The low-cycle fatigue behavior of T91 steel hollow specimens filled with oxygen-saturated liquid lead-bismuth eutectic (LBE) was investigated at different strain rates (0.0008-0.4 % s(-1)) under a strain amplitude of 0.6 % at 350 degrees C. The fatigue life remained comparable at strain rates ranging from 0.4 % s(-1) to 0.01 % s(-1), slightly decreased at 0.004 % s(-1), but increased at 0.0008 % s(-1). The fatigue crack initiated at the inner surface and propagated to the outer surface at 0.4 similar to 0.004 % s(-1), it reversed at 0.0008 % s(-1). Liquid metal embrittlement characterized by quasi-cleavage cracking occurred at 0.4 similar to 0.004 % s(-1). Oxidation inhibited the propagation of short cracks (<65 mu m) on the inner surface at 0.0008 % s(-1). The fatigue crack initiation and propagation mechanisms at different strain rates are discussed.

Creep-fatigue (C–F) interaction is a critical failure mode for structural components of lead–bismuth eutectic (LBE)–cooled fast reactors. However, the degradation mechanisms of candidate materials like T91 steel under the synergistic effects of C–F loading and liquid LBE remain poorly understood. In this study, the effect of hold time on the C–F behavior of T91 steel was investigated in oxygen-saturated LBE at 550 °C. The results show that the failure life decreases with increasing hold time from 0 to 2000 s at a strain rate of 0.04%s⁻¹ . Longer hold times enhance C–F interaction, thereby accelerating oxidation-assisted corrosion and promoting LBE penetration along grain boundaries (GBs). As intergranular corrosion damage progressively dominates and the solid–liquid interface deteriorates, the fracture mode transitions from quasi–brittle to brittle cracking. Notably, the coupled C-F-oxidation process significantly accelerates Cr diffusion, promotes the formation of spinel oxides and causes Cr depletion along the GB network near the oxidation front. These microstructural and chemical changes induce widespread intergranular cracking and the formation of defect zones containing cracks and voids. The induced crack network and associated defects further increase the oxidation–corrosion rate, trigger oxide–scale spallation, and enable liquid LBE to preferentially wet and penetrate along high–angle GBs near the crack tip. Consequently, these synergistic processes severely degrade the intergranular corrosion resistance and near–surface integrity of T91 steel, leading to a substantial reduction in its effective load-bearing area. Based on these findings, a synergistic degradation mechanism is proposed, in which C–F–driven oxidation and LBE–enhanced embrittlement jointly sustain intergranular cracking progression.

Corrosion fatigue is a typical failure mode of metallic materials subjected to the combined effects of cyclic loading and corrosive environments.It is widely observed in critical fields such as nuclear power,marine engineering,aerospace,and energy equipment,and directly affects the service safety and life assessment of engineering components.With the advancement of advanced energy systems operat-ing in extreme environments such as deep space,deep sea,and deep earth,materials increasingly experi-ence severe environmental-mechanical coupling damage.Among these environments,high-temperature pressurized water,liquid lead-bismuth,and marine conditions represent typical corrosive systems.There-fore,understanding and predicting the corrosion fatigue behavior of metallic materials under these condi-tions is of considerable importance.This paper reviews recent research progress on corrosion fatigue ex-perimental techniques,damage mechanisms,and prediction models for metallic materials in the three representative corrosive environments mentioned above.Regarding experimental techniques,particular attention is given to the development of fatigue testing devices capable of simulating service environ-ments,as well as in situ monitoring methods for specimen strain/displacement and crack length.In terms of damage mechanisms,the competition and synergistic interactions among several mechanisms are dis-cussed,including stress concentration at corrosion pits,rupture of protective films and slip dissolution,hy-drogen ingress and hydrogen-induced damage,and reductions in surface energy.For prediction models,the evolution from traditional empirical models,such as the Basquin and Coffin-Manson models,to data-driven machine learning approaches is summarized.The limitations of current models in terms of engi-neering applicability and integration of physical mechanisms are also highlighted.Furthermore,this paper discusses major challenges in the field,including the lack of experimental techniques for emerging ex-treme environments,insufficient understanding of multimechanism coupled damage theories,and the ab-sence of high-precision life prediction models under small-sample conditions.Future research directions are proposed,including the development of cross-scale in situ characterization techniques,the integra-tion of physical mechanisms with machine learning methods,and the advancement of design and evalua-tion systems for materials resistant to corrosion fatigue.

