Mg-alloy is the lightest engineering metal material, and its dissolution characteristics, corrosion mechanism and protective measures have been widely studied. Corrosion test methods and techniques for Mg-alloys have been critically important to the research. Due to the negative difference effect, the testing techniques and analysis methods of Mg-alloys are different from those of other metals. This paper reviews the research progress of corrosion test methods and techniques for Mg-alloys, including the general and characteristic test technologies, analyzes the applicable conditions and application cases of various testing technologies, and focuses on the comparison of corrosion rate testing methods. It is expected that the review will provide a solid foundation for the selection of reasonable corrosion test methods and techniques in the future research for Mg-alloys, which will avoid erroneous conclusions resulting from improper testing and analysis.

Hot functional test (HFT) involves a number of pre-operational exercises without fuel performed to confirm the operability of newly constructed nuclear power plants in the conditions expected during both normal and off-normal operations of a pressurized water reactor (PWR). HFT water chemistry provides an opportunity to produce a stable and protective oxide scale on the key equipment in the primary coolant of PWR which can greatly reduce the corrosion rate of the substrate, the release of the metal ions and the incorporation of activated corrosion products during the subsequently long-term normal operations, and furthermore, relief the dose rate and decrease the corrosion rates of the related component materials for the nuclear power plants. HFT water chemistry adopted in PWR nuclear power plants and the evaluation methods for the HFT water chemistry optimization are reviewed in the present work. The effect of boric acid, lithium hydroxide, pH_T, dissolved hydrogen and Zn injection on the corrosion behavior of key components materials are analyzed. Challenges and trends for HFT water chemistry optimization in the future are also addressed.

Organic coating is widely applied to hinder the corrosion of large-scale engineering facilities, such as offshore platforms, oceangoing freighters, oil and gas pipelines and rail equipment etc. However, coatings are often severely deteriorated in harsh service environments, thus leading to corrosion of metallic substrates, which may not only threaten the service safety of the engineering facilities but also cause significant economic losses. Moreover, the coating degradation is an unavoidable and spontaneous process, and it should be mentioned especially that some hidden coating defects are hard to be detected. Therefore, it has become a research hotspot to develop coatings with function of defect self-disclosure for early detection and maintenance of defects by applying color reaction or fluorescence probe technology. In this review, we summarize the latest advances in coatings of defect self-disclosure, as well as the relevant trigger mechanisms and preparation strategies. First, the coatings of defect self-disclosure can be classified as corrosion-triggered type and mechanical-triggered type based on their mechanisms. Then the corrosion-triggered coatings may be subdivided into pH response and metal ion response according to the fluorescence change or color reaction. Moreover, it sorts out the diverse characteristics of those coatings such as their sensing principles, influencing factors, advantages and drawbacks, and fluorescence/coloration performances. Second, two kinds of preparation strategies for coatings of defect self-disclosure are introduced, one is grafting indicator groups onto polymer chain segments to prepare coatings of intrinsic defect self-disclosure, and the other is to incorporate nano-containers loaded with indicator as the functional filler. The differences and limitations of these strategies are compared and analyzed, further focusing on the key role of nanocontainers and their compatibility with different types of coatings of defect self-disclosure. In addition, the corrosion inhibitors, healing agents, and polymer microcapsules in the coatings of defect self-disclosure can not only realize defect indication but also endow their corrosion self-healing performance for boosting their application in the industrial field. Finally, it is envisioned the development prospect of coatings of defect self-disclosure to provide theoretical guidance for the design and application of the coatings of defect self-disclosure.

Risk-based inspection (RBI) is a kind of equipment risk management technology adopted in Western developed countries in the past 30 years, which is widely used in the field of petrochemical industry. Based on so-called fast process condition, RBI recommends inspection strategies, that predict the remaining life of the equipment, thereby providing inspection solutions with higher efficiency and lower costs. RBI is a risk assessment and management process that provides a way to determine the best checks. RBI can identify high-risk and low-risk devices and focus inspection resources on high-risk devices at the same time. This paper introduces the types and implementation process of RBI technology and methods, as well as the research progress and status quo of RBI at home and abroad, reviews the research status and corrosion problems of RBI technology in typical petroleum refining and chemical fields, analyzes the application of risk priority number (RPN) in risk testing and the dynamic testing method based on risk testing. The advantages and existing problems of RBI technology are expounded, and the development direction of RBI risk assessment is forecasted on this basis.

