The deep-sea environment is characterized by a multi-factor coupling of high hydrostatic pressure, low temperature, high salinity, and strong microbial activity, posing severe challenges to the safety and reliability of deep-sea equipment. Protective coatings, as a core solution, have developed into a pattern of parallel advancement of three major technical systems: metal-based coatings, modified epoxy-coatings, and intelligent functional coatings. Among metal-based coatings, traditional Zn- and Al-based alloys provide protection basically through sacrificial anodes and physical barriers, while TiAl Intermetallic compound-alloys and high-entropy amorphous alloys enhance their deep-sea corrosion resistance through structural optimization. In modified epoxy-coatings, graphene-modified coatings create labyrinthine paths for enhanced medium barrier by amino functionalization and parallel orientation. Ti₃C₂T _x and MXene coatings address galvanic corrosion through defect engineering and surface functionalization, achieving integrated protection of barrier, wear resistance, and hydrophobicity. In intelligent functional coatings, self-healing coatings complete repair through healing agents or intermolecular forces, and anti-biofouling coatings achieve a synergistic effect of anti-corrosion and anti-fouling through mechanisms such as hydration barriers and free radical sterilization. Additionally, this paper focuses on the structure-activity relationship between hydrostatic pressure and coating protection efficiency, systematically analyzing the regulatory mechanisms of pressure on medium transport, interface stability, and functional responses. Current research faces bottlenecks such as incomplete testing systems and limited engineering applications. In the future, it is necessary to develop pressure-adaptive materials, build high-pressure testing platforms, and promote customized applications to provide technical support for the long-term safe protection of deep-sea equipment.

Scanning electrochemical microscopy (SECM), a scanning probe electrochemical characterization technique based on ultra-microelectrodes (UME), enables in situ, localized, and quantitative measurements of interfacial reactions at the sub-micrometer scale. Compared with macroscopic electrochemical methods represented by polarization curves and impedance spectroscopy, SECM exhibits unique advantages in revealing spatial galvanic corrosion phenomena, corrosion inhibitor adsorption/film-forming kinetics, and multifield coupling mechanisms among coatings, substrates, and electrolytes. Herein, the latest progress of SECM application in corrosion inhibitor research was systematically reviewed, with emphasis on the significant contributions to three important fields: anti-corrosion mechanism research, research and development of corrosion inhibitors, and coating applications. In terms of anti-corrosion mechanism research, SECM has successfully elucidated the adsorption behavior, film-forming processes of corrosion inhibitors on metal surfaces, as well as their effect on electrochemical reaction kinetics, by means of various operating modes including feedback, generation-collection, and potentiometric modes. For the R & D of corrosion inhibitors, SECM has significantly accelerated the research and development process for novel inhibitors, transforming the traditional “trial-and-error method” into a data-driven, rational design approach. Endowed with capabilities of micrometer-scale spatial resolution and insitu dynamic monitoring, SECM has emerged as a pivotal characterization tool for anti-corrosion coating research. Its advantages span the entire flow scheme of coating preparation, performance evaluation, and failure analysis, with particularly outstanding performance in observing dynamic processes. Currently, challenges remain, such as the need for further improvement of scanning speed and the requirement for intelligent optimization for measurement and operation procedures.

Carbon steel has attracted widespread attention as a candidate material for metallic containers, overpacks, and related engineering components in geological repositories for high-level radioactive waste, owing to its favorable mechanical properties, engineering processability, and cost-effectiveness. During long-term repository evolution, the near-field environment is expected to transition from aerobic to anaerobic conditions, from unsaturated to re-saturated states, and from oxidizing to reducing conditions, thereby controlling the composition and phase-transformation behavior of carbon steel corrosion products. This paper reviews the phase composition, formation mechanisms, and evolution pathways of corrosion products formed on carbon steel surfaces during the initial aerobic stage, the transitional oxygen-depletion stage, and the long-term anoxic stage. It also discusses the influences of groundwater chemistry and typical components of buffer/backfill materials on the formation and transformation of corrosion products, including FeOOH, Fe₂O₃, Fe(OH)₂, Fe₃O₄, green rust, FeCO₃, and FeS. Furthermore, the potential impacts of corrosion product evolution on steel-bentonite/claystone interfacial reactions, near-field redox conditions, and the long-term performance of engineered barriers are analyzed. Finally, future research directions concerning the evolution of corrosion products on carbon steel are discussed.

Driven by global warming and rising energy demands, the carbon capture, utilization, and storage-enhanced oil recovery technology has garnered widespread attention as a crucial strategy for both greenhouse gas reduction and low-carbon energy utilization. The long-term stability of steel pipelines under supercritical CO₂ conditions is crucial for ensuring safe and reliable oil and gas field operations. Herein, the effect of factors such as water content, pressure, temperature, and flow rate on the corrosion and damage characteristics of steel pipelines was first examined. The intrinsic effect on corrosion rates and corrosion morphology was also uncovered. Subsequently, typical impurities in fluids of supercritical CO₂ were examined. Impurities such as O₂, SO₂, H₂S, NO₂, and mineral salt ions affect the composition and structure of corrosion products, as well as the stability of protective films. Their dominant roles in corrosion initiation and propagation were also revealed. Finally, the structure-function relationships and anticorrosion performance of protective materials such as inhibitors, coatings, and corrosion-resistant alloys were analyzed. Their potential and limitations in application under supercritical CO₂ conditions while in the presence of complex impurities were discussed. This study aims to clarify the corrosion and damage mechanisms of steel pipelines in the carbon capture, utilization, and storage-enhanced oil recovery project under typical environmental conditions. It may provide theoretical support for establishing long-term protection systems and ensuring safe technological operation.