For hydrogen-blended natural gas pipelines, trace O2 and CO inevitably exist as impurity gases and affect the interaction between hydrogen and pipeline materials, thereby altering hydrogen embrittlement (HE). In this study, gaseous hydrogen permeation and slow strain rate tensile (SSRT) tests were conducted to quantitatively compare the effects of O2 and CO on the HE of X42 pipeline steel dominated by body-centered cubic (bcc) α-Fe within the 0–100 vppm range. Combined with fracture surface and cross-section characterization of post-fracture specimens, the hydrogen-induced failure mechanism was clarified. Experimental results demonstrate that O2 has a stronger inhibitory effect on HE than CO at equivalent contents. As the blending content increases, the inhibition is continuously enhanced with a gradually weakening enhancement trend. Fracture characteristic analysis results indicate that the increase of tensile-directional grain length and average kernel average misorientation (KAM) value in the gas-side region after O2 or CO blending verifies the mitigated HE. Furthermore, O2 or CO blending mitigates the impacts induced by the synergistic action of the hydrogen-enhanced localized plasticity (HELP) and hydrogen-enhanced decohesion (HEDE) mechanisms on the tensile fracture behavior of the material. The density functional theory (DFT) calculation results show that pre-adsorbed O atoms or CO molecules on the Fe(110) surface increase the energy required for hydrogen dissociation, adsorption and diffusion. In particular, O atoms induce a greater energy increment, leading to stronger suppression of hydrogen permeation.

The corrosion behavior of a low‑carbon steel and five low‑alloy steels (with Mn, Cr, or Mn–Cr additions) in brackish water was investigated using experimental and thermodynamic calculation methods. In Mn–Cr steels (Steel 4# 0.5Cr‑0.5Mn and Steel 6# 2.4Cr‑0.5Mn), the corrosion products from the inner to the outer rust layer follow the sequence FeCr₂O₄, Cr₂O₃, MnCr₂O₄, and MnFe₂O₄. FeCr₂O₄ and Cr₂O₃ promote the nucleation and growth of α‑FeOOH in the inner rust layer, thereby enhancing corrosion resistance. In contrast, MnCr₂O₄ hinders α‑FeOOH formation and weakens protection. As a result, the corrosion resistance of Mn–Cr steels is superior to that of Mn‑only steel (Steels 2# 0.5Mn) but inferior to that of Cr‑only steels (Steel 3# 0.5Cr and  Steel 5# 2.4Cr). This confirms a clear interactive effect between Mn and Cr: Mn preferentially dissolves and accelerates initial corrosion, later forming MnFe₂O₄ that inhibits corrosion, whereas Cr immediately forms protective FeCr₂O₄/Cr₂O₃ films that suppress corrosion throughout immersion. The opposing effects of Mn and Cr in combination lead to intermediate performance, directly demonstrating their interaction in governing the corrosion resistance of low‑alloy steels.