Lead-cooled fast reactor is a promising reactor type of the fourth-generation reactors. In the design of the cladding material, it is necessary to pay attention to the compatibility of the cladding material with the molten Pb-Bi alloy, and its resistance to liquid metal corrosion, especially, the properties of structural materials will be significantly degraded by the synergistic action of corrosive molten Pb-Bi alloy and external stress. The Small Punch Test (SPT) is a testing method, that uses a small size sample to assess the changes in the mechanical properties of a structural material in service conditions. This method can extract samples directly from the structural material in use without compromising its integrity. Therefore, the SPT is very suitable for situations where the number of materials under study is limited or where materials in service are studied. This paper briefly introduces the SPT technique, summarizes the research on the correlation between the SPT and the standard size test at home and abroad, expounds the research on mechanical properties of key materials by using small punch technique, especially expounds the application of SPT in the study of liquid metal embrittlement effect (LME) of structural materials. The results can provide technical methods and theoretical support for the application of small punch technique in the study of liquid Pb-Bi alloy induced embrittlement of engineering materials.

CO₂ induced pipeline corrosion is one of main concerns for the safe implementation and large-scale application of Carbon Capture, Utilization and Storage (CCUS) technology. Reasonably limiting the water content in supercritical CO₂ transport environments containing multiple impurities is crucial for the corrosion control of the pipeline. Herein, the effect of water content on the corrosion behavior of X65 pipeline steel in supercritical CO₂ transport environments with/without impurities of O₂, H₂S, SO₂ and NO₂ was investigated by means of simulated corrosion test with high-temperature and high-pressured autoclave, and surface analysis technology. Concurrently, the influence mechanism of impurities on the corrosion of the steel in supercritical CO₂ transport environments with different water contents was discussed. The results show that X65 steel only undergoes slight corrosion in supercritical CO₂-H₂O environment even if the water content reaches a saturated solubility of 0.4114%, and the corrosion rate is 0.0013 mm/a. However, when O₂, H₂S, SO₂ and NO₂ coexist in supercritical CO₂-H₂O environment, the corrosion rate of X65 steel increases from 0.0181 mm/a to 0.2901 mm/a as the water content varies from 0.002% to 0.4114%. The impurities and their interactions significantly promote the formation of corrosive aqueous phase, therefore exacerbating the corrosion of X65 steel. The corrosion process of X65 steel in the environment with low water content is controlled by the products of impurity reactions, whereas the impurities and the products of impurity reactions jointly dominate the corrosion process of the steel in the environment with high water content.

Erosion corrosion behavior of a newly developed high strength low alloy (HSLA) steel in flowing 3.5%NaCl solution was systematically investigated via a home-made rotating erosion device, mass loss measurement, electrochemical impedance spectroscopy and potentiodynamic polarization curve measurement, as well as macroscopic/microscopic characterization of corrosion morphology and Raman spectroscopy. The results revealed that the mass loss of the HSLA steel in flowing 3.5%NaCl solution exceeded that in static immersion test by over 10 times. Failure of the HSLA steel in both static immersion and dynamic erosion conditions exhibited three distinct stages. Degradation of the HSLA steel in static immersion conditions primarily manifested in the second and third stages. In contrast, the corrosion resistance of the HSLA steel in dynamic erosion conditions rapidly declined in the first stage. Flow erosion may hinder the formation of a stable corrosion product scale of α-FeOOH. The relevant accelerating corrosion mechanism may primarily be ascribed to the following two aspects: accelerating the mass transfer of O₂, Cl^- and other species, and compromising the passivation film as well as the integrity of the corrosion product film.

The inhibition action of Machilus yunnanensis leaves extract (MYLE) on Al-plate in 1.0 mol·L^-1 HCl solution were studied by means of mass loss method, electrochemical tests, inductively coupled plasma optical emission spectrometer (ICP-OES), metallographic microscope, scanning electron microscope (SEM) and contact angle measurements. The results show that the maximum inhibition efficiency of 1000 mg·L^-1 MYLE at 20^oC can reach as high as 93.5%. The inhibition efficiency increases with the increase of MYLE concentration, while the higher the temperature, the weaker the inhibition performance. The adsorption of MYLE on Al surface is mainly based on chemisorption, which conforms to Langmuir isotherm at lower temperatures and Freundlich isotherm at higher temperatures. The corrosion kinetic reaction of Al in HCl solutions without or with MYLE is in accordance with Arrhenius formula and transition state theory equation. In the presence of MYLE, the relevant apparent activation energy (E_a), pre-exponential factor (A), apparent activation enthalpy (ΔH_a) and apparent activation entropy (ΔS_a) are all increased. MYLE is a mixed inhibitor through “geometric blocking effect”. Nyquist diagram is mainly composed of a capacitive reactance arc in high frequency region and an inductive reactance arc in low frequency region. With the increase of MYLE concentration, both the charge transfer resistance and inductance resistance increase. After the addition of MYLE, the concentration of Al³⁺ in HCl solutions is significantly dropped, and SEM morphology further confirms that MYLE can efficiently slow down the corrosion degree of Al-plate.