Self-healing material, as a special new type of environment-responsive material, has made significant progress in material design, response mechanisms, and application expansion in recent years. In this paper the core material systems of self-healingin the field of protective coatings was introduced, including carriers such as mesoporous silica nanoparticles (MSNs), layered double hydroxides (LDHs), metal-organic frameworks (MOFs), and covalent organic frameworks (COFs), as well as functional corrosion-inhibiting active substances like organic heterocycles and amino acids. Meanwhile, the advancements in the application of self-healing materials for intelligent coatings, protection in extreme environments, and multifunctional integrated systems were summarized, and the current challenges were discussed, including high costs, insufficient long-term stability, difficulties in large-scale production, and potential environmental risks. Furthermore, the development trends for self-healing materials toward greening, multifunctionality, AI integration and collaborative management through digital twin were envisioned, so that to provide reference for the research and development of next-generation efficient and sustainable anti-corrosion technologies.

The multifield coupling environment of water, temperature, and stress in plateau permafrost regions is highly complex and poses a serious threat to the safe service and durability of infrastructure materials. In this paper, recent research findings domestic and overseas on the characteristics of the water‑temperature‑stress coupled environment in plateau permafrost regions, as well as their impact on material damage behavior were reviewed. It focuses on summarizing the coupling mechanisms among temperature, moisture, and stress fields, and outlines the influence patterns of freeze‑thaw cycles, unfrozen water migration, frost heave stress, and other factors on the performance degradation of metallic materials. Research indicates that the key factors leading to material corrosion and fracture include periodic frost-heave stress induced by the ice‑water phase transition, a high‑concentration electrolyte environment, and the synergistic effects of low temperature, mechanical stress, and electrochemical processes. On this basis, the study identifies the shortcomings in current research and proposes strategies such as deepening the understanding of multi‑field coupling mechanisms, establishing accelerated testing techniques, and developing structural steels with improved low‑temperature resistance and freeze‑thaw durability, thereby enhancing the long‑term stability of engineering facilities in cold regions. This study provides reference for the safe operation of infrastructure in plateau permafrost regions and for the development of new structural steels.

Hydrogen, as a crucial clean energy source for the future, is primarily transported on a large scale via the existing oil and gas pipeline infrastructure. Although various theories have been proposed to explain the hydrogen embrittlement (HE) mechanisms of pipeline steels, no single theory can comprehensively account for HE behavior under all service conditions. This review summarizes recent advances in the understanding of HE mechanisms about pipeline steels for hydrogen-natural gas blends, considering multidimensional influencing factors, hydrogen distribution detection, and protective technologies. The influences of environmental factors, such as temperature, pressure, and hydrogen blending ratio, intrinsic material characteristics including steel strength, microstructure, and hydrogen traps, as well as the mechanical factors like stress state, on the HE susceptibility of pipeline steels are systematically outlined. It is demonstrated that HE susceptibility in hydrogen-blended environments is not governed by a single factor. For HE detection techniques, the developments in atom probe tomography (APT), secondary ion mass spectrometry (SIMS), scanning Kelvin probe force microscopy (SKPFM), hydrogen microprint technique (HMT), and thermal desorption spectroscopy (TDS) are systematically reviewed. Furthermore, the applicability and limitations of various HE mitigation strategies, such as heat treatment, alloying, surface modification, gas inhibitors, and hydrogen-barrier coatings, are compared and analyzed. Finally, future research directions for HE prevention for pipeline steels used in hydrogen-natural gas blending are also proposed.

Mg-alloys have received much attention due to their great application potential. However, in practical engineering applications, Mg-alloys face the problems of low strength and poor corrosion resistance. Studies have shown that the addition of rare earth elements is beneficial for improving the strength and corrosion resistance of Mg-alloys. Herein, the latest worldwide research progress on high-strength and corrosion-resistant Mg-alloys were reviewed. Meanwhile the mechanisms related with the strengthening effect on the mechanical performance and enhancing effect on the corrosion resistance of Mg alloys, as well as the methods to synergistically improve the strength and corrosion resistance of Mg-alloys are analyzed and summarized in detail. It is expected to provide new ideas for the R & D of high-performance Mg-alloys.

Classification of environmental corrosion is an intuitive way to characterize the differences in the severity of material corrosion in various regions with different environmental conditions, which is of great significance for the corrosion research, the differentiated selection and the design of protection measures. In recent years, drawing corrosion map or corrosion grade distribution map of materials on the basis of environmental corrosion classification is a new research direction that closely combines the study of corrosion data with engineering application and environmental science. Corrosion map is the most direct form of environmental corrosion, which can provide data support for the anti-corrosion design, construction and operation and maintenance of engineering equipment intuitively and quickly. In this paper, the development and application status of environmental corrosion digital mapping technology were reviewed from the aspects of corrosion classification, atmospheric/soil corrosion mapping, etc., and the existing problems are also summarized.

