Microorganisms are abundant in the environment and have shown great potential in inhibiting corrosion due to their advantages such as large-scale proliferation, gene editing, and environmental response. This paper first reviews the research progress on different mechanisms of microbial corrosion inhibition at home and abroad, summarizes the types of microorganisms that induce mineralization and several typical types of mineralization products that have been discovered so far, and elaborates on the mechanism of microbial mineralization for corrosion inhibition. It focuses on analyzing how to artificially intervene in microbial-induced mineralization through strategies such as optimizing nucleation sites, changing environmental factors, controlling urease expression, and 3D printing to achieve long-term corrosion protection. Finally, it summarizes the challenges faced by microbial mineralization for corrosion inhibition technology and proposes prospects for optimizing this technology.

Carbon dots (CDs) have become a research hotspot in the research on novel nano-scale green corrosion inhibitors due to their outstanding photoelectric properties, abundant sources, rich functional groups and heteroatoms, as well as their environmentally friendly characteristics. Based on the structural properties of CDs, this paper summarizes the specific methods for synthesizing CDs through top-down and bottom-up approaches at present, and briefly introduces the application of theoretical calculation in the synthesis of CDs. The corrosion inhibition performance of three types of CDs corrosion inhibitors on different metals in various media was analyzed, and their action modes in solutions, and the relevant inhibition mechanism were discussed. They are respectively based on doping (non-metallic, metallic and co-doping), surface modification and biomass as substrate, which are the CD corrosion inhibitors that have attracted much attention so far. Furthermore, the future development trends are prospected. It is expected that this review may provide important references for future the in-depth research and practical application of CDs-based corrosion inhibitors and promote the high-quality development of metal corrosion protection technology.

Metal corrosion has caused significant losses to the national economy. Corrosion not only shortens the service life of industrial facilities but also poses potential threats to environmental safety. To address these challenges, light-responsive self-healing coatings, as a special functional smart material, have emerged. These coatings can self-repair under light irradiation, thereby restoring the integrity and other properties of the coating. Herein, the classification, mechanisms, and corrosion protection applications of multifunctional light-responsive self-healing coatings are reviewed, aiming to explore and address challenges in the field of corrosion protection, improve the safety and reliability of facilities, reduce maintenance frequency and costs, and provide new ideas and technical support for equipment protection in extreme environments. It discusses the latest domestic and international research achievements regarding the enhancement of corrosion resistance, anti-icing, and early warning performance of light-responsive self-healing coatings. It also analyzes in detail the influence of factors such as filler content, light wavelength, light intensity, and substrate type on the self-healing performance and corrosion resistance of the coatings. Finally, a series of optimization suggestions are proposed to address current issues such as high coating preparation costs and low photothermal conversion efficiency, and look forward to the broad application prospects of light-responsive self-healing coatings in corrosion protection of industrial equipment and pipelines, routine maintenance and fault prevention, adaptability to complex environments, and integration with new energy technologies.

With the rapid expansion of China's highway network, winter precipitation in northern regions poses significant challenges to the transportation safety. De-icing agents have the advantages of simplicity in operation, and high efficiency in melting ice and snow in comparison to the mechanical snow removal, thus greatly enhance the convenience of traffic. However, the long term use of traditional chloride-based de-icing agents (NaCl, CaCl₂, MgCl₂, etc) will cause corrosion and failure of rout surface and other infrastructures and also causes irreversible damage to the environment. This paper systematically analyzes current standards for de-icing agents at home and abroad, a critical assessment was made of the formulations, actual application processes and limitations of conventional chloride-based and alternative non-chloride de-icing agents, and further reviews the recent advancements in eco-friendly composite de-icing technologies. Particular emphasis is placed on innovative material combinations that leverage synergistic effects between components to enhance ice-melting efficiency while minimizing environmental impact. The review concludes with a forward-looking perspective on sustainable development strategies for next-generation de-icing formulations, addressing critical needs for infrastructure preservation and ecological protection. We hope the paper could provide some critical insights to guide the rational design of high-performance, environmentally benign composite de-icing agents.

