15 January 2026, Volume 59 Issue 1

    

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  Research Status and Prospects of Corrosion and Coating Protection Technology for Offshore Wind Power

  HE Xin, DING Xueqiang, SUN Shizheng, ZHANG Xin, GE Zhongyuan, HE Qingdong, CHENG Xuequn, LIU Chao

  Materials Protection. 2026, 59(1): 1-14. https://doi.org/10.16577/j.issn.1001-1560.2026.0001

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  With the continuously growing global demand for renewable energy，the pace of development and construction of offshore wind power，a crucial component in the field of clean energy，has significantly accelerated.However，the harsh operational environment of offshore wind power，which is subject to long-term erosion from factors such as high salt spray，high humidity，prolonged sunlight and microorganisms，significantly increases the corrosion risk of wind turbine structures，thereby severely reducing their service life.Therefore，corrosion and protection issues have become critical to ensuring the long-term stable operation of offshore wind power.Starting from the factors influencing corrosion in offshore wind power，this review provided a detailed discussion of the commonly used coating protection technologies for offshore wind power surfaces.It also offered an outlook on the future development of new eco-friendly coating materials with more comprehensive corrosion resistance performance.
  
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  Research Progress on Interference and Protection of Grounding Electrodes of HVDC Transmission on Buried Pipeline

  GAO Jie, TIAN Haizhou, LI Shaofei, LIU Tianhui, GUO Xiaodong, AN Bing, LU Tao

  Materials Protection. 2026, 59(1): 15-25. https://doi.org/10.16577/j.issn.1001-1560.2026.0002

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  With the increasing number of high voltage direct current(HVDC) transmission projects in China，the issue of interference from HVDC system grounding electrodes on buried metal pipelines has become increasingly prominent.In order to conduct accurate research and analysis as well as protection assessment for the interference issue，this paper surveyed the research methodologies and influencing factors associated with HVDC system interference in recent years.The interference and corrosion patterns on pipelines were analyzed from four aspects: on-site field tests，laboratory simulation experiments，numerical simulation techniques and influencing factors.Meanwhile，the stray current protection technologies currently commonly used in HVDC systems in China were summarized，and their advantages，disadvantages and applicable scopes were elaborated.Finally，the research directions of stray current interference and protection were prospected.
  
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  Research Progress of Cu-Containing Antibacterial Oil Casing Steel for Microbial Corrosion Control

  LIU Zixuan, JIA Lihui, GAO Yunzhe, ZHAO Linlin, WANG Jiaojiao, LIU Yuejiao

  Materials Protection. 2026, 59(1): 26-38. https://doi.org/10.16577/j.issn.1001-1560.2026.0003

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  Microbial corrosion currently poses a serious threat to the safety of oil and gas extraction，and traditional protection technologies for oil casings are associated with certain environmental risks and high costs.Cu-containing antibacterial oil casing steel，designed through alloying，achieves long-lasting antibacterial performance by leveraging the multiple mechanisms of nano ε-Cu precipitates(such as cell membrane disruption，enzyme activity inhibition and DNA oxidative damage)，thereby offering an innovative approach to addressing microbial corrosion.The corrosion mechanisms of bacteria such as sulfate-reducing bacteria，iron-oxidizing bacteria and saprophytic bacteria were analyzed，and the antibacterial mechanism of Cu in Cu-containing antibacterial oil casing steel was described.The antibacterial performance primarily originated from the sustained release of Cu2＋from the nano ε-Cu phase and its multiple interaction mechanisms with microorganisms.Additionally，the influence of alloying elements on the corrosion resistance of Cu-containing antibacterial oil casing steel was summarized，and it was highlighted that the proper combination and content control of antibacterial and corrosion-resistant elements were crucial for enhancing the corrosion resistance of antibacterial oil casing steels.Moreover，the design concept and multi-scale regulation strategy of Cu-containing antibacterial oil casing steel were proposed，aiming to achieve synergistic optimization of antibacterial performance and mechanical properties.Furthermore，the hydrogen-induced cracking resistance of Cu-containing antibacterial oil casing steel was clarified，which was attributed to hydrogen permeation inhibition by CuS/FeS composite films and hydrogen trapping by nano ε-Cu precipitates.Besides，the research bottlenecks of Cu-containing antibacterial oil casing steel were summarized，including welding performance，copper-induced embrittlement and long-term antibacterial degradation.Future development directions were proposed，which should focus on composition optimization，process optimization，surface modification and green intelligent technologies，with the aim of providing guidance for the application of microbial-corrosion-resistant oil casing steels in the oil and gas industry.
  
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  Corrosion Inhibition Properties of Alginate Capsule Coated Heat-Stable Corrosion Inhibitor in High Temperature Oilfield Solution

  HE Ziqi, MA Xiumin, HOU Baorong

  Materials Protection. 2026, 59(1): 39-54. https://doi.org/10.16577/j.issn.1001-1560.2026.0004

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  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.
  