Given that polar marine environments differ from temperate oceans by persistently low temperatures and distinctive microbial communities, a systematic understanding of the mechanical damage behavior and stress corrosion cracking (SCC) susceptibility of shipbuilding structural steels under such conditions is urgently needed. In the article a test set with controllable environmental factors was designed and made, was designed and made, which can incorporate temperature (4 ℃ and 18 ℃) and corrosive medium (air, sterile artificial seawater, and bacteria-containing artificial seawater) for simulating the service conditions of polar marine environments. Then after pre-corrosion exposure, the degradation of mechanical properties of EH40 steels was quantified, while their SCC susceptibility was evaluated by slow strain rate tensile testing (SSRT). The results demonstrate that mechanical property degradation of EH40 steel in simulated marine environments is governed by the coupled effects of temperature and microbial activity. After pre-corrosion exposure in all corrosive media, the ultimate tensile strength decreased for EH40 steels, with reductions of 2.9%-7.7%. After being subjected to corrosion in sterile artificial seawater at 4 ℃, the tensile ductility of EH40 steel was better maintained, but the elongation at break in the bacteria-containing artificial seawater was ~1.0% lower than that in the sterile artificial seawater. In contrast, at 18 ℃, pronounced ductility loss occurred in the sterile artificial seawater, whereas the bacteria-containing group showed a 4.8% recovery in ultimate tensile strength (an increase of 26.6 MPa), which may be associated with microbially induced interfacial effects (e.g., a biofilm/corrosion-product layer). The results of SSRT show that SCC of EH40 steel also exhibited strong temperature dependence. Because the SSRT duration was short, corrosion-induced cross-section loss of the test steels was limited, and their strength reduction remained below 2.2%. Nevertheless, the SCC susceptibility increased with temperature: at 4 ℃, the elongation-loss indices in sterile and bacteria-containing artificial seawater were 5.9% and 7.6%, and the reduction-in-area loss indices were 6.9% and 11.2%, respectively; at 18 ℃, the elongation-loss indices rose to 15.4% and 13.3%, and the reduction-in-area loss indices increased to 8.9% and 11.8%, respectively. The enhanced SCC susceptibility may be related to temperature-accelerated anodic dissolution, hydrogen diffusion, and microbial metabolic activity. Compared with the static tensile testing after pre-corrosion exposure, the ductility loss by SSRT was more pronounced for the steels, highlighting the dominant role of stress-environment coupling during dynamic loading, where stress concentration and hydrogen accumulation jointly promote crack initiation and propagation. These results provide a meaningful data basis for service-life assessment of polar ship structures.

During the navigation of polar ships, the propellers are subjected to frequent alternating contact with sea water and sea ice, leading to sustained impact force and corrosion on their surfaces. This synergistic effect may result in failures of marine vessel components made of steels in the simultaneous presence of corrosion and stress. Herein, the variation of corrosion resistance of low-carbon martensitic stainless steel, a candidate material for polar propellers under the effect of corrosion, stress, and corrosion-stress coupling action was comprehensively investigated via salt spray corrosion test, tensile test, and electrochemical measurement, in terms of the effect of influencing factors on the service safety of materials for polar ship propeller. Meanwhile, the surface morphology and fractured surface of the corroded steel were characterized by means of metallographic microscopy and scanning electron microscopy. The results indicate that the 0C18Cr1Ni martensitic stainless steel exhibits excellent corrosion resistance. After neutral salt spray test for 1500 h, the corrosion current density changes slightly, decreasing from 3.725 × 10^-8 A/cm² to 2.688 × 10^-8 A/cm², and the corrosion potential shifts positively from -0.2316 V to -0.2031 V in comparison to that the as received steel. The corrosion morphology on the surface of the stainless steel after the salt spray test is dominated by pitting corrosion, with pit sizes of approximately 2.04 μm after neutral salt spray test for 1500 h. However, the local pitting does not significantly reduce the tensile strength of the stainless steel; the yield strengths before and after corrosion are 270 MPa and 271 MPa and the tensile strengths are 732 MPa and 740 MPa, respectively. Subsequently, electrochemical impedance and polarization curves of a selected local area, where nearby the fracture surface of the tensile-fractured steel samples are measured. For the tensile-fractured steel sample, which has been subjected to a salt spray corrosion test for 1500 h, the corrosion current density increases to 1.388 × 10^-7 A/cm², the corrosion potential is -0.2432 V, and the corrosion rate increases from 0.0002 to 0.0016 in comparison to that of the non-spray tested ones. It follows that the corrosion resistance of the stainless steel 0C18Cr1Ni decreases significantly after corrosion-stress coupling action. It may be ascribed to that the local cracks generated by tensile stress damage the integrity of the passive film and accelerate the corrosion of the stainless steel. This study may provide a meaningful reference for the service safety evaluation and life prediction of stainless steel used in polar propellers.

