safe and efficient operation of marine equipment in extreme low-temperature environments.

Power transmission and transformation equipment of power grids is exposed to complex atmospheric environments during long-term service，and its corrosion exhibits significant spatial heterogeneity.Conventional field exposure tests are limited by the number of sampling sites，making it difficult to accurately reflect the overall corrosion characteristics at the provincial scale，thus leading to a lack of intuitive basis for material selection in regional corrosion protection.Based on the province-wide field test data in Henan Province，this study focused on analyzing the spatial distribution of corrosion of Q235 carbon steel and galvanized steel as well as their main driving factors，and explored the spatial distribution characteristics of atmospheric environmental factors to provide support for material selection，protection zoning，and operation and maintenance (O＆M) decision-making of power grid equipment.Based on three-year field exposure test data of metal samples from 133 substations and data from 113 atmospheric environmental monitoring stations，the ordinary kriging (OK) interpolation method was employed to generate spatial distribution maps of the atmospheric corrosion of the samples and atmospheric environmental factors，respectively.Four semivariogram models，namely triangular，spherical，exponential，and Gaussian models，were compared，and the optimal interpolation model was selected via cross-validation.Finally，grey relational analysis (GRA) was adopted to quantify the influence of atmospheric environmental factors on corrosion rates，so as to clarify the main environmental driving factors for the corrosion of the two materials.The research results showed that: (1) The atmospheric environment in Henan Province exhibited significant spatial heterogeneity.The concentrations of pollutants (such as PM2.5 and SO2) exhibited a distribution pattern of “higher in the north and lower in the south”，while temperature and humidity exhibited a characteristic of “higher in the south and lower in the north”；(2) The high-corrosion regions for carbon steel and galvanized steel were completely different.The high-corrosion areas of carbon steel were concentrated in the industrially developed central and western industrial zones such as Luoyang and Pingdingshan，while those of galvanized steel were located in southeastern regions such as Shangqiu and Zhumadian；(3)Cross-validation showed that the exponential model was most suitable for carbon steel corrosion prediction (mean error (ME) was 0.003 18 μm/a，mean relative error (MRE) was 16.86%)，while the triangular model exhibited the best performance in galvanized steel corrosion prediction (ME was－0.000 32 μm/a，MRE was 22.29%)；(4) There were essential differences in the main atmospheric environmental factors driving the corrosion behavior of carbon steel and galvanized steel.The GRA results showed that relative humidity (Hum) and temperature(Temp) were the primary factors driving the corrosion of both materials.For carbon steel，the grey relational grade ranking was Hum(0.713 3)＞Temp(0.678 1)＞PM2.5 (0.677 3)＞PM10(0.677 2)＞SO2(0.657 0)，indicating that its corrosion was mainly driven by the synergistic effect of hygroscopic particulate matter under high-humidity conditions；for galvanized steel，the ranking was Hum (0.699 8)＞Temp(0.689 1)＞SO2(0.666 9)＞NO2(0.653 2)，indicating that its corrosion was more sensitive to humidity and acidic gases.This study integrated the application of geostatistical interpolation and grey relational analysis methods to construct，for the first time，atmospheric corrosion maps of metallic materials used in power grids in Henan Province，filling the gap in regional corrosion assessment of power grid materials in Henan Province.Cross-validation results showed that the exponential model and triangular model were suitable for predicting the corrosion rates of carbon steel and galvanized steel，respectively.GRA indicated that although both materials were dominated by humidity and temperature，carbon steel was more sensitive to particulate matter，while acidic gases had a more prominent impact on galvanized steel.The research results provided a scientific basis for differentiated corrosion protection strategies of power grid equipment in Henan Province and had important engineering value for extending material service life and ensuring the safe operation of power grids.