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  Effects of Adding Lignin on the Performance of Lithium-Based Grease

  SUN Shuang, SUN Yuchen, WANG Xingwei, ZHANG Chaoyang, CAI Meirong, YU Bo

  Materials Protection. 2026, 59(1): 55-61. https://doi.org/10.16577/j.issn.1001-1560.2026.0005

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  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.
  
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  Effect of Ni Addition on the Microstructure and Corrosion Resistance of Fe20Cr8Si Alloy

  SONG Chunyan, ZHANG Yu, LONG Haiyang, GUI Yongliang, MA Zhanshan, JIANG Dehua

  Materials Protection. 2026, 59(1): 62-72. https://doi.org/10.16577/j.issn.1001-1560.2026.0006

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  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.
  
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  Corrosion Behavior of Supersonic Sprayed WC Coatings on 2A12 Aluminum Alloy Surfaces under High Temperature，Strong Alkali and High Salt Environments

  TIAN Xiaoyong, LI Xiulan, ZHANG Jinghua, JIANG Benqiang, DONG Zhaopeng

  Materials Protection. 2026, 59(1): 73-83. https://doi.org/10.16577/j.issn.1001-1560.2026.0007

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  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.
  
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  Effect of Neutral Salt Spray Corrosion on the Tribological Performance of MoS₂ Coatings for Bolts

  ZHANG Qinying, YIN Xiaojian, GAO Xuemin, MA Jianhua, FENG Derong, WANG Yamei, MING Quanyuan, WAN Qiang

  Materials Protection. 2026, 59(1): 84-94. https://doi.org/10.16577/j.issn.1001-1560.2026.0008

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  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.
  
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  Corrosion Behavior of Q355B Steel in Typical Soil Environments of Wuhan and Korla

  ZHOU Qingjun, LI Yulin, SONG Fengming, CHEN Zhijian, ZHOU Xuejie

  Materials Protection. 2026, 59(1): 95-101. https://doi.org/10.16577/j.issn.1001-1560.2026.0009

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  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.
  
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  Effects of WC and TiB₂ on the Microstructure and Properties of NiCr-Based Alloys

  ZHANG Yongsheng, FU Tingfeng, YANG Wei, NI Junjie, HUANG Zhiquan, LIU Shengxin

  Materials Protection. 2026, 59(1): 102-109. https://doi.org/10.16577/j.issn.1001-1560.2026.0010

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  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.
  
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  Effect of Post-Treatment Methods of Polyaniline Microcapsules on the Protective Performance of Epoxy Coatings

  FENG Yu, ZHANG Yingjun, LOU Sangang, LI Mengyang, JIANG Yong, YE Lunjun

  Materials Protection. 2026, 59(1): 110-118. https://doi.org/10.16577/j.issn.1001-1560.2026.0011

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  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.
  
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  Effect of Linear Velocity on the Properties of Multicomponent Zinc Alloy Diffusion Layers in a Mechanically Assisted Diffusion Process

  AI Junjie

  Materials Protection. 2026, 59(1): 119-127. https://doi.org/10.16577/j.issn.1001-1560.2026.0012

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  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.
  
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  Corrosion Performance Analysis and Evaluation of Downhole Dissolvable Staged Fracturing Aluminum-Based Alloy Tools

  LIU Junyan, ZHOU Jin, LI Lili, WANG Qiao, WANG Kun, WANG Lang

  Materials Protection. 2026, 59(1): 128-135. https://doi.org/10.16577/j.issn.1001-1560.2026.0013

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   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.
  
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  Stress Corrosion Cracking Failure Analysis and Countermeasures for Preheater Joints in Bayer Liquor Environments

  LI Yongjun, LI Zhigang, FENG Zongjian, MO Qianci, WEI Yuwei, LAN Jiahong

  Materials Protection. 2026, 59(1): 136-144. https://doi.org/10.16577/j.issn.1001-1560.2026.0014

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  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.
  
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  Corrosion Behavior for Sealing Polymer Materials under Simulated Condition for High-Pressure Proton Exchange Membrane Water Electrolysis

  PENG Heng, DONG Minghui, ZHANG Maoqi, BAI Mingxian, GUO Jianwei

  Materials Protection. 2026, 59(1): 145-152. https://doi.org/10.16577/j.issn.1001-1560.2026.0015

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  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.
  
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  Failure Analysis of Corrosion-Induced Perforation in J55 Tubing and Investigation of the Corrosion Mechanism

  ZHAO Jun, ZHENG Dongwei, ZHOU Zhisuo

  Materials Protection. 2026, 59(1): 153-158. https://doi.org/10.16577/j.issn.1001-1560.2026.0016

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  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.