In the article, NiCrAlY coatings were prepared on 304L stainless steel substrate by means of high-speed laser cladding technique. The effect of laser power variation, i.e. 4.5, 5.0 and 5.5 kW on the microstructure and high-temperature cyclic oxidation performance of the coatings were investigated. The results indicate that coatings prepared with laser power of 5.0 kW exhibit uniform grain distribution, minimal structural defects, and a pronounced <001> preferred orientation. After 112 hours of cyclic oxidation in air at 900 ℃ (holding in furnace at 900 ℃ for 8 h and then cooling down to ambient temperature as one cycle), the 5.0 kW coating demonstrated optimal oxidation resistance, with a weight gain per unit area approximately 97% lower than that of the 304L stainless steel substrate. Cross-sectional analysis indicates that the formed oxide scale consists of single Al₂O₃ phase. This may be attributed to the higher content of β-NiAl intermetallic phase (volume fraction 0.322) in the coating, which provides sufficient Al source for the continuous growth and repair of the Al₂O₃ scale, thereby significantly enhancing oxidation resistance. Furthermore, the preferred orientation <001> and high dislocation density of coatings may be beneficial further to the formation of a protective oxide scale, resulting in their superior oxidation resistance.

The chemical conversion coating was prepared on the cast AZ91D Mg-alloy with shrinkage cavities via permanganate-phosphate conversion treatment.Then the corrosion resistance of the chemical conversion coatings prepared on Mg-alloys with and without shrinkage cavities but of the same composition was comparatively assessed by means of polarization curve measurement, and salt spray test, and surface analysis techniques etc. Results show that the shrinkage cavities within cast AZ91D Mg-alloy present irregular shape of varying size and as jagged-like distributed along grain boundaries of AZ91D Mg-alloy. Their width and depth range approximately 10-300 μm and 2-8 μm, respectively. After underwent chemical conversion treatment, the coating area that happen to be located on the area with shrinkage cavities may become less compact and discontinuous, while the area proportion of the β-phase was reduced and its continuity was disrupted. These phenomena may be ascribed to that there naturally existed certain gas within the shrinkage cavity, whilst the Mg near the inner edge of the shrinkage cavity may easy react with the entering chemical conversion liquids to produce gaseous hydrogen during the chemical conversion treatment process. These gases can hinder the inward migration of chemical conversion liquids thus impeding the formation of a continuous and complete conversion film there. In addition, the shrinkage cavities can disrupt the continuity of the β-phase, which is not conducive to preventing the lateral spreading of the corrosion of the substrate beneath the conversion film, further reducing the corrosion resistance of the Mg-alloy.

An eco-friendly and highly effective extract-based corrosion inhibitor (Bidens pilosa L. extract, BPE) was successfully prepared from Bidens pilosa L. by ultrasonic extraction with water as solvent, thereby expanding its application in metal corrosion prevention. The corrosion inhibition performance and mechanism of BPE on ST12 steel in 0.5 mol/L H₂SO₄ were thoroughly investigated using the spectrum analysis, mass loss measurements, electrochemical tests, surface analysis, and quantum chemical calculations. The results show that BPE contains characteristic functional groups such as O—H/N—H and C＝O, and its corrosion inhibition efficiency can reach 85% at 30 ℃ and a concentration of 300 mg/L. BPE molecules can spontaneously form a protective film on the steel surface through physical and chemical adsorption, and the adsorption behavior conforms to the Langmuir isothermal model. Quantum chemical calculations further demonstrate a distinct structure-activity relationship between the electronic structures of key active components (flavonoids and phenolic acids) and their adsorption capacities, thus providing theoretical support for the corrosion inhibition mechanism of BPE.

Zn-Al composite coatings are widely used as protective coating for heat exchanger tube of open rack vaporizer, but suffered from corrosion damage and thus limited its service life. Enamel coatings, a high-performance inorganic non-metallic material, widely adopted in petrochemical industry, represent a promising alternative approach. Therefore, four types of enamel slurries were prepared by adding nano-Al₂O₃ particulates in the designed wet frit power, namely the frit powder with 0, 2, 4 and 6 mass% nano-Al₂O₃ particulates were prepared respectively, which were further ground by ball mill, subsequently applied on Al-alloy by cold spraying method and finally sintered at 550℃ to gain coatings/Al-alloy. The microstructure and surface morphology of the coatings were characterized using. Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, thermogravimetric-differential scanning calorimetry (TG-DSC), X-ray photoelectron spectroscopy (XPS), laser confocal microscopy, and scanning electron microscopy (SEM). Their corrosion behavior was comparatively examined via immersion tests in 3.5%NaCl solution whilst with electrochemical measurement. The results indicate that during the sintering process, Al₂O₃ incorporates into the silicate network by capturing non-bridging oxygen and forming [AlO₄] structural units, thereby promoting the expansion and densification of the amorphous network. Among others, the coating containing 4%Al₂O₃ exhibits the best corrosion resistance, which may be ascribed to its dense network structure that acts as an effective barrier against corrosive medium penetration, extends the diffusion path, and suppresses crack initiation and propagation.

