Aluminum is one of the most widely used non-ferrous metallic materials, while it is an active amphoteric metal and can be easily corroded. Adding corrosion inhibitors in corrosive media is an important strategy to prevent or slow down the corrosion of aluminum, which has been widely used in the chemical industry. With the improvement of environmental awareness and the implementation of sustainable development strategy, it is urgent to develop cheap, efficient and environmentally friendly corrosion inhibitors. Plant corrosion inhibitors are one of the hotspots in the field of corrosion inhibitor research due to their outstanding advantages such as abundant resources, biodegradability and environmental friendliness. This article summarizes the research status about the research methods, corrosion inhibition mechanisms, and extraction methods of plant corrosion inhibitors on Al in acidic, alkaline, and other media since 2008, and moreover, the future research directions and key scientific issues of plant corrosion inhibitors are also prospected.

The oxide scale is an important matter affecting the surface quality of steel, which seriously restricts the application of hot rolled steel in high-end manufacturing. However, there is still a lack of comprehensive reports on the applied control technology for the formed oxide scale on the steel during rolling process. Herewith, the applied control technology for iron oxide scale and relevant mechanism are introduced in terms of mechanical descaling for rolled steel, red iron oxide scale (red rust) on steel surface, anti-corrosive iron oxide scale on hot rolled steel, galvanization of hot rolled steel without pre-pickling, and friction and wear resistance of iron oxide scale etc. By taking the current market demand and the existing control technology into consideration, the main development direction of future research on the applied control technology for the iron oxide scale on hot rolled steel is introduced.

Power plant boilers are the key equipment for thermal power generation. During the combustion process, under the impact of the gas-solid two-phase flow of flue gas and fly ash, the heat exchange tubes of the boiler are prone to erosion-wear damage. The deterioration or even explosion of tubes seriously threatens the safe and stable operation of the power plant. In this paper, the causes of erosion, failure mechanism of heat exchange surfaces and prediction models of erosion rate were reviewed, including the cutting wear/deformation wear caused by fly ash in the furnace and the calculation model of the corrosion rate by considering various erosion parameters. Based on this, according to the specific environment of heat exchange surfaces in boilers, the influence of fly ash characteristics (shape, particle size and hardness), tube materials (carbon steel/alloy steel), and the service environment of heat exchange surfaces (the flow rate of flue gas in furnace, erosion speed/angle of fly ash, tube surface temperature) on the erosion-wear damage was summarized in detail. It is believed that erosion speed and tube surface temperature are the most important factors affecting erosion damage. Furthermore, from the perspective of alleviating erosion-wear, the research status of adding anti-erosion components and erosion-resistant coating materials on heat exchange surfaces was also reviewed. It was proposed that the main development directions of anti-erosion measures were to optimize the structure of heat exchange surfaces through flow field simulation and to apply WC-Co/Cr₂C₃-NiCr cermet coatings. At the same time, it was also pointed out that to clearly understand the relationship between the cost and protection effect of coatings, and further to optimize the coating preparation process, so that to reduce costs could provide an important economic guidance for the utilization of coatings. This review can provide a reference for the research on erosion-wear of heat exchange surfaces in boilers, as well as the development and application of protective measures.