Alumina-forming austenitic (AFA) steel, as one candidate structural material for lead-cooled fast reactors, has not been systematically studied in terms of mechanical behaviors in liquid lead-bismuth eutectic (LBE) environments. This paper investigated the low-cycle fatigue properties of AFA steel at 500 degrees C in oxygen-saturated LBE at various strain rates. The results show that fatigue life of AFA steel at a strain amplitude of 0.6 % is reduced by approximately 60 % as the strain rate is reduced from 0.3%/s to 0.003%/s. The fatigue fracture surface of AFA steel was characterized by ductile cracking with fatigue striation at 0.3 %/s, while embrittlement characterized by intergranular cracking and quasi-cleavage cracking was observed at 0.003 %/s. The fatigue cracks mainly initiated at slip bands at 0.3 %/s, but at grain boundary at 0.003 %/s. Intergranular oxidation promotes the crack initiation at the grain boundaries under cycle loading in fatigue tests. The preferential intergranular oxidation and subsequent Pb-Bi penetration along grain boundaries promoted the intergranular cracking at 0.003 %/s. The related fatigue crack growth mechanisms of AFA steel within liquid LBE were discussed.

The durability of overpacks used for geological disposal of high-level radioactive waste largely depends on the corrosion resistance of their manufacturing materials. The corrosion evolution behavior and corrosion kinetics of Q235 carbon steel and NiCu low alloy steels (1Ni and 3Ni) in compacted bentonite infiltrated by simulated deoxygenated Beishan groundwater were investigated using corrosion weight loss method, electrochemical tests, and several characterization techniques. Initially, the cathodic corrosion process transformed from the reduction of residual oxygen to the combined reduction of oxygen and rust, while the anodic process primarily involved the active dissolution of Fe. For Q235 steel, the Fe(II)-containing corrosion products were easily oxidized to Fe(III)-containing ones by residual oxygen, which promoted rust reduction. However, in the corrosion products of NiCu steels, the isomorphous substitution of Fe(II) in Fe6(OH)12CO3 by Ni(II) enhanced the compound's oxidation resistance and reduced the formation of Fe(III) corrosion products, thereby inhibiting the early-stage cathodic process. Over time, oxygen was gradually consumed and the cathodic process shifted to hydrogen evolution reaction (HER) and rust reduction. Subsequently, Fe(III) corrosion products were depleted due to continuous reduction, after which the cathodic process became controlled by HER. Following long-term embedment, both the cathodic and anodic polarization resistances of NiCu steels were significantly higher than those of Q235 steel. The role of Ni and Cu was to reduce the driving force of HER by increasing open circuit potential. Meanwhile, the formed Ni4Fe2(OH)12CO3, NiFe2O4, and CuFeO2 improved both the stability of the rust layer and its protective properties.

The corrosion products of steel overpacks for high-level radioactive waste disposal significantly affect their cathodic depolarization behavior during corrosion and may even alter the depolarization mechanism. In this study, the anodic polarization products of NiCu low alloy steel were prepared by potentiostatic polarization in compacted bentonite with 20% and 40% water contents. Combined with the chemical composition, structure of corrosion products, and corrosion kinetic parameters, the influence mechanism of different anodic polarization products on the corrosion behavior of steel at open circuit potential was revealed. The results showed that the products formed under weak anodic polarization potentials were mainly Fe6(OH)12CO3 and Fe6(OH)12SO4. With rising polarization potential, Fe3O4, alpha-FeOOH, and Fe2O3 & centerdot;H2O emerged with increasing relative contents. Meanwhile, the residual Fe3C also accumulated in products. At open circuit potential, alpha-FeOOH, Fe2O3 & centerdot;H2O and Fe3C from strong polarization showed stronger cathodic depolarization and micro-galvanic effects than weak polarization-derived green rust, inducing a sharp drop in the cathodic and anodic polarization resistances of steel. Additionally, products formed in the 20% water content system at weak polarization resulted in lower polarization resistances than the 40% system, whereas the opposite trend occurred under strong polarization. The former was due to more abundant and easily diffused oxygen in unsaturated bentonite's capillary pores, which oxidized green rust to alpha-FeOOH/Fe2O3 & centerdot;H2O and enhanced cathodic depolarization capacity. The latter was attributed to the loose and porous corrosion products formed under strong polarization potential when the water was sufficient, which decreased the inhibition on steel anodic dissolution.