Aluminized coatings were deposited on K452 superalloy by chemical vapor deposition (CVD) technique at the temperatures 850, 950 and 1050^oC, respectively. The effect of deposition temperature on the corrosion behavior of K452 alloys without and with CVD aluminized coatings was comparatively investigated beneath deposits of Na₂SO₄ and Na₂SO₄ + NaCl (3 ± 0.2 mg/cm²), respectively in air at 750^oC. Then their cross-sectional morphologies and phase structures were characterized by SEM/EDS and XRD. The results showed that all the aluminized coatings exhibited better corrosion resistance to the deposits of Na₂SO₄ and Na₂SO₄ + NaCl as compared to the bare K452 alloy after 50 h of corrosion. Notably, the corrosion resistance of the coatings was increased with the increase in deposition temperatures.

Aluminide coating was prepared on Inconel 718 superalloy by chemical vapor deposition (CVD). The hot corrosion behavior of Inconel 718 without and with aluminide coating beneath a thin film of salt mixture of Na₂SO₄ (95%) + NaCl (5%) in air at 750, 850 and 950^oC was studied respectively. The results indicate that Inconel 718 alloy shows poor corrosion resistance, and the higher the temperature, the more serious the corrosion. In the early stage of hot corrosion, the surface corrosion products are mainly composed of Cr₂O₃ and Fe₂O₃. As the corrosion time increases, spinel oxide becomes the main corrosion products. In addition, the scale on Inconel 718 alloy formed at 850 and 950^oC is loose and porous, while cracking and peeling were observed. For the aluminide coated alloy, it performs well with enhanced corrosion resistance, while an Al₂O₃ scale is formed on the coating surface during corrosion. Although the coating underwent significant degradation with the increasing corrosion temperature and/or corrosion time. Besides, the formed corrosion scale is not tightly boned to the coating, while the defects such as cracks or voids are observed. Even so, the coating can still protect the substrate effectively to a great extent.

The effect of diverse marine zones on the corrosion behavior of low alloy steels exhibits unique environmental characteristics, leading to significant differences in the corrosion rate of steels, as well as the composition and structure of rust scales. In this paper, the corrosion behavior of S420 steel, exposed in four different marine zones, i.e. atmospheric, splash, tidal, and immersion zones in the sea area of Qingdao by 36° 06' N and 120° 25' E for one year, was assessed by means of mass loss measurement, macroscopic and microscopic morphology observation, three-dimensional morphology detection, and corrosion product analysis. The results show that S420 steel exhibits the highest corrosion rate in the tidal zone and the lowest corrosion rate in marine atmosphere. Which may be attributed to the water-holding ability of the rust scale, thus providing sufficient electrolyte for the cathodic reaction. On the other hand, in the tidal zone, the wet-dry cycle results in the increase of the Cl^- concentration, accelerating the anodic reaction. The formed corrosion products are mainly composed of γ-Fe₂O₃, Fe₃O₄ and α/γ-FeOOH. The persistent presence of the electrolyte film may facilitate the formation of γ-FeOOH, making it dominant in the rust scales formed in tidal zone and full immersion zone. In the splash zone, the production of Fe₃O₄ may be promoted due to the synergist of adequate oxygen supply and wet-dry cycle, thus Fe₃O₄ is dominant in the formed rust scale. In the marine atmosphere, the thickness of the formed rust scale is the smallest, and the value of α/γ^* is the largest, which has protective effect against further corrosion of the steel substrate to certain extent. In the tidal zone, the thickness of the formed rust scale is the highest and the value of α/γ^* is the lowest, which is loose and porous, and the number and width of cracks within the rust scale are larger and wider, resulting in worst protective effect for the substrate. In other words, the S420 steel exhibits obvious localized corrosion characteristics with the maximum depth and high volume of pits in the tidal zone.