Copper alloys are widely used in the field of equipment manufacturing due to their excellent electrical conductivity，thermal conductivity，and processability.However，their inherent drawbacks of low hardness and poor wear resistance render them susceptible to failure in electrical contact applications.Ni-Mo alloy coatings，which exhibit a combination of high hardness，excellent corrosion resistance，and hightemperature stability，are an ideal solution for surface strengthening of copper alloys，and pulse electrodeposition parameters (duty cycle，current density，frequency) exert a crucial influence on the properties of Ni-Mo coatings.Traditional experimental optimization methods are costly and inefficient，and it is difficult to balance the competitive relationships among multiple performance indicators.Therefore，this study adopted response surface methodology (RSM) combined with genetic algorithm (GA) to perform multi-objective optimization of the pulse electrodeposition process of Ni-Mo coatings on H62 copper alloy surface，aiming to obtain the process parameter combination with optimal comprehensive performance.Taking duty cycle (10%－50%)，current density (2－4 A/dm2)，and frequency (100－500 Hz) as independent variables，and the microhardness，steady-state friction coefficient，wear rate，self-corrosion current density，and charge transfer resistance of the coating as response values，this study designed 15 experimental schemes based on the Box-Behnken design.The structure and properties of the coatings were systematically characterized using X-ray diffraction (XRD)，field emission scanning electron microscopy (FE-SEM)，a microhardness tester，a reciprocating friction and wear tester，and an electrochemical workstation.The results showed that a low duty cycle favored the formation of fine-grained structures，thereby significantly enhancing the coating hardness (up to 533 HV0.05).A significant trade-off relationship existed between the wear resistance and corrosion resistance of the coatings.Based on the response surface model，the contribution degree of each parameter was quantified: the contribution ratios of duty cycle to microhardness，steady-state friction coefficient，and wear rate were determined to be 66.21%，61.79%，and 84.46%，respectively；the contribution ratio of frequency to self-corrosion current density was 38.83%；and the contribution ratio of duty cycle to charge transfer resistance was 59.35%.The genetic algorithm (GA) was employed to obtain the Pareto optimal solution set，and the optimal process parameters were determined through weighted decision-making as follows: duty cycle 10%，current density 4 A/dm2，and frequency 460 Hz.The optimized coating formed a fine-grained and high-molybdenum composite structure with a molybdenum content of 16.69%，and its comprehensive performance was significantly improved: the microhardness was 471.287 HV0.05，the steady-state friction coefficient was reduced to 0.264，the wear rate was as low as 2.985 0×10－5 mm3/(N·m)，the self-corrosion current density was 1.734 0×10－6 A/cm2，and the charge transfer resistance was 7 748 Ω·cm2.In comparison with the optimal group from the response surface experiments (duty cycle 10%，current density 3 A/dm2，frequency 500 Hz)，the steady-state friction coefficient of the optimized group decreased by 4%，the wear rate decreased by 0.64%，and the self-corrosion current density decreased by 6.93%.With a minor reduction in hardness (3.48%)，both wear resistance and corrosion resistance were improved concurrently.The integration of RSM and GA effectively addressed the multi-parameter and multi-objective optimization challenge associated with the pulse electrodeposition process，quantified the mechanism underlying the influence of parameter interactions on coating properties，and provided a scientific basis and technical support for the process optimization of Ni-Mo coatings on copper alloy surfaces.It is of great significance for improving the surface performance of copper alloy materials and expanding their application scenarios.