The contradiction between mechanical properties and corrosion resistance in low-carbon ship plate steel poses a significant challenge for material design, particularly in cargo oil tank (COT) environments. In this study, a deformation spheroidization treatment (DST) is proposed to simultaneously enhance both properties of Q235 low carbon steel through microstructure optimization. The microstructures before and after DST were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electron backscatter diffraction (EBSD). Mechanical properties were evaluated by hardness and tensile tests, while corrosion behavior in a simulated COT bottom plate environment was investigated via weight loss measurements, electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, scanning Kelvin probe force microscopy (SKPFM), and corrosion morphology analysis. The results demonstrate that DST improves the ultimate tensile strength from 345 MPa to 402 MPa (+16.5%), the yield strength from 223 MPa to 246 MPa (+10.3%), while maintaining a high elongation of 28%. Meanwhile, the corrosion rate after 216 h of immersion decreases from 6.06 mm/a to 4.62 mm/a (−23.8%). The enhanced strength and ductility are attributed to fine-grain strengthening, dislocation strengthening, and dispersion strengthening. The transformation of lamellar cementite into dispersed fine-grained cementite mitigates the acceleration effect of micro-galvanic couples and promotes uniform corrosion. Through microstructure regulation, this study successfully overcomes the trade-off between strength and corrosion resistance in low-carbon ship plate steel, offering a new pathway for the development of economically viable and highly durable marine steel.

As an essential alloy element in the steel industry, Mn plays an important role in improving the mechanical properties of steel. However, the effect of Mn on the corrosion resistance of steel is still unclear. In this paper, the influence of solid solution Mn on the corrosion resistance of low carbon steel in brackish water was explored by combining experiments with theoretical calculations. Chemical analysis, surface element analysis, the first-principles calculation and activation energy calculation indicate that Mn dissolves preferentially than Fe, and it first enters the solution in the form of Mn2+ leaving vacancies in the surface layer of substrate, which reduces the energy barrier of surrounding iron dissolution, promotes the dissolution of Fe and accelerates the corrosion of substrate. Subsequently, continuously enriched Mn2+ in solution partially transforms into MnFe2O4, which exists in the rust layer and promotes the formation of alpha-FeOOH. Finally, a protective rust layer forms on the steel surface, which slows down the long-term corrosion of steel. (c) 2025 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

In order to address the issues of low seam strength in nickel-based TLP joints, a new Fe-Co-Ni-Al-B multicomponent alloy filler was designed. The microstructure of the filler and the microstructure and mechanical properties of TLP joints of GH4648 and K416B using Fe7(CoNi)63Al14B16 filler were investigated. Furthermore the effects of joining parameters on the microstructure and mechanical properties of the joint were discussed. The results show that the Fe7(CoNi)63Al14B16 multi-component alloy filler exhibits a dual-phase microstructure consisting of FCC and BCC phases. Precipitated phases within the seam primarily consisted of the matrix FCC phase, BCC phase, M23B6, Cr-Mo-W boride, and gamma '-(Ni, Co)3Al precipitates on the matrix FCC phase. At a holding temperature of 1160 degrees C for 120 min, the maximum shear strength of the joint at room temperature and 900 degrees C is 705 MPa and 380 MPa, respectively. The joints exhibit mixed-mode fracture behavior, characterized by both transcrystalline and intergranular features. The maximum differences in hardness and elastic modulus between the bonding seam and the DAZ are 28.77 GPa and 0.37 GPa, respectively. The microhardness and elastic modulus values of the joint were evenly distributed. This work provides a new idea for the TLP bonding of dissimilar superalloys utilized in the manufacturing of aero-engine turbine guide.