The stress corrosion cracking behavior of Ti80 Ti-alloy in a 3.5%NaCl solution under pressures within a range from 0.1 to 15 MPa was systematically investigated using wedge-opening loading specimens, with emphasis on the influence of pressure on the SCC threshold (K_ISCC) and fracture mechanism. The results indicate that within the pressure range of 0.1-10 MPa, the K_ISCC values of Ti80 Ti-alloy in the 3.5%NaCl solution ranged between 50.36 and 53.51 MPa·m^1/2. When the pressure increased to 15 MPa, the average K_ISCC value decreased to 47.79 MPa·m^1/2, indicating the SCC susceptibility was enhanced. The fracture surfaces primarily consisted of a fatigue pre-cracked zone, SCC propagation zone, and tearing zone. The SCC zone exhibited a rough and porous morphology, characterized by typical quasi-cleavage fracture combined with local dissolution features, and the brittle characteristics intensified with the increasing pressure. Electron backscatter diffraction analysis further revealed that the crack propagation was predominantly transgranular, accompanied by local intergranular corrosion and branching phenomena. Under high pressure, the plastic zone at the crack tip was reduced, and local strain concentration became significant, indicating the activation of the hydrogen-enhanced localized plasticity mechanism. Comprehensively, the SCC of Ti80 Ti-alloy in 3.5%NaCl solution follows a combined mechanism of “anodic dissolution” and “hydrogen-induced cracking.” Hydrostatic pressure significantly increases the SCC susceptibility of the Ti-alloy by promoting Cl^- penetration and accelerating hydrogen accumulation.

Polypyrrole (PPy) particulates was deposited on the surface of aramid fibers (AF) by in-situ polymerization method to obtain PPy covered AF composite fibers (PPy/AF). Then a series of PPy/AF/EP composite coatings were then fabricated by adjusting the mass fraction of the modified fibers in the epoxy resin. The morphology and chemical structure of the composite fibers were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy. The mechanical properties and protectiveness the coatings in 3.5%NaCl solution were systematically investigated via tensile tests and electrochemical measurements. The results showed that for composite coating with modified fibers of 2.0%PPy0.5/AF, the tensile strength of the composite coating increased from 39.6 MPa to 55.68 MPa, corresponding to a 40.61% enhancement. After immersion in 3.5%NaCl solution for 168 h, the low-frequency impedance modulus (|Z|_{0.01 Hz}) of the composite coating remained at 6.3 × 10⁹ Ω·cm², which was approximately four orders of magnitude higher than that of the pure epoxy coating. The above results indicate that the incorporation of Ppy-modified aramid fibers can simultaneously enhance the mechanical properties and corrosion resistance of the epoxy coatings, demonstrating great potential for applications in the field of multifunctional protective coatings.

The influence of different applied cathodic potentials on the hydrogen embrittlement susceptibility of two Ni-Cr-Mo-V high-strength alloy steels (steel A and steel B) in artificial seawater was investigated by means of electrochemical measurement, slow strain rate tensile testing, fracture morphology observation, and hydrogen concentration measurement. The results indicate that the potential at which steel A undergoes only the hydrogen evolution reaction in artificial seawater is -1000 mV, while that of steel B is -880 mV. Moreover, as the cathodic potential shifts to more negative values, the hydrogen embrittlement susceptibility of both steels increases significantly. Although by applied potential -750 mV, the two steels all locate in low-risk zone of fracture, in contrast, by potential -850 mV, the steel B locates in zone of brittle fracture occurrence, while the steel A locates in high-risk zone. By applied potential -950 mV and below, the two steels locate all in embrittlement fracture zone. This may be attributed to that a large number of dislocations in steel B can enhance the diffusion of hydrogen atoms inwards the steel substrate, and the lath-like grain boundary structure can absorb more hydrogen rather than the granular grain boundary of steel A, thus the steel B shows higher sensitivity to hydrogen embrittlement.