IN625 coating was laser clad on the surface of QT600 nodular cast iron, and the microstructure and composition of the clad coating were characterized by means of optical microscope and scanning electron microscope with energy dispersive spectroscope. The electrochemical corrosion behavior of the IN625 clad QT600 nodular cast iron was examined in 3.5%NaCl solution. Meanwhile, a numerical model of the transient evolution of micro-crack growth induced by corrosion of IN625 laser cladding layer was established, considering the corrosion process induced by the existence of micro-cracks in the cladding layer working in a harsh environment. The transient evolution of ion concentration, ion migration, pH value, electrode potential and corrosion rate during corrosion were analyzed. The results show that the corrosion resistance of IN625 clad QT600 nodular cast iron is significantly superior to that of the bare QT600 nodular cast iron.

2205 stainless steel is commonly used in pipeline systems. In the presence of flowing seawater the failure of passivation film on tubing can easily lead to accidents such as pipeline leakage. Therefore, it is of great significance to acquire the impact of flowing seawater on the pitting corrosion behavior of 2205 stainless steel with different surface treatments. Hence, 2205 stainless steel was firstly subjected to polish-treatment and passivation-treatment respectively, and then the pitting behavior of which in flowing seawater was assessed by means of electrochemical testing methods such as potentiodynamic polarization curve, electrochemical impedance spectroscopy, and Mott-Schottky curve as well as characterization of their morphology variation with corrosion process. It was found that there were obvious pits formed on the surface of either the polished or passivated steel, with pitting potentials ranging from 0.9 V to 1.2 V. The pitting resistance of the steel is higher in static seawater rather than in flowing seawater, but as the flow rate increases, the pitting resistance of the steel does not change significantly, however, the surface passivation film loses its re-passivation ability in flowing seawater. The passivation film on the surface of 2205 stainless steel exhibits two semiconductor characteristics: n-type and p-type, indicating that the passivation film presents a double-layer structure, mainly composed of oxides of Fe (outer portion) and Cr (inner portion). After passivation treatment, the pitting corrosion resistance of the steel increased, but the semiconductor properties of the passivation film did not show significant changes. The flowing seawater could reduce the pitting corrosion resistance of the steel, but the difference in the surface passivation film characteristics of the steel pre-treated by two methods could result in different sensitivity to pitting corrosion of the 2205 stainless steel in flowing seawaters.

The study on the preparation and properties of new anti-rust pigments is of significance for the development of anticorrosion coatings. In this paper, phytates were prepared by reaction of sulfates with sodium phytate. The phytates were characterized using SEM, EDS, FT-IR, and XRD analysis. The results showed that the prepared phytates were amorphous containing obvious phosphate groups, and presented as spherical particles with a diameter of 300-400 nm. The solubilities of phytates in aqueous solution were analyzed through titration test. The corrosion behavior of Q235 steel in phytate-extracting solutions, which were acquired by soaking aluminum-, magnesium-, calcium-, manganese- and zinc-phytates, respectively, in 3.5%NaCl solution and then leaching, were studied via immersion test, Tafel polarization, and electrochemical impedance spectroscopy. The findings revealed that the corrosion rate of carbon steel increased in aluminum phytate-extracting solution due to the production of aluminum-acid (Al(OH)₃). However, the corrosion rates decreased in the other four extracting solutions. Notably, the inhibition rate of zinc phytate was approximately 92.46%.

As one of the most common methods for galvanic corrosion control, organic coating has wildly used in an aerospace field. However, the failure of organic coatings often leads to the deterioration of mechanical properties of the dissimilar metal assemblies. In this work, selected organic coatings were applied on plates of 300M steel, 2024, and 5A06 Al-alloy respectively, then which were coupled with Ti-alloy plate by different modes. Afterwards, the dissimilar metal assemblies were subjected to lab accelerated tests in conditions of hot-humid, with mucedine, and of salt-spray in succession. Then, the acquired test results were analyzed and a comprehensive evaluation model for organic coating failures was established according to the so-called “Analytic Hierarchy Process (AHP)”, and which was verified by the measured results of electrochemical impedance spectroscopy (EIS) of the above assmeblies after lab accelerated tests. Furthermore, the mechanical properties of the dissimilar metal assemblies were examined by using a universal tensile testing machine after accelerated tests, and so that the relationship between the failure degree of organic coatings and damage degree of mechanical property of the dissimilar metal assemblies was established. The results indicate that the tensile strength and fracture elongation of the assemblies decrease to a certain degree after accelerated tests, which depend on the coupling modes. Meanwhile, there is a significant negative correlation between the mechanical properties and the comprehensive evaluation values for the dissimilar metal assemblies.