With the rapid growth of the international crude oil shipping industry,ensuring the safety of oil tanker transportation has become a critical concern.The cargo oil tank(COT),the primary structure for storing crude oil,is particularly susceptible to corrosion,with the inner bottom plate being a key site for failure and potential oil leakage.Low-alloy corrosion-resistant steel,mandated by the International Mari-time Organization as an alternative to traditional anticorrosion coatings,faces challenges in China due to insufficient corrosion resistance,limiting its long-term applicability in COTs.Enhancing the intrinsic proper-ties of ship plate steel while minimizing costs is therefore crucial for improving its corrosion resistance and mechanical performance.In the simulated acidic Cl-environment of a COT bottom plate,a micro-galvanic couple forms between ferrite and cementite in pearlite,with ferrite acting as the anodic phase and cementite as the cathodic phase.Over time,accumulated cementite thickens on the surface,increas-ing the anode/cathode area ratio and accelerating the corrosion rate due to intensified micro-galvanic ef-fects.To mitigate this,a deformation spheroidization process was employed to refine the microstructure without additional alloying elements.By optimizing forging and heat treatment parameters,a tempered sorbitic microstructure was achieved in T8 steel.Microstructural evolution was characterized using SEM and EBSD,while mechanical properties were assessed through microhardness testing,tensile experi-ments,and fracture morphology analysis.Corrosion behavior before and after optimization was examined via mass loss tests,electrochemical analysis,and corrosion product characterization.The results indicate that spheroidization heat treatment enhances the strength,plasticity,and toughness of T8 steel through grain refinement,dislocation strengthening,and dispersion strengthening.The transformation of bulk lay-ered cementite into fine-grained cementite effectively suppresses its accumulation on the surface during corrosion,mitigating the accelerating effect of micro-galvanic corrosion.Consequently,the corrosion re-sistance of T8 steel in the simulated COT environment was significantly improved.This study demon-strates a cost-effective approach to enhancing both the mechanical properties and corrosion resistance of ship plate steel through microstructural control,offering new insights for the development of corrosion-resistant materials for cargo oil tanks.

The low cycle fatigue behavior of T91 ferritic-martensitic steel hollow specimens were investigated in air and with oxygen saturated lead-bismuth eutectic (LBE) filled at 200 similar to 450 degrees C. A clear fatigue endurance "trough" was observed with LBE-filled hollow specimens at 300 similar to 350 degrees C, while the fatigue lives in air at different temperatures are comparable. The fracture surfaces with LBE-filled at 200 similar to 350 degrees C were characterized by quasi-cleavage cracking, which indicates the occurrence of liquid metal embrittlement. By contrast, oxide scale on surface with LBE-filled at 400 similar to 450 degrees C inhibited fatigue crack initiation. The fatigue crack initiation mechanisms at different temperatures are discussed.

Buffer material and metal disposal containers are the key engineering barriers in the geological disposal of high-level radioactive waste. The durability of disposal containers largely depends on the water content in buffer material. This work focused on investigating the corrosion evolution of NiCu low alloy steel in compacted GMZ bentonite with different water contents for 270 d by using weight loss, electrochemical measurements, and various methods for analyzing corrosion products. As the water content increased from 13% to 20%, the water in the bentonite transformed from an unsaturated to a critical saturated state, and the corrosion rate of NiCu steel clearly increased. In these two systems, the oxygen could migrate to the thin liquid film on the steel surface through the air pores in the bentonite in the gas phase and undergo cathodic reduction. Meanwhile, it oxidized the ferrous hydrolysis products into ferric corrosion products and formed a rust layer, which could block the diffusion of oxygen. At that moment, the cathodic process of NiCu steel corrosion changed to rust reduction. When the water content continually increased to 30% and 40%, the compacted bentonite was in a saturation state, and the corrosion rate of NiCu steel was significantly decreased. This was because most pores among the bentonite particles were occupied by a large amount of free water, which hindered the diffusion of oxygen and inhibited its cathodic reduction. Furthermore, it restrained the oxidation of ferrous corrosion products, which greatly weakened the cathodic depolarization of rust, leading to the cathodic process being dominated by the hydrogen evolution reaction.