As an emerging lightweight, high-temperature structural material, TiAl alloy holds broad application prospects in the aerospace field. However, its insufficient oxidation resistance limits its further application. In this study, a novel solvothermal liquid-phase fluorination treatment technique was applied to introduce a fluorinated layer on the surface of Ti45Al8.5Nb alloy, in order to promote the in-situ growth of a dense Al₂O₃ oxide layer on the alloy surface, thereby enhancing its high-temperature oxidation resistance. The oxidation behavior, as well as the composition and structure of the oxide layer, of the Ti45Al8.5Nb alloy after liquid-phase fluorination treatment were investigated in air at 900 ^oC. The results indicated that the liquid-phase fluorination treatment can significantly reduce the oxidation rate of the Ti45Al8.5Nb alloy. After oxidation at 900 ^oC for 100 h, the weight gain of the fluorinated alloy decreased from 1.12 mg·cm^-2 (for untreated ones) to 0.45 mg·cm^-2. The treatment facilitated the formation of a continuous and protective dense scale Al₂O₃ on the alloy surface, effectively suppressing the inward diffusion of oxygen and thereby significantly enhancing the alloy's high-temperature oxidation resistance.

The corrosion behavior of Inconel 718 alloy without and with a pre-deposits film of salt mixture of 75%Na₂SO₄ + 25%NaCl at 750 ^oC was assessed, in various atmospheres such as air, air-30%H₂O, CO₂ and CO₂-30%H₂O, respectively. The results show that the bare Inconel 718 alloy exhibits outstanding oxidation resistance in the atmospheres: air, CO₂ and CO₂-30%H₂O, and the oxidation products scales are principally composed of a uniform and continuous Cr₂O₃ scale. The corresponding thickness of which is 0.4 ± 0.1, 1.2 ± 0.1 and (0.7 ± 0.1) μm, respectively. Beneath a salt deposits film, the alloy displays poor hot corrosion resistance in air, and the corresponding thickness of the corrosion products scale is (10.2 ± 2.9) μm. The corrosion became more serious as the alloy with pre-deposits film of salts mixture is exposed to air-30%H₂O, and the thickness of the corrosion scale increases to (12.3 ± 3.6) μm. In the above two environments, the formed corrosion products scales are composed of Cr₂O₃ and minor Fe₂O₃. In addition, these scales are loose and porous, accompanied with severe spallation and internal sulfidation. Nevertheless, the alloy with pre-deposits film of salts mixture exhibits superior resistance against the hot corrosion induced by the salts mixture + atmosphere CO₂-30%H₂O. Correspondingly, the corrosion products scale is a continuous Cr₂O₃ scale of only (1.7 ± 0.4) μm in thickness, which provides sufficient protection for the alloy against the aggressive environment.

The wire beam electrode technique was systematically employed to investigate the evolution of atmospheric corrosion behavior on carbon steel surfaces under droplets with varying conductivities in laboratory-simulated environments. The experimental results showed that with increasing corrosion time, the local anodic and cathodic currents on the carbon steel surface gradually increased under low-conductivity droplets, while both currents gradually decreased under high-conductivity droplets. When the NaCl concentration inside the droplet was 0.001 mol/L, the anodic and cathodic distributions on the electrode surface appeared relatively random during the initial stage of the experiment. However, when the NaCl concentration exceeded 0.003 mol/L, the distribution of anodic and cathodic currents on the electrode surface exhibited the typical characteristics of the Evans model. Further research revealed that variations in droplet conductivity significantly influenced the mechanisms by which macro-cell and micro-cell currents affected the overall corrosion rate. Under low-conductivity conditions, the macro-cell currents in the cathodic region played a protective role, effectively preventing corrosion. In contrast, under high-conductivity conditions, the cathodic region underwent significant corrosion due to the action of micro-cell currents.

In this paper, the long-term anticorrosion performance in 3.5%NaCl solution of 10# mild steel and LY12 Al-alloy coated with the same single-component fluorocarbon-modified epoxy coating, was comparatively studied by means of electrochemical tests such as open-circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curve, and macro/micro morphology characterization as well as adhesion test and water contact angle test. The results showed that the modified epoxy coating shows better corrosion resistance when applied on LY12 Al-alloy rather than applied on 10# mild steel by long-term immersion in 3.5%NaCl solution for 3500 h. The failure of the modified epoxy coating on the surface of the two substrates can be divided into four and three stages respectively, and the failure process is different. The corrosion of the coating/metal interface is the key to determine the failure rate of the coating. Low coating adhesion and high water contact angle for the coating on Al-alloy and high coating adhesion and low water contact angle for the coating on carbon steel substrate are the main reasons for the different failure courses of coatings.