The effect of surface treatments of Eco Pickled Surface (EPS), picking and blasting on the hydrogen embrittlement (HE) susceptibility and hydrogen permeation kinetic of QStE700TM high-strength structural steel was comparatively assessed via slow strain rate tension (SSRT) and double electrolytic cell electrochemical hydrogen permeation device. The influence of surface treatment processes on the HE susceptibility of QStE700TM steel was discussed in terms of the variations of residual oxide scale, hardness and residual stress on the surface of steel plates subjected to different surface treatments. The results showed that the HE susceptibility of QStE700TM steel treated by EPS technique was only 8.1%, which is 12.7% and 20.5% lower than that by pickling and blasting, respectively. It would be related to the less residual oxide scale and the existed residual compressive stress on the surface of the steel plate treated by EPS. In addition, smaller hydrogen diffusion flux (J_∞L) and effective hydrogen diffusion coefficient (D_app) and larger lag time (t_L) and cathode side subsurface hydrogen concentration (c₀), should be responsible for the lower HE susceptibility of the steel samples treated by EPS. Take all factors into account, the EPS is a new, reliable, low-carbon and environmentally friendly surface descaling technology for high-strength steel.

In practical application, the selective oxidation of Ag₃Sn in Sn-Ag-Cu (SAC) solder will take place to form pure Ag, resulting in the formation of Ag/Sn galvanic couple. As development of electronic devices tends to miniature while high performance, the solder joints decrease in size, the in-between gaps become narrower, these factors lead to the increase in the intensity of the local electric field around solder joints. As a consequence, the corrosion behavior of SAC solder may change. In this paper, the corrosion of Ag/Sn galvanic couple under different applied potentials was studied by open-circuit potential and potentiodynamic polarization test and bipolar electrochemistry test. The results show that the OCP of Sn was lower than that of Ag. At high applied potential, Sn suffered severe corrosion while the formation of AgCl inhibited the dissolution of Ag; at low applied potential, Sn suffered cathodic corrosion.

Corrosion inhibitor is the most commonly used for corrosion control in oil production, but the relevant inhibition mechanism in complex CO₂ containing multiphase flow environment is still unclear. The effect of two typical oil-soluble and water-soluble imidazoline inhibitors on CO₂ induced corrosion of carbon steel in oil and water alternatively wetting conditions was investigated. It was found that the corrosion inhibition effect of the water-soluble imidazoline was better than that of the oil-soluble imidazoline, and the difference was mainly attributed to the performance of interface oil/water. The oil-soluble imidazoline molecules can improve the inhibition effect by enhancing the self-repair on the oil phase side, while the water-soluble imidazoline molecules can effectively inhibit the generation and growth of water droplets at the interface oil/water, weaken the rupture of CO₂ to the oil layer, and enhance the corrosion inhibition in dynamic wetting conditions.

In this work, the electrochemical properties and stress corrosion cracking (SCC) behavior of 904L super-austenitic stainless steel with various kinds of microstructure in simulated primary water were studied through potentiodynamic polarization curve measurement, electrochemical impedance spectroscopy (EIS) and U-bend immersion tests. The results show that the corrosion process of 904L stainless steel in simulated primary water is completely controlled by electrochemical reaction. Temperature has a strong influence on the corrosion resistance of 904L stainless steel. With the increase of temperature, the polarization resistance decreases; the passive range narrows down; corrosion potential shifts negatively, and corrosion resistance declines sharply. U-bend immersion test results prove that 904L stainless steel with the three kinds of microstructure has certain SCC susceptibility in simulated primary water. The corrosion products exert a two-layered structure, where the inner layer is uniform and thin black corrosion product, and the outer layer is granular and coarse white corrosion products. Among the three kinds of microstructure, the sensitized 904L stainless steel presents the highest SCC susceptibility, while solid solution treatment can decrease SCC susceptibility.

The corrosion behavior and mechanism of medium entropy equiatomic CoCrNi alloy (MEA) in various NH₄Cl solutions (i.e., with 1%, 3% and 8% NH₄Cl) were systematically studied by electrochemical test, statistical analysis, and immersion corrosion test. The results show that with the increase of NH₄Cl concentration, the corrosion potential (E_corr) of the MEA shifts negatively, the passive current density (I_p) increases, and the corrosion rate rises, indicating that the corrosion resistance of the alloy decreases. When the concentrations of NH₄Cl solution are 3% and 8%, the anodic polarization curve displays a clear active-passive transition zone, which means that the passivity of the MEA is reduced. In addition, as NH₄Cl concentration increases, the defect density within the passivation film on the MEA increases significantly, the thickness of the film decreases, and its stability declines, which weakens the protection ability of the film. The combined effect between NH₄⁺ and Cl^- promotes the nucleation and development of metastable pitting corrosion, while in the high concentration of NH₄Cl solution, the metastable pits are difficult to be re-passivated, and easy to develop into steady pits. In general, the main corrosion form of the MEA is pitting corrosion.