In order to address the issue that the steel used in mining engineering in mining areas around the country is prone to failure due to corrosion caused by the high mineral containing mine waters with varying pH values. Herein, the corrosion behavior of 23MnNiMoCr54 steel in artificial high-mineralized mine waters with pH values of 5, 8, and 9 respectively was studied by means of immersion test, thickness loss measurement, X-ray diffraction, scanning electron microscopy, and electrochemical tests etc in terms of the surface morphology, composition of corrosion products and evolution of electrochemical behavior of the steel. The corrosive medium selected was an artificial mineralized water with a mineralization degree of 10 g/L as precursor, then based on the actual situation of underground waters in typical mining areas around the country, three homogeneous but with different pH values (pH = 5, 8, and 9) of artificial mineralized waters were prepared. Results show that after immersion in the three high-mineralized mine waters respectively, the corrosion products of the steel were mainly composed of α-FeOOH, γ-FeOOH, β-FeOOH, and Fe₃O₄. Additionally, CaCO₃ and Mg(OH)₂ were generated in neutral and weakly alkaline waters, while a higher content of calcium/magnesium-containing products may form in the weakly alkaline water. The corrosion kinetic characteristics followed the trend of "initial increase in corrosion rate, subsequent decrease in the middle stage, and stabilization in the late stage". In acidic high-mineralized mine water, the corrosion rate was consistently higher than that in neutral and weakly alkaline waters due to the incomplete and easily soluble products scale. In the weakly alkaline water, Fe₃O₄ synergistically formed a compact products scale with CaCO₃ and Mg(OH)₂, exhibiting the optimal corrosion inhibition effect, while the corrosion rate in the neutral water was intermediate between the other two. High-mineralized mine water exerted dual effects: on one hand, high concentrations of Cl^- and SO{}_{\mathrm{4}}^{\mathrm{2}-} accelerated matrix dissolution and product scale damage; on the other hand, it induced the enrichment of CaCO₃ and Mg(OH)₂ on the outer portion of rust scale in neutral and weakly alkaline waters, indirectly promoting the formation of a composite protective produts scale. The corrosive effect of aggressive ions (Cl^-, SO{}_{\mathrm{4}}^{\mathrm{2}-}) in high-mineralized mine water and the pH-dependent structural evolution of the products scales are the core factors affecting the corrosion failure of the steel. The weakly alkaline water is conducive to the formation of a stable protective scale, whereas the acidic water may accelerate the corrosion failure. This study provides a scientific basis for the corrosion protection design for steels such as 23MnNiMoCr54 steel used in mining areas with different pH characteristics.

To meet the service requirements of ocean engineering equipment in complex conditions of temperature fluctuations and harsh corrosive environments, herein, high entropy alloy (HEA) coatings of AlCoCrFeNi and AlCoCrFeNiY_0.5Hf_0.4 were prepared on AH40 marine steel. The corrosion behavior of these coatings in 3.5% (mass fraction) NaCl solution over the temperature range of 0-60 ℃ was systematically investigated by means of potentiodynamic polarization, electrochemical impedance spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy, in terms of the electrochemical characteristics, passivation film structure, corrosion morphology, and corrosion products of the coatings. The results indicate that at lower temperatures, the AlCoCrFeNiY_0.5Hf_0.4 coating exhibits excellent corrosion resistance, especially at 0 and 20 ℃, with high charge transfer impedance and stable passivation behavior. As the temperature increases, the corrosion resistance of the coating significantly deteriorates, as evidenced by an increase in corrosion current density, unstable passivation film, and the formation of local corrosion pits. The corrosion resistance of AlCoCrFeNiY_0.5Hf_0.4 coating at higher temperatures is significantly better than that of AlCoCrFeNi coating, which is related to the promotion effect of Y and Hf on the formation a more stable and dense passivation film on the coating surface. The increase in temperature has a profound impact on the electrochemical stability and corrosion mechanism of coatings, especially at high temperatures, which challenges the stability of passivation films and accelerates the corrosion rate. The results provide a meaningful reference for the design and optimization of new adaptive marine anti-corrosion coatings, and have important application prospects.

Mg-alloys have broad application prospects in fields such as aerospace and automotive manufacturing due to their lightweight and high-strength characteristics. However, their poor corrosion resistance limits their widespread application. This study aims to systematically investigate the effect of different Al contents on the microstructure and corrosion behavior of Mg-xAl-Zn (x = 3, 6, 8) alloys. Alloys with varying Al contents were prepared by extrusion, and their microstructures and phase compositions were analyzed using Scanning Electron Microscope (SEM) and X-ray Diffractometer(XRD). The corrosion behavior of the alloys in 3.5%NaCl solution was evaluated through electrochemical tests, hydrogen evolution measurements, and mass loss analysis. Increasing the Al content facilitates the precipitation of the β-Al₁₂Mg₁₇ phase, and the morphology and distribution of this intermetallic compound significantly affect the corrosion properties of the alloys. During corrosion, the β-Al₁₂Mg₁₇ phase acts as a cathodic site, thereby accelerating the corrosion of the Mg-matrix. In general, a larger cathode-to-anode area ratio results in a higher galvanic corrosion rate. A compact surface film formed during the corrosion process of an alloy can provide certain degree of protective effect, thereby improving its corrosion resistance. It follows that as the Al content increases, the corrosion resistance of the alloy first improves and then decreases, among others, the AZ61 (Mg-6Al-Zn) alloy exhibits the best corrosion resistance.

The corrosion behavior of laser additively manufactured 316L (LMD-316L) stainless steel in 3.5% (mass fraction) NaCl solution at temperatures within a range 25-65 ℃ was investigated. Electrochemical test results show that the breakdown potential, free-corrosion potential, and capacitive arc radius of LMD-316L stainless steel decrease progressively with the increasing temperature. Re-passivation capability of the LMD-316L steel is better at 55 and 65 ℃ than those at other temperatures. Nevertheless, LMD-316L stainless steel exhibits poorer corrosion resistance than the conventionally forged 316L stainless steel. Microstructural characterization results indicate that the cellular structure, high-density dislocation, and spherical nano- oxide inclusions were formed in the LMD-316L stainless steel. The differences in corrosion potentials are detected in between the cell interiors, cell walls, and nano-oxides. The cell walls, enriched in alloying elements, display a higher potential, while the cell interiors exhibit the lowest potential, which induces micro-galvanic coupling and leads to preferential pitting initiation at the interfaces between cell walls and cell interiors. The results provide guidance and supporting data for the engineering application of additively manufactured 316L stainless steel.