To enhance the corrosion resistance of austenitic stainless steel in molten Pb-Bi alloy eutectic, herein, hot-rolled plates of alumina-forming austinite (AFA) steels with varying Al contents (3.5%-4.5%, mass fraction) are made and pre-oxidized in air at 800 ^oC for 20 h. Then their corrosion performance was comparatively assessed in oxygen-saturated Pb-Bi alloy eutectic at 600 ^oC up to 10,000 h via static immersion test, surface and cross-sectional morphology observations, along with compositional analysis of the formed oxide scales. Results demonstrate that the corrosion resistance to molten Pb-Bi alloy eutectic of AFA steel increases with the increasing Al content, especially, the steel with 4.5%Al exhibits superior corrosion resistance with a damage area ratio less than 20% for its pre-formed Al₂O₃ scale. In fact, this phenomenon may be ascribed to that during the long-term corrosion process, due to the existence of weak local spots within the pre-formed Al₂O₃ scale, where micro-defects will be generated, at the same time, the NbC particles on the surface may be oxidized to Nb₂O₅, which can further induce microcracks in the surrounding Al₂O₃ film. These provides a rapid pathway for the inter-diffusion of alloying elements and O, leading to localized internal oxidation and causing the pre-formed Al₂O₃ scale to be damaged. The findings reveal the critical mechanisms governing long-term corrosion performance of the pre-oxidized AFA steels in molten Pb-Bi alloy eutectic cooled nuclear systems.

The inherent surface film resulted from the manufacturing process on the as received B30 Cu-Ni alloy may affect its corrosion behavior, especially the initial stage of corrosion, but there is a lack of methods to quickly evaluate such influence. In this paper, the initial corrosion behavior in seawater of two B30 Cu-Ni alloys of more or less the same chemical composition but with different inherent films resulted by different manufacturing process were studied via immersion test with EIS and Mott-Schottky measurement, as well as SEM and XPS etc. The results show that the presence of Ni oxide and carbon film in the inherent film leads to a higher initial corrosion potential and higher impedance of B30 Cu-Ni alloy with the inherent film rather than that has the film removed, which is not conducive to the rapid formation of a corrosion products film on B30 Cu-Ni alloy in seawater. In particular, when elemental carbon exists in the inherent film, the potential difference between the surface film and the substrate can be maintained for a long time, thus a "large cathode and small anode" will be formed between the surface film and the substrate. This condition leads to localized corrosion of the substrate, significantly reducing the corrosion resistance of B30 Cu-Ni alloy. When the free corrosion potential of the B30 Cu-Ni alloy withinherent film is negative or can be reduced within 1 h and maintained below -0.1 V during corrosion process, a passive film with good corrosion resistance may form on the B30 Cu-Ni alloy surface. When the free corrosion potential of the B30 Cu-Ni alloy with inherent film is positive and maintained for a long time, pitting is easy to occur, which is not conducive to the corrosion resistance of B30 Cu-Ni alloy. It follows that the characteristics of free corrosion potential and its evolution of B30 Cu-Ni alloy with inherent films can be used as an index to evaluate the influence of the inherent films on the corrosion resistance of B30 Cu-Ni alloy.

In order to investigate the formation mechanism of dual inductive loops in electrochemical impedance spectroscopy (EIS) of Mg-alloy, the corrosion behavior in 3.5% (mass fraction) NaCl solution of pure Mg (exhibiting uniform corrosion) and AZ31 Mg-alloy (predominantly undergoing localized corrosion) was comparatively assessed. After immersion in 3.5% (mass fraction) NaCl solution for 24 h, the EIS test results revealed that the pure Mg did not exhibit dual inductive loops. However, the dual inductive loops can be observed for AZ31 Mg-alloy. Morphological analysis further demonstrated that the pure Mg did experience uniform corrosion. However, AZ31 Mg-alloy suffered from both filiform corrosion and pitting corrosion. The different propagation mechanism of filiform corrosion and pitting corrosion led to the formation of non-uniform corrosion morphology. The test results of EIS and corrosion morphology established that the formation of double induction loops for AZ31 Mg-alloy is related to the non-uniform corrosion morphology.

10CrNi5MoV low-alloy high-strength steel may experience severe hydrogen embrittlement in deep-sea environment, while subjected to stress and cathodic protection. Hence, the hydrogen embrittlement susceptibility of 10CrNi5MoV high-strength steel in the simulated shallow sea (0 m) and deep sea (1000 m) environments by applied polarization potentials was assessed via potentiostat, electrochemical impedance spectroscopy (EIS), slow strain rate tensile (SSRT) and scanning electron microscopy (SEM). With the applied cathodic polarization potential negatively dropped from open circuit potential to -1050 mV, the hydrogen embrittlement susceptibility coefficient of the steel is about 25% in the shallow sea environment. However, which in the deep-sea environment reaches 59.7%. Although the corrosion and hydrogen evolution reactions are suppressed to certain extent in the deep-sea environment, whereas the diffusion of hydrogen atoms inwards the material is promoted, therewith the hydrogen embrittlement susceptibility of the steel is enhanced under cathodic protection.