There is limited studies available on the corrosion of carbon steel in freshwater surroundings. Herewith, plates of two ship steels CCSA and Q235B steel were exposed to different sites such as the atmosphere, waterline, and underwater in freshwater surroundings of the Changjiang River (Yangtze River) for 0.5, 1, 2, 3, 4, and 7 a, then there corrosion behavior was assessed by means of morphology analysis, mass-loss measurement, XRD, and electrochemical techniques. Results show that the two carbon steels suffered from significant corrosion in the freshwater surroundings of the Changjiang River, exhibiting nearly the identical corrosion morphology. Their corrosion processes follow a power function law. After 7 years, the corrosion rates of CCSA were found to be 8, 77 and 40 μm·a^-1 in the atmosphere, waterline, and underwater, respectively, while the corrosion rates of Q235B were 9, 80, and 41 μm·a^-1 in the same conditions. Among others, the corrosion on the waterline was the highest. The composition of the corrosion product of the two carbon steels was similar, primarily including SiO₂, α-FeOOH, γ-FeOOH, Fe₂O₃ and Fe₃O₄/γ-Fe₂O₃. Based on the comprehensive electrochemical analysis results, CCSA demonstrated better corrosion resistance than Q235B. Regarding to the test results in various test sites of freshwater surroundings of the Changjiang River, the corrosion rate of the carbon steels may be ranked in descending order as follows: waterline> underwater > atmospheric.

NH₄Cl was one of the important factors causing corrosion of tubing steel in shale oil environment. Herewith, the effect of NH⁺₄ concentration on the corrosion behavior of N80 steel in 3%NaCl solution saturated with CO₂ was studied by means of mass loss method, electrochemical methods, scanning electron microscope (SEM), 3D profilometer, X-ray diffraction(XRD), and X-ray photoelectron spectroscopy (XPS). The results showed that NH⁺₄ concentration had a dual effect on the corrosion rate of N80 steel, i.e. promoting and inhibiting the corrosion rate. When the NH⁺₄ concentration was 0~500 mg/L, the uniform corrosion rate of N80 steel increased with the increasing NH⁺₄ concentration, while in the NH⁺₄ concentration range of 1000~2000 mg/L, the uniform corrosion rate of N80 steel decreased with the increasing NH⁺₄ concentration, however, the pitting corrosion rate showed a similar trend as the uniform corrosion. When the NH⁺₄ concentration was 500 mg/L, the uniform corrosion rate and pitting corrosion rate of N80 steel were the highest. Competition adsorption occurred between NH⁺₄ and Cl^- on the metal surface at NH⁺₄ concentrations ≤ 500 mg/L, while NH⁺₄ adsorption inhibited corrosion when NH⁺₄ concentration exceeded 500 mg/L.

In fact, Ni-Cr-Mo-V high strength steel is widely used as engineering structure material of ships- and equipment-building for the exploration of polar resources. However, high strength steel will suffer from corrosion in low temperature seawater environment. In case when the structure component of Ni-Cr-Mo-V high strength steel is subjected simultaneously to stress and corrosive seawater in this polar low temperature environment, its corrosion failure probability will be greatly aggravated. Therefore, it is of significance to clarify the service performance of Ni-Cr-Mo-V high strength steel in this environment. As thus, the corrosion behavior evolution of the steel in simulated low temperature seawaters with variation of dissolved oxygen contents was assessed in lab, while a four-point bending device was adopted as a means of applying stress on the testing steel. Results show that while a stress was applied on the test steel through banding in low temperature seawater, the increase of dissolved oxygen content will accelerate the formation of corrosion products on Ni-Cr-Mo-V high strength steel; correspondingly, Cr and Ni in the corrosion product layer decrease, which reduces the protective effect of the corrosion products layer on the substrate; when the dissolved oxygen content and the applied stress increase simultaneously, the Ni-Cr-Mo-V high strength steel will be further pseudo-passivated, resulting in an increase in its free-corrosion current density. It follows that in low temperature seawater environment, the applied stress and dissolved oxygen have a synergistic effect on the corrosion of Ni-Cr-Mo-V high strength steel, which promotes the corrosion reaction of Ni-Cr-Mo-V high strength steel, resulting in the aggravation of surface corrosion and the decrease of the protective effect of corrosion products on the steel substrate.