The corrosion fatigue behavior of 316LN SS hollow specimen was investigated in high-temperature pressurized water at different dissolved oxygen (DO) concentrations (<5-200 ppb). The fatigue life of 316LN SS significantly increased with increasing DO concentration from < 5-20 ppb, while the effect of DO on fatigue lives apparently saturated at above 20 ppb (20-200 ppb). DO plays a significant role in microstructurally small cracks rather than mechanically small cracks. The oxidation characteristic of slip bands affects the crack initiation process. The effect of DO on the fatigue crack initiation mechanism is discussed.

The aerobic-anaerobic corrosion transition of low-carbon steel under deep geological disposal conditions is critical in corrosion evaluation of disposal containers. In this work, the corrosion evolution behavior of Q345R low-carbon steel in Beishan underground water under sealed conditions has been investigated by electrochemical impedance spectroscopy (EIS), and besides the redox potential (Eh) evolution of the corrosion electrolyte has been recorded. The results indicate that the distribution of relaxation time (DRT) analysis on EIS data can well identify the oxygen reduction reaction (ORR)-related time-constant evolution. Therefore, it could be proposed that DRT analysis on EIS data combined with Eh monitoring is applicable for the aerobic-anaerobic corrosion transition investigation of low-carbon steel under electrolyte corrosion conditions.

To achieve reliable joining of K416B and GH4648. Herein, a low-melting-point Fe7(CoNi)63Cu14B16 multiprincipal element alloy filler was designed based on Thermo-Calc simulations and empirical thermodynamic parameters. The interfacial microstructure, corresponding mechanical properties, and bonding mechanism of joints bonded at 1160 degrees C for 5 min, 15 min, 30 min, 60 min, 120 min, and 240 min were investigated. The results show that the filler alloy exhibits solidus and liquidus temperatures of 1071 degrees C and 1091 degrees C, respectively. Compared to commercial filler alloys, the high entropy mixing effect of the multi-principal element alloy filler is beneficial to inhibit the precipitation of brittle phases. The FCC solid solution forms as the matrix of the bonding seam. Precipitated phases within the matrix primarily consisted of gamma + gamma' and needle-like M6(C, B) in the DAZ I, needle-like and granular M5B3 in the DAZ II, M23B6/FCC eutectic structure with minor M5B3 in the ASZ, and M3B2 in the ISZ II. Furthermore, with the extension of the bonding time, the shear strength of the bonded joints at room temperature increased first and then remained constant. When holding for short durations, both the eutectic brittle phase and M3B2 compounds formed, which would lead to stress concentration, limiting the joint mechanical performance. When holding for 120 min or longer, the eutectic brittle phase or M3B2 phases gradually disappear, and the maximum shear strength of the joint reaches 603 MPa at room temperature. This research will offer new insights into the application of multi-principal-element alloys as braze fillers for joining or repairing superalloys.

This study investigates the interaction effects of seawater temperature (0-30 degrees C), cathodic protection (-950 mVSCE), calcareous deposition (CaCO3), and tensile loading on the electrochemical corrosion, hydrogen permeation, and stress corrosion cracking (SCC) behavior of E690 steel in marine environment. The results show that under open circuit potential (OCP) condition, the anodic dissolution-driven SCC occurs due to the combined effects of anodic dissolution of Fe and tensile stress, resulting in ductile fracture. A large number of corrosion pits form at 30 degrees C, which become crack sources under load and promote SCC. The hydrogen-induced SCC occurs to E690 steel under a cathodic potential of -950 mVSCE due to hydrogen evolution and hydrogen permeation, which causes brittle fracture. Temperature has a dual impact on SCC. On the one hand, increase of temperature promotes both electrochemical reactions and hydrogen permeation rate, which aggravates SCC sensitivity. The amount of hydrogen evolution increases from 4.1 C cm(-2) at 0 degrees C to 6.2 C cm(-2) at 30 degrees C. On the other hand, a CaCO3 deposition layer is formed on steel surface at 20 degrees C and 30 degrees C, with the average thickness of 7 and 17 mu m, respectively. Its physical covering effect slows down the rate of cathodic hydrogen evolution and hydrogen permeation, which reduces SCC sensitivity. Therefore, with the increase of temperature, the SCC sensitivity presents fluctuating changes of first increasing, then decreasing, and then increasing again. E690 steel is proved to have low SCC sensitivity at low temperature of 0 degrees C.