Buried metal pipelines are the core infrastructure for energy transportation.Serving in complex underground environments for extended service periods，they are susceptible to multiple corrosion factors，which may pose safety and ecological risks.As the first line of defense against pipeline corrosion，external protective coatings still have insufficient applicability and performance limitations in practical engineering.Therefore，it is necessary to deeply analyze the occurrence and development mechanism of external corrosion of metal pipelines，clarify the performance characteristics and application conditions of mainstream protective coatings，and directionally optimize coating technologies according to actual engineering needs，so as to provide theoretical support and technical reference for the prevention and control of external corrosion of buried pipelines.The external corrosion of buried metal pipelines is mainly affected by a combination of corrosive environmental factors and external influencing factors.Soil is a complex electrolyte system，among which the soil pH value is the most critical factor，and the corrosion rate of pipeline steel increases significantly with decreasing pH value.The effect of soil moisture on corrosion shows a trend of increasing first and then decreasing；high temperature aggravates corrosion through multiple mechanisms such as accelerating electrochemical reactions and reducing the stability of corrosion products.Researchers have established the RS-EW-SPA composite model to achieve quantitative evaluation of soil corrosion.Microorganisms are the core driving factors of corrosion，accelerating corrosion through mechanisms including electron exchange，oxygen concentration cells induced by biofilms，and passive film destruction，among which sulfate-reducing bacteria (SRB) pose the most prominent hazard.Stray current is the most significant external corrosion factor and can be classified into DC(direct current) and AC(alternating current) types.DC stray current (including steady-state and dynamic type) induces anodic dissolution by forming electrochemical corrosion circuits，with steady-state DC interference exerting a particularly significant corrosive effect；AC stray current has a relatively weaker corrosion effect，but its long-term action will damage the passive film on the pipeline surface，posing a potential threat to the safe service of pipelines.In the field of external protective coatings for buried pipelines，coatings commonly used in engineering applications，including Fusion-Bonded Epoxy (FBE)，Dual Powder System (DPS)，Three-Layer Polyethylene (3PE)，and High-Performance Anti-Corrosion Coating (HPCC)，each have their optimal application scenarios.For instance，HPCC exhibits the optimal mechanical properties and temperature resistance performance，making it suitable for extreme environments；3PE possesses balanced comprehensive performance；DPS stands out with excellent adhesion and chemical corrosion resistance；while FBE has advantages in cost-effectiveness and constructability.In recent years，nanomaterialmodified coatings have emerged as an important research direction.By selecting appropriate nanofillers and precisely regulating their addition amounts，the protective performance of coatings can be directionally optimized.For example，nanosilica fills the pores of coatings to form a dense protective barrier，simultaneously enhancing salt penetration resistance and impact resistance.Such modification strategies are mostly application-demand-oriented，achieving breakthroughs in protective performance through the synergistic effect of different nanomaterials.The core conclusions can be summarized into three points: Firstly，the external corrosion of buried metal pipelines is a complex process characterized by the coupling of multiple factors，and its synergistic action mechanism needs to be analyzed from a systematic perspective.Secondly，traditional protective coatings need to be selected based on adaptation to engineering scenarios，while nanomaterial-modified coatings，through multi-mechanism synergistic effects，serve as an important direction for improving protection levels.Thirdly，current corrosion prediction models and coating technologies still have limitations，and it is necessary to promote technological upgrading from the dual dimensions of theoretical research and material innovation.Looking ahead，efforts should focus on two core dimensions for systematic advancement:On one hand，deepen the research into the multi-factor coupling corrosion mechanisms，optimize and improve corrosion prediction models，so as to provide theoretical support for the accurate prediction of pipeline corrosion risks and targeted prevention and control in complex environments.On the other hand，strengthen the innovation of protective coating technologies，promote the research，development and application of nanomaterial modification and intelligent nanofillers，and construct a long-term protective system suitable for complex underground environments.

In response to the environmental risks posed by traditional heavy metal-based sealing systems for anodic aluminum oxide films of aluminum alloys，it is imperative to systematically analyze the reaction mechanisms and corrosion resistance mechanisms of environmentally friendly sealing technologies.By reviewing the preparation process and porous structure characteristics of anodic aluminum oxide films on aluminum alloys，this paper analyzes the technical limitations of traditional sealing methods (hot water/chromium salts/nickel salts).Then，it focuses on three environmentally friendly systems of Li，Ce，and Mn，and carries out discussions from multiple dimensions such as sealing reaction pathways，product chemical properties，corrosion resistance mechanisms，and self-healing functions.The sealing behavior of the Li salt system is regulated by pH values，LiAlO2 and LiAl-LDH (layered double hydroxide) are formed under acidic conditions and alkaline conditions，respectively.Its corrosion resistance derives from the physical barrier effect and interlayer ion-exchange reactions.The Ce salt system exhibits excellent dynamic self-healing ability，which is attributed to the valence state transition between Ce3＋and Ce4＋，and its corrosion resistance mechanism relies on the synergistic effect of hydrolysis products in physical blocking and chemical passivation.The Mn salt system mimics the passivation mechanism of chromate by establishing a multivalent cycle among Mn2＋，Mn4＋，and Mn7＋.The redox reactions generated by this cycle can be re-triggered in the damaged areas of the material surface，thus driving the redeposition and re-passivation of active components.Based on the clarified structure-activity relationships and mechanism differences of the Li/Ce/Mn systems，this paper provided a theoretical framework for the design of chromium-free sealing technologies，and pointed out that improving environmental adaptability via valence state regulation and multi-mechanism coupling represents the core development direction for future research.