Pipeline integrity is maintained mainly by coating and cathodic protection (CP). The interaction between hydroxyl ions produced by CP-driven cathode reactions, such as water reduction, and carbon dioxide in soil generated by the decay of organic matter may develop high-pH of concentrated carbonate-bicarbonate electrolyte. The dominant anodic dissolution process of the corrosion of pipeline steel in the exposed environment could cause the degradation of the pipeline. In addition, aggressive ions, such as chloride ions, existed in soils would have an accelerating effect on the anodic process. The effect of 0.4 T magnetic field on the anodic process of X70 pipeline steel in sodium carbonate solution with and without chloride ions was studied using anodic polarization curve measurement, potentiodynamic scanning and potentiostatic polarization measurement. The anodic polarization curves of X70 pipeline steel in sodium carbonate solution show that the applied magnetic field increases the current density of oxygen evolution reaction at a high potential range, while has no significant effect on the anodic reaction at the passive range. In the sodium carbonate solution containing chloride ions, when the potentials for potentiostatic polarization are located in the passive range near the transition range of the potentiodynamic polarization curve; the potentiostatic polarization curves exhibit the characteristic of rapid active dissolution, and the applied magnetic field inhibits the anodic dissolution. When rapid anodic dissolution reaction and oxygen evolution reaction occur simultaneously at a high potential range, the effect of the magnetic field is not significant. The difference in anodic polarization current density obtained by potentiodynamic scanning polarization and potentiostatic polarization is due to the differences in electrode surface state and electrode reaction type caused by different polarization methods, leading to the alteration of the magnetic field effect.

The effect of a corrosion inhibitor 1.2.4-Triazole (TAZ) on the water quality of a simulated solution of the rotor cooling water and the corrosion inhibition performance for pure Cu-plate were assessed by means of pH meter, conductivity meter and dissolved oxygen analyzer, as well as measurements such as mass loss, dynamic potentiodynamic polarization curve, and electrochemical impedance spectroscopy. The results show that the addition of TAZ can reduce the pH value to a certain extent, but have little effect on the conductivity and dissolved oxygen content of the solution; With the increase of TAZ concentration, the corrosion rate and the corrosion current density for Cu decrease, i.e., its corrosion inhibition efficiency rises. The highest corrosion inhibition efficiency was 99.9% (loss-in-mass method) and 92.0% (EIS method) when the dose of TAZ was 10 mmol/L. The adsorption process on the metal surface was fitted using Langmuir isotherm, which confirmed that the adsorption of TAZ on the copper surface is a mixed adsorption. The theoretical calculations further proved that TAZ has a better adsorption effect on the surface of Cu, which can effectively inhibit the Cu corrosion in the simulated solution. It is expected that TAZ may have better corrosion inhibition performance for Cu in the rotor cooling waters, which is a kind of green corrosion inhibitor in spontaneous adsorption. Thus, the present results may be a meaningful reference for the application of corrosion inhibitor to protect the hollow-core copper conductors in the rotor cooling water for synchronous condenser.

In high-temperature and high-pressured environments containing CO₂ and H₂S, the failure risk of downhole string is extremely high, which seriously threatens the safety of production. Therefore, it is of great significance to evaluate the service life of tubular column. In this paper, taking offshore gas wells as an example, the Mises stress distribution and temperature distribution were obtained through the shaft-formation finite element model. Then, an appropriate CO₂/H₂S corrosion prediction model was used to calculate the corrosion rate of tubing. Finally, taking the safety factor of tubing as the evaluation criteria of safety performance, the evaluation of tubing service life is completed. The results showed that the Mises stress and temperature at all levels of wellbore increased with the increase of the running depth of tubular column. At the end of tubing, the maximum temperature and Mises stress are 207^oC and 447 MPa, respectively. In addition, the corrosion rate of the wellhead tubing is the highest, reaching 0.21 mm/a, according to the operation results of the corrosion model. Based on the above results, the safe service life of the tubing without any anti-corrosion measures is only 24 a. However, when corrosion inhibitors are injected, tubing can be used safely for more than 50 a when the corrosion inhibition efficiency is up to 90%.