The effect of NaCl on the corrosion behavior of 347H stainless steel and GH3539 nickel-based alloy in molten (Na, K)NO₃ at 600 ^oC has been investigated. It is shown that the addition of NaCl can markedly accelerate the corrosion of 347H and GH3539 in the melt, with a more pronounced effect on 347H. In molten (Na, K)NO₃, 347H can form a Cr-rich oxide scale, while GH3539 produces layered products composed of an outer NiO, a middle metallic Ni, and an inner internal oxidation layer. When NaCl is added to molten (Na, K)NO₃, chlorine produced by the reaction between NaCl and oxides formed on the alloy surface diffuses into the alloy matrix, giving rise to chlorination reactions of alloying elements. This chlorine-induced corrosion weakens the bonding between the oxide scale and the alloy matrix, ultimately leading to accelerated corrosion of both alloys, with the effect enhanced by higher NaCl content.

In the harsh marine environment, various metallic materials in service are subjected to varying degrees of corrosion damage, significantly impacting marine ecosystems and economic efficiency. While the mechanisms of microbial corrosion in shallow marine environments have become a focal point of international research, with substantial progress made in theoretical frameworks and experimental data accumulation, the understanding of microbial corrosion mechanisms under the unique conditions of deep-sea environments remains limited. This study focuses on the effect of deep-sea piezotolerant bacteria on the corrosion of 2205 duplex stainless steel in M. piezotolerans bacteria containing media at 28 ^oC, namely the optimal growth temperature of that bacteria, aiming to provide theoretical support for microbial corrosion research on metallic materials in deep-sea environments. The M. piezotolerans bacteria used in this study, was isolated and purified from sampling sediments from the South Pacific Gyre. Characterization techniques such as confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), X-ray photoelectron currents. The uniform corrosion rate was reduced; however, small pitting corrosion sites were observed on the spectroscopy (XPS), and electrochemical impedance spectroscopy (EIS) were employed to examine the corrosion behavior of 2205 duplex stainless steel in the presence of M. piezotolerans. The results demonstrated that the presence of M. piezotolerans may facilitate the formation of a three-dimensional structured corrosion products film on the steel surface. Compared to sterile solutions, steels in M. piezotolerans culture exhibited lower impedance values and higher corrosion rate. Overall, the biofilm formed in the presence of M. piezotolerans on 2205 duplex stainless steel could partially inhibit the uniform corrosion of the steel but exacerbated localized corrosion, resulting in the formation of distinct pitting sites on the steel surface.

Amido-group triazine quaternary ammonium salt (CCDY) corrosion inhibitor was synthesized by nucleophilic substitution reaction and quaternary ammonium reaction with trichlorotriazine, dipropylamine and bromoacetamide as raw material. Then which was compounded with thiourea (TU) and sodium tungstate to acquire the complex inhibitor of optimal proportion, which was named CTLY. Next, the corrosion inhibition performance of the complex corrosion inhibitor CTLY for Q235 steel was assessed via static immersion test at 90 ^oC in 0.5 MPa CO₂ containing 3.5%NaCl solution, accord with an orthogonal test arrangement, as well as electrochemical tests, surface morphology analysis and quantum chemical calculations. The results show that the corrosion inhibition rate of CTLY for Q235 steel can reach 96.64%. CTLY conforms to the Langmuir adsorption isothermal formula on the surface of Q235 steel, and the standard adsorption Gibbs free energy (ΔG⁰) is between -20 and -40 kJ/mol, correspondingly which is a mixed adsorption dominated by chemical adsorption. Electrochemical tests showed that CTLY was a mixed inhibitory corrosion inhibitor, while mainly inhibiting the anode reaction. The Nyquist plot shows a single-half arc, and the charge transfer impedance increases significantly with the increase of CTLY concentration. The surface morphology analysis further showed that CTLY had a good corrosion inhibition effect.