With the rapid development of hypersonic flight vehicles and advanced aerospace propulsion systems，key hot-end components such as nose cones，wing leading edges，and nozzle throat liners are subjected to long-term extremely coupled environments involving ultrahigh temperatures，severe oxidation，and high-velocity gas flow impingement during service.These conditions impose exceptionally stringent requirements on the oxidation and ablation resistance of protective materials.Ultrahigh-temperature ceramic (UHTC) coatings，featuring ultrahigh melting points，excellent chemical stability at elevated temperatures，and strong ablation resistance，are regarded as one of the most promising material systems for next-generation thermal protection.The research progress on oxidation-resistant and ablation-resistant UHTC coatings was systematically reviewed in this paper，and the fabrication processes，oxidation-resistant and ablation-resistant behavior，and underlying mechanisms of carbide-based and boride-based UHTC coatings were summarized and analyzed.For carbide-based UHTC coatings，the failure characteristics of coatings such as ZrC，HfC，and TaC under high-temperature oxidation and ablation environments were critically evaluated，and the key roles of second-phase incorporation，solid-solution strengthening，and gradient and multilayer structural designs in suppressing crack propagation，alleviating thermal stress mismatch，and stabilizing oxide product layers were reviewed.For boride-based UHTC coatings，the oxidation-resistant and ablation-resistant mechanisms of coatings such as ZrB2，HfB2，and TaB2 were systematically analyzed，and the self-healing behavior of B2O3 and borosilicate glass phases，the structural support provided by high-melting-point oxide skeletons，and their temperaturedependent protective characteristics were summarized.Meanwhile，fabrication processes for UHTC coatings，including atmospheric plasma spraying，chemical vapor deposition/infiltration，reactive melt infiltration，pack cementation，and precursor impregnation and sintering，were reviewed.The relationships among coating microstructure，interfacial bonding state，and in-service performance under different processing conditions were analyzed，and key bottlenecks currently encountered by UHTC coatings under high-enthalpy gas flows and long-duration service，such as oxide-layer volatilization，interfacial degradation，and brittle damage，were identified and summarized.Finally，future directions involving multicomponent and multiphase composite design，interface engineering and regulation，and intelligent materials design were outlined，and useful references were provided for the optimized design and engineering application of oxidation-resistant and ablation-resistant UHTC coating systems.

In response to the problem of corrosion-induced perforation of J55 tubing starting from the inner wall in an oil well during service，a systematic analysis of the cause of failure was carried out.Through macroscopic observation，chemical composition analysis，metallographic examination，microscopic morphology and energy-dispersive spectroscopy(EDS) analysis and mechanical property testing of the failed samples，and in combination with the field service conditions，the failure mechanism of the tubing was identified.Results showed that the perforation failure was mainly caused by CO2 corrosion under high-temperature and high-pressure conditions，and the presence of Cl－ in the well fluid further accelerated the corrosion process.The chemical composition and mechanical properties of the tubing body were found to meet the requirements of the relevant standards.Metallographic and scanning electron microscopy(SEM) analysis revealed that the failure site exhibited typical CO2-induced moss-like corrosion and pitting characteristics，and FeCO3 particles were detected in the corrosion products.EDS analysis showed that the inner wall of the corrosion pits was enriched with C，O，Cl，Si，Fe and other elements.Combined with the water-quality analysis of the well fluid，it was confirmed that high mineralization and elevated HCO3－ content were key factors that aggravated the corrosion.Further analysis indicated that the existing standards for J55，N80 and P110 grade steel tubing specify only the limits for P and S contents，while lacking metallographic and corrosion-performance requirements.Moreover，J55 tubing is mostly manufactured from 37Mn5(36Mn6) steel，which has no corresponding domestic standard in China，leading to inadequacies in standard applicability.To address these issues，it is recommended to select tubing products with superior CO2 corrosion resistance according to the special downhole corrosive environment and to periodically add high-efficiency corrosion inhibitors.Meanwhile，it is suggested that revisions of relevant standards include the designation of steel grades and detailed technical requirements such as metallographic and corrosion-performance specifications，so as to improve the service life and safety of tubing under complex working conditions.