The crevice corrosion behavior of 316LN stainless steel heating tubes used in pressurized water reactor (PWR) pressurizers was assessed in simulated overheating conditions of electric heater. Therefore, a high-temperature and high-pressure crevice corrosion apparatus was designed, in which crevice and non-crevice 316LN stainless steel specimens were exposed for 50, 100, 250 and 500 h, respectively. The results indicate that corrosion products formed on both crevice and non-crevice specimens exhibit a duplex-layered structure. The inner layer consists of nanocrystalline Cr₂O₃ and FeCr₂O₄ phases, while the outer layer is composed of polyhedral Fe₃O₄ particles. Statistical analysis of corrosion product thickness shows that the corrosion product scales on crevice specimens are significantly thicker than those on non-crevice specimens, accompanied by pronounced enrichment of Fe ions within the crevice regions, indicating aggravated corrosion in crevice conditions. Furthermore, the thickness of corrosion product scales on these two types of specimens is influenced by exposure time in overheating conditions. Prolonged overheating affects both the formation and dissolution processes of the corrosion product films. For crevice specimens, the oxide scale thickness increases rapidly within the initial 50 h and then grows slowly during the 100-500 h exposure period, whereas the thickness of corrosion products scale on non-crevice specimens exhibits a slight decreasing trend with time.

The chemical Ni-P coating has been widely used in corrosion protection of marine engineering equipment due to its excellent corrosion resistance and wear resistance. However, when traditional chemical plating is adopted to prepare Ni-P coating for the B30 Cu-Ni alloy tubes, which are commonly used for marine equipment cooling systems, the quality of the Ni-P coating is easily affected by ion “depletion” and difficulty in removing bubbles inside the tube. Flowing chemical plating is expected to solve this problem. However, the flow velocity of the chemical plating solution may be the key factor affecting the performance of the resulting Ni-P coating, so it is of great significance to clarify the optimal flow velocity of the chemical plating solution for obtaining high-performance Ni-P coatings. Hence, the chemical plating Ni-P coating was plated on the inner wall surface of B30 Cu-Ni alloy tube via a home-made electroless plating set for tubes with by varying the flowing rates of a designed plating solution. Then, the acquired coatings were characterized by means of erosion-corrosion test, electrochemical tests and surface morphology analysis etc., in terms of the effect of the flowing rates of plating solution on the quality of the plated coatings The results show that the flowing rate of chemical plating solution affects the surface morphology, deposition rate, and erosion-corrosion resistance of the Ni-P coating, but has few effects on the composition, hardness, and crystal structure of the coating. Compared to the bare B30 Cu-Ni alloy, the Ni-P coatings obtained under different flow rates of the plating solution all demonstrate superior erosion-corrosion resistance, among others the coating prepared with the chemical plating solution with flowing rate of 1.6 L/min exhibits the highest resistance to erosion-corrosion.

The corrosion behavior of Q235 carbon steel in a simulated saline soil of Southern Xinjiang was investigated by means of macroscopic morphology observation, mass loss measurement, and electrochemical measurement, as well as microscopy, scanning electron microscope (SEM), energy dispersive spectrometer (EDS), and X-ray diffraction (XRD). The results indicate that the apparent corrosion morphology of Q235 carbon steel is primarily characterized by pitting corrosion, localized corrosion, uniform corrosion, and layered exfoliation, with an average corrosion rate of 96.8 mg/(cm²·a). The corrosion products mainly consist of α-FeOOH, Fe₃O₄, and Fe₂O₃, with numerous microcracks and structural defects present within the product scale. During the corrosion process, the protective property of the surface product scale weakens. The Faraday impedance (polarization resistance, R_p) of the circuit at zero angular frequency (\omega = 0) gradually decreases, accompanied by a reduction in charge transfer resistance. This is one of the main reasons for the accelerated corrosion rate of Q235 carbon steel.

Cu has excellent electrical conductivity and corrosion resistance and is one of the ideal materials for grounding electrodes. Herein, the corrosion behavior of Cu was assessed in artificial solutions, simulating the leaching solution of the soil at Korla district of Xinjiang with different Cl^- content namely 0.05%, 0.5%, 1.0%, and 2.0% in mass fraction, was studied via immersion test for 28 d and electrochemical measurement etc. The surface morphology, corrosion products, and corrosion rate of Cu were then characterized after the immersion test. The results show that in solutions with low chloride-content (≤ 0.5%), the Cu surface exhibits relatively mild corrosion degree with slight corrosion products and relatively small amount of corrosion pits, which corresponds to better corrosion resistance. Contrast, in solutions with high Cl^--content (≥ 1.0%), the surface corrosion of Cu is relatively severe with significant corrosion products and much more corrosion pits. Taking the corrosion rates of Cu in solutions with different Cl^--content, the corrosiveness of solutions may be ranked as the following order: 2.0% > 1.0% > 0.5% > 0.05%. In terms of corrosion products, for the solutions with 0.05%, 0.5% and 1.0%Cl^-, the formed corrosion products compose mainly of Cu₂O and CuO; While for the solution with 2.0%Cl^-, the corrosion products compose mainly of Cu₂O, CuO, and Cu₂(OH)₂CO₃. As the Cl^--content increases, the corrosion rate rises and more corrosion products form. When the Cl^--content reaches 2.0%, the Cu may immerse in a strongly corrosive medium for a long time and react with CO₂ in the solution, thus gradually generate a less protective greenish basic copper carbonate on the Cu surface, by which the corrosion may be intensified. Electrochemical analysis also indicates that, as the Cl^--content increases, the capacitive arc radius as well as R_ct (Charge transfer resistance) decreases, the corrosion current density increases, therewith the Cu corrosion becomes more severe.