Currently, oil well tubing and surface pipelines are facing severe risks of microbial corrosion (MIC). Microorganisms can multiply in fracturing fluids, drilling muds, and formation water, resulting in significant corrosion and clogging of oil well tubing and surface pipelines, and other accidents, which seriously affect oil and gas production and safety. Ti-alloy has the advantages of corrosion resistance and high strength, but its antimicrobial properties require further investigation. This article, a novel Cu-containing Ti-alloy TC18-0.5Cu was made by vacuum arc melting, which then subjected to 800 ^oC solid solution treatment (ST800), 800 ^oC SS treatment plus 580 ^oC aging treatments (ST800AG580), and 800 ^oC SS treatment plus 620 ^oC aging treatment, respectively. Futher, the antimicrobial performance of the three alloys was assessed in sulfate-reducing bacteria (SRB) containing artificial formation waters, meanwhile the growth of sulfate-reducing bacteria (SRB) was analyzed by surface morphology and biofilm thickness, and the bactericidal rate of the Ti-alloys was calculated based on the results of the confocal microscope shots. The results showed that the sterilization rate of the three copper-containing Ti-alloys with different heat treatments could reach more than 75%, suggesting that the heat treatment processes had no significant effect on their sterilization effect. The antimicrobial property of the copper-containing Ti-alloy is due to the fact that the Cu in the alloys is dissolved in the corrosive environment, and the Cu ions destroy the bacterial membrane of bacteria such as SRB, thus inhibiting the growth of bacteria. Furthermore, electrochemical tests revealed that the addition of a small amount of copper, combined with a suitable heat treatment process, also improved the corrosion resistance of the alloy.

During the voyage of polar ships, the coating of the ship's hull may peel off due to the erosive action of sea ice, thereby leading to the coupled effect of sea ice friction and seawater corrosion. Herein, the performance of FH40 polar marine low-temperature steel with two different microstructures in conditions of artificial sear-water corrosion, sea-ice wear and friction, as well as the coupling effect of sea-water corrosion and sea-ice friction at different temperatures was assessed via a simulation set, electrochemical techniques, in terms of the microstructure and the variation of wear trace characteristics for the test steels, as well as light interferometer and scanning electron microscope, in terms of the microstructure and wear trace characteristics of the test steels The results indicate that as the grain size of steel increases, there are significant changes in the friction coefficient and corrosion rate by the same test conditions, namely increasing from 0.28 to 0.35 for friction in air at 20 ^oC; from 0.23 to 0.25 for friction in artificial seawater at 20 ^oC; from 0.38 to 0.43 for friction in air at 0 ^oC; and from 0.29 to 0.32 for friction in artificial seawater at 0 ^oC; The corrosion rate increased from 3.11 × 10^-3 to 3.86 × 10^-3 mm/a in artificial seawater at 20 ^oC; However for immersion in artificial seawater at 0 ^oC the corrosion rate of the steel of fine grains is 2.11 × 10^-3 mm/a, while that of coarser rise to 2.76 × 10^-3 mm/a. This may be ascribed to that fine grains can result in higher hardness of the steel, increase the resistance to dislocation movement and plastic deformation, thus make the steel stronger wear- and corrosion-resistance. During friction test while free corrosion in artificial seawater of the steel, it was found that with the progress of corrosion process the cross-sectional width of wear marks increased, the wear amount increased, and the corrosion potential shifted to the negative direction. The calculated wear increment W_C caused by corrosion and the corrosion increment C_W caused by wear were both positive, providing favorable evidence for the coupling and mutual promotion of friction and corrosion.

7075 Al-alloy is subjected to the dual effects of wear and corrosion in marine environment, resulting in long-term accumulation failure, which causes a serious threat to the safety and efficiency of offshore operations. However, the mechanism by which wear and corrosion affect the corrosion behavior of 7075 Al-alloy is still unclear. Hence, the wear and corrosion behavior of 7075 Al-alloy was studied in conditions of varying pressure load and friction frequency in terms of the coefficient of friction (COF), open circuit potential and potentiodynamic polarization, meanwhile the s morphology and composition of the friction-wear scars was examined by SEM image and the results of EDS. The main conclusions are as follows: COF values increase to different degrees under different friction frequencies and different pressure loads. Compared to static corrosion environment, the current density of 7075 Al-alloy under friction condition increases significantly by 2-3 orders of magnitude. When the friction force is relatively low (5 N-0.01 Hz and 5 N-0.10 Hz), the mechanism is abrasive wear; when the friction force is relatively high, it is adhesive wear, which is manifested as a large-particle tearing morphology. Therefore, the loss of materials caused by wear and corrosion is not a simple superposition of static corrosion and mechanical wear.