Sealing is a core factor for the safe operation of high-pressure proton exchange membrane electrolysis cells(PEMECs).To investigate the corrosion behavior of sealing polymer materials，two experimental methods were established: an accelerated high-temperature evaluation(100 ℃ acidic environment with H2 or O2 for 100 h) and a long-term high-pressure evaluation(80 ℃ acidic environment with 6－7 MPa H2 or O2 for 1 000 h)，to evaluate the corrosion behavior of five sealing polymer materials.Results showed that ethylene-propylene-diene monomer(EPDM) and fluoroelastomer(FKM) had chemical degradation and localized corrosion.In contrast，polyimide(PI)，polyetheretherketone(PEEK) and polytetrafluoroethylene(PTFE) had low corrosion rates and showed uniform corrosion characteristics.Specifically，PTFE showed excellent corrosion resistance，and its composite structure may help address corrosion and assembly issues in high-pressure PEMEC systems.

To investigate the leakage failure of a welded joint in a preheater unit of a certain alumina plant，macroscopic inspection，chemical composition analysis，mechanical property testing，metallographic examination，scanning electron microscopy(SEM) and energy-dispersive spectroscopy(EDS) were conducted to identify the cause of cracking，and finite element analysis was performed to evaluate the stress state.Results showed that cracks initiated at multiple locations in the transition section near the flange welded joint of the preheater and propagated from the inner wall toward the outer wall.The fracture surface exhibited typical brittle intergranular fracture characteristics.The failure mode was identified as stress corrosion cracking induced by the combined effects of operating stress，welding residual stress and the alkaline Bayer liquor.The failure mechanism was attributed to anodic dissolution，and a corresponding anodic dissolution stress corrosion cracking model under the combined action of stress and alkaline environment was established.Finally，several countermeasures were proposed，including optimizing welding and heat treatment procedures and installing additional supports and hangers.This study provides valuable guidance for understanding stress corrosion cracking in alumina production units operating under the Bayer process.

 With the continuous advancement of staged fracturing technology，the application of high-strength dissolvable materials in downhole tools continues to expand.Such materials are able to dissolve automatically after fracturing operations，eliminating the need for drilling out and addressing issues associated with plug removal during staged fracturing.To investigate the dissolution behavior of dissolvable metallic materials and the factors influencing their dissolution rate，corrosion rate measurements，corrosion morphology observations and post-corrosion mechanical property tests were conducted on dissolvable aluminum-based alloys in different formation water solutions simulating downhole environments，under different exposure periods and temperatures.Morphological analysis at both the macro and micro scales showed that the corrosion rate of the dissolvable aluminum-based alloy in formation water B，which contains a higher concentration of Cl－，was greater than that in formation water A.After high-temperature and high-pressure autoclave testing in downhole formation water，the tensile strength and yield strength of the material decreased with increasing temperature and prolonged exposure time.This study provides a theoretical basis for whether dissolvable fracturing tools fabricated from dissolvable aluminum-based alloys can meet the performance requirements of downhole operating conditions.