Purpose The purpose of this paper is to optimize a suitable electrochemical method in evaluating the corrosion rate of structural materials of 20# carbon steel, P280GH carbon steel, 17-4PH stainless steel, 304 stainless steel and Alloy 690TT in high-temperature and high-pressure (HTHP) water of pressurized water reactor secondary circuit system. Design/methodology/approach Weight-loss method has been used to obtain the corrosion rate value of each structural material in simulated HTHP water. Besides, linear polarization method and weak polarization curve-based three-point method and four-point method have been compared in obtaining a sound corrosion rate value from the potentiodynamic polarization curve. Scanning electron microscopy (SEM) and atomic force microscope have been used to characterize the microstructure and corrosion morphology of each structural material. Findings Although there is deviation in gaining the corrosion rate value compared to weight-loss test, the weak polarization curve-based four-point method has been found to be a suitable electrochemical method in gaining corrosion rate value of structural materials in HTHP waters. Originality/value This paper proposes a suitable and reliable electrochemical method in gaining the corrosion rate value of structural materials in HTHP waters. The proposed weak polarization curve-based four-point method provides a timesaving and high-efficient way in corrosion rate evaluation of secondary circuit structural materials and thus has a potential application in nuclear power plants.

The surface roughness of nuclear-grade structural material shows a significant influence on its corrosion behavior under high-temperature and high-pressure (HTHP) water exposure condition in the pressurized water reactor (PWR) system. In this investigation, the surface roughness induced oxide film evolution on 304 stainless steel (SS) in simulated HTHP water has been investigated by in-situ cyclic electrochemical impedance spectroscopy (EIS) and ex-situ characterizations. The results indicate that cyclic-EIS data interpretation can well understand the surface roughness induced oxide film growth and its structures evolution on 304 SS electrodes under HTHP water condition. Besides, the 240#-sample with a much higher surface roughness has the thickest oxide film with the largest and increasing |Z|0.01 Hz value. In contrast, the polished-sample with a much lower surface roughness has the thinnest oxide film with the lowest but stabilized |Z|0.01 Hz value. A higher surface roughness facilitates the formation of a thicker oxide film but with the loose outer layer in higher thickness than the compact inner layer. Although a lower surface roughness leads to the formation of a thinner oxide film, the compact and thus corrosion resistant inner layer contributes to a relatively lower corrosion rate of 304 SS under HTHP water environment of PWR system. In addition, cyclic-EIS data interpretation indicates that the compact inner layer contributes mainly but the loose outer layer contributes less to the measured impedance on 304 SS electrodes. The surface condition of nuclear power structural materials exerts a significant influence on their corrosion behavior in high-temperature and high-pressure water. In this work, the effect of surface roughness on the corrosion behavior of 304 stainless steel (304 SS) in the simulated secondary water was investigated. The results indicate that surface roughness has minimal impact on the composition of oxide films, but it exerts a significant influence on their structural characteristics and consequently affects the corrosion behavior. Electrochemical impedance spectroscopy (EIS) measurement and transmission electron microscope (TEM) observation suggested that the 304 SS with a higher surface roughness can lead to an oxide film with heterogeneous inner oxide layer, where a porous and discontinuous Cr-rich inner oxide layer can be observed, implying its limited protective ability. Therefore, it is recommended to regulate the surface roughness of materials in PWR for effective corrosion control.