The failure behavior of glass fiber reinforced polymer (GFRP) in high temperature and high humidity environments, i.e. 60 ^oC-80%RH, 60°C-95%RH, and 80 ^oC-95%RH was investigated by tensile, compressive, flexural, and impact mechanical property tests, combined with morphological characterization, infrared spectral analysis, and moisture absorption rate test. The results show that in high temperature and high humidity environments, humidity mainly affects the saturated water absorption of GFRP, and temperature mainly contributes to the increasing water diffusion coefficient, which leads to the most serious damage to GFRP at 80 ^oC-95% RH. The aging degree of GFRP shows no obvious difference in the other two environments of 60 ^oC-80%RH and 60 ^oC-95%RH. Among the results of tensile, bending, compression, and impact performance test, those of the compression test reveals that the most significant decline in compressive strength of GFRP immerged at 60 ^oC-80%RH and 60 ^oC-95%RH, decreasing by 18.18% and 22.22% respectively after 49 d of aging. This may be attributed to the dissolution and plasticization of the resin matrix after water absorption by GFRP; Those of the impact strength test shows that the most significant decrease in impact strength of GFRP occurred at 80 ^oC-95% RH, decreasing by 51.43% after 49 d of aging, which is mainly due to the destruction of the resin/fiber interface.

The influence of temperature on the corrosion behavior of J55 petroleum casing steel in an artificial CO₂-containing formation water was studied by immersion test at 25, 0 and -20 ^oC for 10, 30, and 50 d respectively. The results indicate that the corrosion rate of J55 steel at different temperatures decreased in the initial stage and then increased with prolonged immersion time. The highest corrosion rate was observed at 25 ^oC, while the lowest occurred at -20 ^oC. XRD analysis revealed that the corrosion products on the steel consisted mainly of FeCO₃, along with Fe₂O₃, α-FeOOH, and γ-FeOOH. SEM results showed that after corrosion at ambient temperature for different immersion periods, the steel surfaces were covered with a loose and porous rust layer after, whereas at low temperatures, fewer corrosion products adhered to the surface, mostly as agglomerated clusters. 3D surface topography analysis demonstrated that all the test steels exhibited pitting corrosion characteristics. Furthermore, with the increasing immersion time at different temperatures, both the depth and maximum volume of the corrosion pits progressively increased.

Due to the complex corrosion environment of CO₂ flooding production wells, there are many corrosion failure cases of tubing in the harsh oil well environment. A comprehensive analysis of failed tubing is helpful to clarify the causes of failure and propose effective protective measures. In this work, the failure behavior and mechanism of N80 tubing in the CO₂ flooding production wells are studied by characterizing their microstructure, mechanical properties, corrosion products and surface morphology. The results show that the sulfide stress corrosion cracking of N80 tubing may be caused by the high concentration of Cl^-, H₂S, CO₂ and other substances in the production well liquids and the combined effect of the existed stresses. Crevice corrosion of tubing may be induced by the galvanic effect in the existed crevices inside and outside of the threaded coupling, of which the synergistic effect with stress can also enhance the stress corrosion cracking susceptibility of tubing. Microcracks initiate in pits with high stress concentration on the thread surface and extend to the inner wall. Cl^- and sulfides are enriched at the bottom of the pits, the crack tip and the bottom of the thread, providing a driving force for crack propagation. Finally, the cracks quickly penetrate the pipe wall, resulting in brittle fracture and failure of N80 tubing.

Bulk GH4099 alloy was fabricated through a specific SLM process, then subjected to appropriate heat treatment. The hot corrosion behavior of the prepared bulk GH4099 alloys with and without heat treatment was comparatively assessed beneath a thin deposits of 75%Na₂SO₄ + 25%NaCl in air at 900 ^oC by means of electronic analytical balance, optical microscopy (OM), X-ray diffractometer (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectrometry (EDS) etc. The results reveal that the micron-sized cellular sub-grains and MC carbides are detected in the SLM alloy. After heat treatment, the grains grow and new phases precipitate. The corrosion kinetics analysis indicates that the bare and heat treated SLM alloys experience more or less the same weight loss in the initial stage, and in the later stage, the two SLM alloys all show obvious corrosion. The corrosion products are divided into four layers, and the hot corrosion process follows an acid dissolution mechanism. The heat-treated alloy has better hot corrosion resistance due to the formation of M₂₃C₆ and γ′ phases.