To investigate the properties of multicomponent co-diffusion layers under mechanical energy assistance，multicomponent zinc alloy diffusion layers were prepared via a mechanically assisted diffusion process at different linear velocities.The surface morphology，thickness，elemental distribution，phase composition and hardness of the diffusion layers were characterized using scanning electron microscopy(SEM)，energy-dispersive spectroscopy(EDS)，X-ray diffraction(XRD) and microhardness testing.The corrosion resistance and wear resistance of the layers were evaluated using an electrochemical workstation and a multifunctional material surface tester.Results showed that the phases present in the diffusion layers included FeZn11，FeZn9，FeZn7，Al2O3 and MgZn2，and that the constituent elements were uniformly distributed across the layer surface.The diffusion layer thickness first increased and then decreased with increasing linear velocity，reaching a maximum of 87 μm at 25 mm/s.The hardness of the layers was only slightly affected by linear velocity and remained within the range of 400－420 HV0.1.When the linear velocity was 20 mm/s，the diffusion layer exhibited the best uniformity，compactness and overall corrosion resistance，corresponding to a self-corrosion potential of－0.569 1 V and a corrosion current density of 2.984×10-6 A/cm2.The friction coefficients of the diffusion layers were all approximately 0.35，with the lowest value of 0.32 obtained for the layer prepared at a linear velocity of 25 mm/s.

To investigate the effect of post-treatment methods for polyaniline microcapsules prepared by in-situ polymerization on the protective performance of coatings and to develop a protective coating for magnesium alloys with simple processing steps and good overall performance，three treatment approaches，including no treatment，washing，and washing followed by drying，were applied to the as-polymerized microcapsule emulsion.The treated emulsions were incorporated into an epoxy resin to prepare coatings.The mechanical properties and protective performance of the coatings were evaluated through pencil hardness，flexibility and electrochemical impedance measurements，and the results were compared with those of a pure epoxy varnish.Results showed that after microcapsule addition，the pencil hardness of the coating increased from H(for the epoxy varnish) to 2H，while its impact resistance and flexibility remained unchanged.The intact epoxy varnish coating exhibited a rapid decrease in impedance with immersion time and essentially lost its protective capability after 480 h.In contrast，the intact coating containing washed microcapsules showed only slight impedance variation during 1 200 h of immersion，maintaining values above 1010 Ω∙cm2.For coatings with defects，the impedance of the epoxy varnish was only 108 Ω∙cm2 at the beginning of immersion and decreased rapidly thereafter.However，defect-containing coatings with directly added or wash-and-dry-treated microcapsules exhibited initial impedance values close to 1011 Ω∙cm2 due to the self-healing effect of the microcapsule core，demonstrating significantly improved protection.These results indicated that the incorporation of polyaniline microcapsules enhanced the protective performance of epoxy coatings on magnesium alloys.Among the three posttreatment methods，washing the as-polymerized microcapsule emulsion prior to incorporation yielded the best overall protective performance.

To improve the hardness and wear resistance of NiCr-based alloys，NiCr-based alloys reinforced with WC and TiB2 were respectively overlay welded by gas metal arc welding.The microstructure and chemical composition of the deposited layers were analyzed using optical microscopy，scanning electron microscopy(SEM) and energy-dispersive spectroscopy(EDS).The phase composition of the deposited layers was characterized by X-ray diffraction(XRD)，and their microhardness was measured using a Vickers hardness tester.Results showed that in both WC-and TiB2-reinforced NiCr-based alloys，large amounts of carbides such as M23C6 and M7C3 were distributed within the γ-Ni solid solution.Both WC and TiB2 played a role in refining the M23C6 and M7C3 grains.However，TiB2 exhibited a more pronounced grain-refining effect due to its smaller particle size and higher density of heterogeneous nucleation sites.The addition of WC and TiB2 both increased the hardness of the NiCr-based alloy.The hardness of the alloy containing 9%(mass fraction) WC was slightly lower than that of the alloy containing 4%(mass fraction) TiB2，with the latter reaching an average hardness of 479－480 HV under a load of 1 N and a dwell time of 10 s.Regardless of whether WC or TiB2 was added，cracks were observed on the surface of the deposited layers，and pores were present within the deposited layers.