The effect of different modification schemes for strengthening the coral coarse aggregate, namely direct incorporation of fly ash, cement slurry or cement-metakaolin composite slurry, on the corrosion rate of 2205 stainless steel bars in the coral concretes was comparatively assessed so that to search insight the way to improve the durability of stainless steel reinforced coral concrete structure. The results show that the 2205 stainless steel bar always maintained a passivation state in the coral concrete. The incorporation of fly ash can reduce the corrosion rate of 2205 stainless steel bar, but the direct addition of fly ash may significantly decrease the strength of coral concrete. With P.O 52.5 cement slurry or P.O 52.5 cement-metakaolin composite slurry as modifier can strengthen coral coarse aggregate, but the strength of coral concrete prepared with the modified crude aggregate has little difference with that of the control group, while the corrosion rate of 2205 stainless steel bar in the coral concrete strengthened with the coarse aggregate is significantly reduced. Among others, the corrosion rate of 2205 stainless steel bar is the lowest in the concrete of coarse aggregate reinforced with P.O 52.5 cement-metakaolin composite slurry In conclusion, using P.O 52.5 cement-metakaolin composite slurry to enhance coral coarse aggregate can effectively improve the durability of stainless steel reinforced coral concrete structures by providing high strength and greatly reducing the corrosion rate of 2205 stainless steel bar.

The synergistic effect of S^2- and Cl^- on corrosion resistance of 316L austenitic stainless steel in artificial seawater with different S^2- concentrations were studied by using electrochemical testing techniques, SEM, CLSM, EDS, and XPS. The results showed that S^2- and Cl^- have synergistic damaging effects on the corrosion resistance of 316L austenitic stainless steel. S^2- inhibited passivation film generation by competitive adsorption with OH^-, and the participation of S^2- in the passivation process is conductive to the formation of FeS and MoS₂, increasing the doping density but reducing the shielding performance of the passivation film, thus accelerating pitting induced by Cl^-. As the S^2- concentration increased from 0 to 100 mmol/L, the solution pH was increased from 8.2 to 12.8, resulting in a negative shift of the free-corrosion potential E_corr by 0.328 V and an increase in the corrosion current density I_corr approximately one-fold. When the S^2- concentration was greater than 0.1 mmol/L, 316L austenitic stainless steel lost its repassivation performance. When the S^2- concentration was greater than 100 mmol/L, 316L austenitic stainless steel lost its passivation performance.

The corrosion of metallic materials poses a threat to the safety and reliability of metallic facility and equipment, as well as exacerbating environmental pollution and economic losses. However, the use of sustainable, renewable and economical raw materials to prepare green corrosion inhibitors is still a challenging issue at this stage. Herein, biomass-based carbon dots (CDs) were prepared with lychee leaves as raw material, and their corrosion inhibition performance on Q235 steel in 1 mol/L HCl was assessed by means of mass loss measurement, electrochemical impedance spectroscope, and potentiodynamic polarization measurement. Results indicate that the obtained biomass-derived CDs contain numerous oxygen and nitrogen functional groups, which enable them to remain stable in 1 mol/L HCl solution and exhibit long-term stable corrosion inhibition performance.

In order to understand and monitor the process of stress corrosion crack propagation of engineering equipment in service, the study focuses on the propagation of stress corrosion cracks of a designed double cantilever specimen of high-strength Al-alloy with prefabricated crack. Firstly, the mechanism of stress corrosion crack propagation was described, and the linear relationship of the crack length with the variation of the strain in the x- and y-directions of the stress corrosion crack propagation tip was determined through Matlab simulation; The stress concentration area at the crack tip was further determined by Abaqus finite element simulation, afterwards, the distance between the position of optical fiber sensing probe and the crack tip was selected to be 10 and 15 mm respectively; The relevant sensing technology of stress corrosion crack propagation in fiber Bragg gratings was also studied, and then a grating temperature compensation model was proposed; Finally, the correlation between the crack length and the wavelength change of the fiber Bragg grating sensor during corrosion crack propagation was calibrated. The results showed that the correlation of the crack length and the wavelength change was R² =0.9893 and R² = 0.9870, respectively; Afterwards, an outdoor exposure test set was constructed in Wanning of Hainan Province, to achieve in-situ monitoring of stress corrosion crack propagation of Al-alloys through networking. The monitoring data showed that after adopting the suitable temperature compensation, the measurement error is only 2.61% for sensor positioned 10 mm near the crack tip, and the monitoring results can provide data support for the real operation of engineering equipment.