Silicide coating is often used as the main component of oxidation resistance coating on Mo-alloy due to the formation of SiO₂ glass phase during high temperature service. At present, slurry method is widely used to prepare silicide coating on Mo-alloy surface due to easy operation and no-need for large equipment. However, the binder content in slurry method and its effect on the microstructure and oxidation resistance of the coating are still unclear. In this paper, silicide coatings with different binder contents were prepared on TZM Mo-alloy surface by slurry sintering method. The microstructure and phase composition of silicide coatings prepared with different binder PVB contents were studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD), and then the oxidation resistance of Mo-alloy with coating was examined in air at 1000, 1100 and 1200 ^oC for 1 h respectively. The results showed that with the increase of PVB content in the range of 2% to 10%, the number and width of cracks of the prepared coatings decreased, correspondingly the weight loss of the coatings induced by high temperature oxidation is alleviated. However, when the PVB content exceeds than 10%, there is no significant improvement in crack formation and the weight loss. In summary, the optimal effect is achieved when the PVB content is 10%.

316L stainless steel is widely used in the sulfur-containing natural gas purification equipment and pipelines. But, its welded seam and heat-affected zone may pose a higher risk of corrosion, because of their lower resistance of corrosion refer to base material. Therefore, the corrosion resistance of 316L stainless steel in welded joints is crucial to guaranteeing the safe operation of the relevant equipment and pipelines. Herein, the corrosion behavior of the substrate, welded seam, and heat-affected zone of 316L stainless steel in a simulated service condition was investigated using weight loss method, ultra-depth three-dimensional scanning microscopy, and X-ray photoelectron spectroscopy (XPS). The composition and semiconductor properties of the formed passive films were characterized using XPS and the Mott-Schottky method. The results show that, when H₂S is free, the steel exhibit very light corrosion, with a general corrosion rate of only 0.001~0.004 mm/a. The content of H₂S correlates with the corrosion rate, as the H₂S content increases, the corrosion rate also rises; for example, in conditions of 0.1 MPa H₂S at 120 ^oC, the general corrosion rate of the welded seam, base material, and heat-affected zone is 0.316, 0.472, and 0.551 mm/a, respectively, and the localized corrosion rates is 86.590, 42.757, and 60.861 mm/a. At 90 ^oC and 1 MPa H₂S, the general corrosion rate of them is 1.136, 1.001, and 0.861 mm/a, and the localized corrosion rateis 125.595, 90.297, and 124.291 mm/a. These results indicate that the welded seam is a high-risk area for localized corrosion, with the localized corrosion rate is approximately 1.4 to 2 times that of the base material. XPS results revealed that the main corrosion products were iron sulfides, iron oxides, and Cr(OH)₃. The analysis of the semiconductor properties of the formed passive films showed that the welded seam had the highest carrier concentration, making the passive film in this region more susceptible to damage, leading to an increased risk of localized corrosion.

Herein, the inhibition effect of imidazoline phosphate on the galvanic corrosion of 7075 Al-alloy in 3.5%NaCl solution was investigated by means of electrochemical tests and scanning electron microscopy as well as molecular dynamics simulation. The results indicate that the AlCuFeMn phase within the 7075 Al-alloy can induce micro galvanic corrosion effects, leading to pitting corrosion. When coupled with X70 steel, the galvanic effect significantly accelerates the progression of local corrosion. After the addition of imidazoline phosphate, the 7075 Al-alloy exhibits weak passivation characteristics, regardless of it is coupled with X70 steel or not. Notably, no obvious local corrosion occurs on the surface of the 7075 Al-alloy after immersion, suggesting that imidazoline phosphate exhibits a positive inhibitory effect on the corrosion and galvanic corrosion of the 7075 Al-alloy. Molecular dynamics simulation reveals that the adsorption energy of inhibitor molecular on the surface of Al, Fe, Cu, and Al₂O₃ is considerably higher than that of corrosive substances such as O₂, Cl^-, H₂O and H₃O⁺. This suggests that a protective film may form on the metal surface, thereby inhibiting the corrosion of Al- alloys.

The effect of passivation time of 304 stainless steel in nitrate and sulfuric acid solution on its corrosion resistance was assessed by means of electrochemical methods, in terms of the optimal passivation time, and the corrosion morphology of polarized steel. The results demonstrate that the passivation time has a significant effect on the corrosion resistance of 304 stainless steel. With the increasing passivation time, the corrosion resistance first increases and then decreases, and the corrosion resistance is the best when passivation time is 70 min. In comparison with the 70-minute passivation, the corrosion current density I_corr of the passivated film at 90 min increased from 7.032 × 10^-7 to 3.630 × 10^-6 A·cm^-2, the passivated film resistance R_f decreased from 5.514 × 10⁴ to 1.024 × 10⁴ Ω·cm², the doners density N_D increased from 2.580 × 10²⁰ to 11.47 × 10²⁰ cm^-3 and the corrosion resistance decreased.