To investigate the corrosion differences of commonly used buried structural steels in different soil environments and to provide a theoretical basis for selection of buried materials in different regions，the corrosion performance，corrosion morphology and corrosion products of Q355B steel in typical soil environments of Wuhan and Korla were comparatively analyzed using weight loss method，scanning electron microscopy(SEM)，energy dispersive spectroscopy(EDS) and X-ray diffraction(XRD).Additionally，the corrosion behavior of Q355B steel in the two soils was also studied combined with electrochemical analysis.Results showed that Q355B steel in the soil environment of Korla exhibited general corrosion，with more severe corrosion and a weight loss approximately 1.65 times that of Wuhan soil.In contrast，localized pitting corrosion was more pronounced in Wuhan soil，with an average pitting depth 1.25 times greater than that in Korla soil.The corrosion products of Q355B steel in the two types of soil were mainly oxides of Fe，including α-FeOOH，γ-FeOOH and Fe3O4.Overall，the differences in soil types led to variations in the protective properties of corrosion products of Q355B steel.

The composite treatment of MoS2 coating and anodic oxidation is widely applied to the surface lubrication of fasteners such as bolts.However，its evolution law of lubrication performance under corrosion and high-humidity conditions in coastal environments has not yet been investigated.In this study，MoS2-coated plates and bolts were subjected to 3 500 h of neutral salt spray corrosion.After corrosion，reciprocating friction tests on the plates and torque coefficient tests on the bolts were conducted to measure the reciprocating friction coefficient and torque coefficient，thereby establishing the evolution law of friction coefficient.Meanwhile，combined with the observation of wear morphologies，the underlying reasons for the evolution of the bolt friction coefficient and torque coefficient were revealed.The wear mechanism of the coating after salt spray corrosion was proposed.Results showed that as the corrosion duration increased from 0 h to 3 500 h，the average sliding friction coefficient of the MoS2-coated plates changed only slightly during the reciprocating tests.Samples treated with the composite treatment of anodizing and MoS2 coating exhibited a significant decrease in friction coefficient after corrosion.Salt spray corrosion induced oxidation of the MoS2 coating，leading to the formation of hard oxide particles that caused plowing and abrasive wear，ultimately resulting in flake-like spallation of the coating.This spallation exposed the underlying substrate or oxide layer to the friction pair，thereby altering the friction curves.Additionally，salt spray corrosion increased both the thread friction coefficient and the friction coefficient of the bolt bearing surface，leading to higher overall friction and torque coefficients.Bolts treated with the composite anodizing and MoS2 coating exhibited improved low-friction stability and service reliability under salt spray corrosion，providing key experimental evidence and theoretical support for optimizing surface treatment processes and achieving long-term lubrication protection for bolt fasteners in coastal regions.

Aluminum alloys are often used as cementing attachment materials for oil drilling，but with the increase in drilling depth and the coupling of downhole environmental factors(e.g.，high temperature，strong alkali，high salt)，aluminum alloys often suffer from severe corrosion.In order to improve the corrosion resistance of aluminum alloys，WC coatings were prepared on the surface of 2A12 substrate by spraying technology，and the corrosion tests were carried out for different times(12，24，36，48 h) under the conditions of pH＝14，220 ℃ and 30%NaCl.Characterization methods，such as X-ray diffraction(XRD)，scanning electron microscopy(SEM) and energy-dispersive spectroscopy(EDS)，were used to systematically analyze the corrosion products and corrosion morphology.Results showed that as the corrosion time was extended，the corrosion rate exhibited a trend of first increasing and then decreasing.Within 12 h of corrosion，the WC coating effectively protected the 2A12 substrate.However，as the corrosion time increased，corrosive ions penetrated into the substrate，leading to the formation of a significant amount of corrosion products on the coating surface.After the WC coating was prepared，the corrosion current density decreased from 3.53×10－4 A/cm2(2A12) to 4.77×10－6 A/cm2(2A12/WC)，providing effective protection for the substrate.Nevertheless，owing to the substantial difference in the coefficients of thermal expansion between the 2A12 aluminum alloy and WC，as well as the inherent pore and crack defects within the sprayed WC coating，pathways were created for corrosive ions to infiltrate the substrate.As a result，the coating experienced delamination and failure after prolonged exposure(36 h) to the harsh downhole environment.