Corrosion fatigue data are the basis for fatigue design, operation, and life assessment of nuclear power plants. Based on the corrosion fatigue data of stainless steel weld seam in air and high-temperature pressurized-water, the mean curve of fatigue life in the form of the Langer equation was established. The effect of strain rate and water temperature on the corrosion fatigue life of stainless steel weld seaam was analyzed, whilst, the environmentally assisted fatigue effect was considered in the fatigue model. Then a design fatigue model for stainless steel weld seam that considers strain rate and water temperature was established.

The hydrogen diffusion behavior in X65 pipeline steel during simultaneously tensile deformation testing and hydrogen permeating for the test sample was assessed via a setup of combined a dual-electrochemical cell and a stress corrosion testing machine. While the effect of strain rate and stress concentration on the hydrogen diffusion was examined respectively. The results indicate that the influence of tensile deformation on hydrogen diffusion is dependent on the applied strain rate. Plastic deformation at high strain rates significantly inhibits hydrogen diffusion, whereas at low strain rates, the restraining effect of the plastic deformation on hydrogen atoms is weakened. Stress concentration at the notch during tensile deformation drives the accumulation of hydrogen atoms toward the high-stress region. The synergistic effect of this accumulation and the plastic deformation at the notch, may further enhance the hydrogen trapping, thereby accelerating the process of hydrogen-induced damage. The magnitude of this notch trapping effect strengthens with the increasing stress concentration. In contrast, regions with minimal stress concentration, such as non-notched areas, exhibit a comparatively minor influence on the hydrogen permeation process.

The initial failure process of the powder spraying coating (namely 60% polyester, 10% TiO₂, 7% curing agent, 6% leveling agent, 2% pigment, 15% auxiliary materials), which was applied on 316 stainless steels, in artificial coastal atmosphere and seawater was investigated by electrochemical impedance spectroscopy (EIS) technique, whilst the failure process was analyzed. The results showed that in the artificial coastal atmosphere, the coating resistance decreased from an initial value of 1.07 × 10⁸ Ω·cm² to 1.48 × 10⁶ Ω·cm² over the first 96 hours by a descent rate of 1.10 × 10⁶ Ω·h^-1. In the artificial seawater, the coating resistance decreased from an initial value of 1.56 × 10⁸ Ω·cm² to 1.99 × 10⁶ Ω·cm² over the first 48 hours by a descent rate of 1.30 × 10⁶ Ω·h^-1. Whether the coated steels expose in the artificial coastal atmospheric environment or immerse in the artificial seawater, the lnC_c-t^1/2 curves for coatings indicated that the coating capacitance presented two typical stages as the corrosion time increased, the coating capacitance increased rapidly in the beginning time of corrosion, and then tented to be a slow growth. Furthermore, the water molecular diffusion coefficient D for the powder spraying coating in the artificial coastal atmosphere was 1.69 × 10^-11 cm²·s^-1, while that was 2.31 × 10^-11 cm²·s^-1 in the artificial seawater, which is slightly higher than that in the coastal atmosphere.

The gathering pipelines of a gas field in the Northwestern region suffered from severe corrosion risk, hence a comprehensive technical countermeasure was then postulated covering the identification of corrosion factors, the prediction of corrosion-rate, and the optimization of prevention strategies. Herein, the corrosion behavior of the gathering pipeline steel was assessed via a simulation set of the corrosive environment for the pipelines of the gas field in this region, as well as an orthogonal experimental arrangement combined with the entropy-weight rank-sum ratio method. It was revealed that the CO₂ partial pressure, the chloride concentration, and the SRB activity were the main controlling factors for uniform corrosion and local corrosion, but the influence weights of these factors on the two types of corrosion were different. Further, a modified De Waard95 CO₂ corrosion model was developed by introducing correction terms for Cl^- concentration and microbial activity, which significantly improved the corrosion-rate prediction accuracy and achieved a determination coefficient (R²) of 80.98%. Considering the main corrosion factors in the gas field, an OED/BKC composite inhibiting biocide system was developed. In the simulated conditions, the corresponding inhibition rate for uniform corrosion reached 94.25% and that for pitting corrosion was 90.74% at optimal concentrations of 150 mg/L OED and 50 mg/L BKC, with nearly 100% effectiveness for sterilization. The proposed methodology provides a reliable technical basis for corrosion warning and prevention in this gas field.