The galvanic corrosion behavior of paramagnetic La-Fe-Si-based magnetocaloric alloys in 0.1 mol/L NaClO₄ solution under a parallel magnetic field was investigated via static immersion test, scanning electron microscopy and other techniques. The results indicate that the application of a parallel magnetic field increased the corrosion current density of the galvanic couple La-Fe and La-LaFe_13.9Si_1.4, decreased the corrosion current density of the galvanic couple La-LaFe_13.9Si_1.4. Electrochemical impedance spectroscopy and potentiodynamic polarization tests demonstrate that the parallel magnetic field can reduce the corrosion rate of La-LaFe_13.9Si_1.4. Immersion test results show that, compared with the absence of magnetic fields, the corrosion was less severe in the presence of a parallel magnetic field, with smaller and fewer corrosion pits and no obvious corrosion products. The above results were mainly ascribed to the stirring effects for the fluids caused by magnetohydrodynamic forces.

The corrosion behavior of a microbial corrosion-resistant (MIC-resistant) pipeline steel induced by sulfate reducing bacteria (SRB) was investigated through morphology observation, composition analysis, microbial culture analysis and electrochemical testing. The results show that, in the SRB environment, the number of active bacteria adhered to the surface of MIC-resistant steel is significantly reduced, and accordingly the thickness of the biofilm decreases. The MIC-resistant steel effectively inhibits biofilm attachment and growth on its surface. The MIC-resistant steel exhibited higher open-circuit potential, lower corrosion current density, and higher charge transfer resistance. There are fewer corrosion products on the surface of the MIC-resistant steel, composed mainly of dense α-FeOOH scale, in the contrast, a loose Fe₃O₄ scale may emerge on the ordinary steel surface. The corrosion rate in mass loss of an ordinary steel is approximately 1.83 times that of the MIC-resistant steel. It follows that comprehensively optimizing the content of the three alloying elements Cu, Cr, and Ni, synergistic improvement in both anti-bacterial and anti-corrosion could be achieved for this novel steel.

Sulfide is very common in special marine environments, such as microbial metabolism process, deep-sea hydrothermal area, industrial pollution area etc. In this study, the corrosion and wear process of TC4 Ti-alloy was monitored in situ by electrochemical technology, and the wear volume was quantified by step profiler and 3D profilometer. The microstructure and composition were characterized by scanning electron microscope and energy dispersive spectrometer. The effect of sulfur ion concentration on the corrosion-wear dynamic damage process of TC4 Ti-alloy in 3.5%NaCl solution was systematically revealed. The results show that the total corrosion wear amount of TC4 Ti-alloy increases significantly with the increase of sulfur ion concentrations, and the wear mechanism changes from pure abrasive wear to the composite mechanism of abrasive and fatigue wear. During the corrosion wear process, when the sulfur ion concentrations increased from 0 to 60 mmol/L, the OCP of TC4 Ti-alloy decreased by about 400 mV. At the same time, the corrosion current density increased by nearly 2 orders of magnitude. The interactive quantitative analysis of corrosion and wear shows that the proportion of corrosion-promoted wear components increased from 2.94% to 5.59%. The sulfur ion in the 3.5%NaCl solution destroyed the passivation film on the surface of the TC4 Ti-alloy, accelerated the local corrosion and aggravated the secondary dissolution of the wear scar area, which eventually led to the significant enhancement of the coupling damage effect of TC4 Ti-alloy during the corrosion wear process. This study provides an important reference for the durability design of titanium alloy components in marine equipment operating in a sulfur-containing medium environment.

In this paper, hot rolled plate of a B-containing super austenitic stainless steel S31254 was subjected to solid solution treatment at 1180 ^oC for 20 min, and then diffusion pre-treatment at 300 ^oC for different times, and finally aging 900 ^oC for 2 h. Meanwhile the influence on the precipitation of second phases during aging process and the corrosion performance in 10% NaCl solution of the aged steel was assessed. The results show that when the steel is subjected to pre-diffusion treatment at 300 ^oC for different times, it will affect the redistribution of B at grain boundaries after subsequent high-temperature aging treatment. The longer the low temperature diffusion time, the more significant the impact on the formation and distribution of the precipitation phase. Among others, the steel being pre-diffusion treated at 300 ^oC for 60 min may present the most significant inhibition effect on the precipitation of second phases. B is involved in the precipitation of the precipitated phase at grain boundaries, the B-containing Mo-rich precipitate phase interface has better corrosion resistance. After diffusion treatment at 300 ^oC for different times, the precipitates of were significantly reduced in the aging microstructure of S31254 steel.