To investigate the effect of Ni on the microstructure and corrosion resistance of Fe20Cr8Si alloys，the Fe20Cr8SixNi(x＝0，1，2，3，4) alloys were prepared using a vacuum arc furnace.Microstructural observation，electrochemical corrosion tests，and chemical immersion corrosion tests were employed to systematically investigate the changes of the microstructure and corrosion resistance of Fe20Cr8Si alloys after adding different contents of Ni.Results showed that after adding Ni to the Fe20Cr8Si alloy，the microstructure of the alloy did not change and remained an(Fe，Cr) solid solution with a BCC equiaxed grain structure.However，as the Ni content in the alloy increased，the amount of Ni dissolved in the alloy rose，which led to a corresponding increase in the degree of grain refinement of the alloy and thus improved the microhardness of the alloy.In a 3.5%(mass fraction) NaCl solution，Ni element improved the physicochemical properties of the alloy's passive film，enhancing its continuity and stability.Consequently，the electrochemical performance of the alloy increased as the Ni content within the alloy rose.After immersion in a 10%HCl solution for 168 h，the corrosion layer of the Fe20Cr8Si4Ni alloy exhibited the highest density，resulting in reduced contact between the corrosive medium and the substrate，minimal mass loss and optimal corrosion resistance.

To investigate the effect of lignin on the properties of base lithium-based grease，the performance of the grease containing lignin was evaluated using a thermogravimetric analyzer(TGA)，a differential scanning calorimeter(DSC)，a four-ball friction tester，a fretting friction and wear tester(SRV) and a scanning electron microscope(SEM).Results showed that lignin significantly enhances the thermal stability，oxidation resistance and tribological properties of lithium-based grease.When the lignin content reached 10%(mass fraction)，the thermal decomposition temperature of the grease composition increased to 374.9 ℃，and the wear volume decreased by 60%.XPS was used to explore the lubrication mechanism，which revealed that the lubrication mechanism of lignin involved two aspects.First，the macroscopic particles filled the microcracks generated by friction and could roll between the contact interfaces，converting sliding friction into rolling friction.Second，the active phenolic hydroxyl groups in lignin's molecular structure adsorbed onto the iron surface，forming a friction/adsorption film that prevented direct contact between the metal friction pairs.This improved the tribological performance and load-carrying capacity of the grease.Therefore，the introduction of lignin could significantly improve the lubrication performance of lithium-based grease.

To address the high-temperature corrosion challenges of carbon steel equipment in oilfield downhole，this study synthesized a novelalkyl-imidazole corrosion inhibitor(13-BIP) from 2-aminobenzimidazole and 4-tridecyloxybenzoic acid via an amidation reaction and encapsulated it in alginate hydrogel using a one-pot method(SA＠13-BIP).The study confirmed the successful synthesis of 13-BIP through Fourier transform infrared spectroscopy(FT-IR) and proton nuclear magnetic resonance(1 H-NMR) tests.Electrochemical impedance spectroscopy(EIS) and potentiodynamic polarization curve tests showed that the corrosion inhibition efficiency of Q235 carbon steel immersed in an acidic oilfield solution containing the mixed corrosion inhibitor 13-BIP could reach 86.81% at 90 ℃.In addition，scanning electron microscopy(SEM) and X-ray photoelectron spectroscopy(XPS) tests were conducted on the surface of carbon steel treated with the 13-BIP solution.The results indicated that the 13-BIP corrosion inhibitor formed a self-adsorbed film on the carbon steel surface，primarily through chemical adsorption.Moreover，settlement and release tests demonstrated that the release rate of SA＠13-BIP reached 30.85%in the working area at the bottom of an oil well exceeding 2 000 m in depth.Additionally，long-term impedance test results showed that the corrosion inhibition effect duration of SA＠13-BIP was extended to over 24 h compared to the use of the 13-BIP corrosion inhibitor alone.In general，this study successfully synthesized and prepared a thermally stable imidazole corrosion inhibitor and an alginate gel sustained-release capsule，providing a solution for the long-term protection of carbon steel in high-temperature environments.