Metal oxide electrode is widely used for pH examination in food, biology and medical industries due to its characteristics of wide pH response range (pH measurement range can reach 2-12, even 0-14) and easy to be miniaturized. It can be used for in situ measurement of pH value at the vicinity of metal/electrolyte interface, thus providing important parameters for deducing the possible electrochemical reactions, explaining specific corrosion behavior and revealing the relevant corrosion mechanism. In this paper, the response performance, performance parameters and the research progress of metal oxide electrodes made of iridium, manganese, titanium, tungsten and the relevant oxides were summarized. Among which, the iridium oxide electrode was most widely used as a pH detector for its stability and high response slope (-59.5 - -74.91 mV/pH). The commonly used preparation methods for micro metal oxide pH electrodes such as electrochemical deposition method, thermal oxidation method, sol-gel method, screen printing method, etc. as well as the effect of different process parameters were also summarized. The electrochemical deposition method had a broad application prospect, and with which the prepared electrodes had the characteristics of low cost, high response slope and fast response rate, but their potential drift for the long-term service needed to be solved. Aiming at the matter of potential drift and long aging time of metal pH electrodes, the effect of post-treatment processes such as hydration, heat treatment and hydrothermal treatment on the electrode performance were introduced. The applications of metal oxide pH micro-electrodes for the examination of pitting corrosion, galvanic corrosion, stress corrosion and other local corrosion, as well as for the monitoring cathodic protection were reviewed, including the micro metal oxide pH electrode, composite double-tube pH electrode and the combination of pH electrode and scanning electrochemical microscopy technology (SECM), etc. The metal oxide electrode was easy to be miniaturized and had a stable response, which made it show good response performance in the process of monitoring the change of pH value nearby the metal/electrolyte interface formed during local anodic corrosion or cathodic reduction reaction. Lastly, the preparation technology and application trend of the micro metal oxide electrode were also prospected.

Metallic materials for electrical equipment are affected by many factors related with environment during service, and their corrosion behavior is very complex, therefore, which is difficult to be accurately predicted. The development of computer technology and data analysis technology enriches the prediction methods for corrosion behavior of metallic materials with better accuracy. This paper summarizes and analyzes the existing common corrosion prediction methods in the field of corrosion, including function model, grey theory model, neural network prediction model, dose response function model and random forest model etc., and which then are classified into two types, namely corrosion-time models and corrosion-environment prediction models. Furthermore, the characteristics and application scope of different corrosion prediction models are introduced. Finally, prospects for the corrosion prediction of metallic materials are put forward especially in terms of the demands of power industry.

Epoxy composite coatings with different contents of cerium salt treated multi-walled carbon nanotubes (CeO₂@MWCNTs) were prepared on X80 steel. The corrosion behavior and tribological property of the composite coatings were studied. Meanwhile, the morphology, chemical composition and structure, as well as wettability and hardness of CeO₂@MWCNTs/EP composite coating were characterized by means of SEM, TEM and white light interferometer, EDS, XPS and FT-IR, contact angle meter and microhardness tester etc. The results show that there exist physical adsorption for the interface between nano-CeO₂ and MWCNTs in the prepared powder of CeO₂@MWCNTs, while the structure of epoxy can be changed due to the introduction of nano-CeO₂ particulates. CeO₂@MWCNTs is beneficial to reduce the micropores in the CeO₂@MWCNTs/EP composite coating, but the powders may agglomerate when the dosage reaches to 1.0%. It should be noted that CeO₂@MWCNTs in dispersive state can improve the corrosion resistance of the composite coating, but in agglomerated state which presents negative effect. The corrosion resistance of CeO₂@MWCNTs/EP composite coating first increases and then decrease with the increase of CeO₂@MWCNTs content, and among others, the corrosion current density of the coating with 0.5% CeO₂@MWCNTs/EP is the smallest, which is an order of magnitude less than that of the simple EP coating. CeO₂@MWCNTs possesses lubricating function, therefore, the friction coefficient and wear rate of the composite coating show a decreasing trend with the increasing CeO₂@MWCNTs content. The wear rate of 1.0% CeO₂@MWCNTs/EP composite coating decreases by 64.7% in comparison with the simple EP coating.

The 5083 Al-alloy coating (5083 coating) and Zn15Al coating were prepared on the surface of EH36 steel by arc spraying technology, and the corrosion resistance of the two coatings in neutral salt spray environment was comparatively studied by means of mass loss method, electrochemical tests, SEM and XRD etc. The results show that, with the progress of corrosion, the corrosion rate of the two coatings gradually decreases, and the corrosion rate of 5083 Al-alloy coating is significantly lower than that of Zn15Al coating. The morphological observations show that the corrosion products of 5083 Al-alloy coatings are dense and blocky, and there is no obvious infiltration of Cl^-. However, the corrosion products of Zn15Al coatings are loose and fine needle-like, and Cl^- is deposited in the corrosion product layer after 10 d of salt spray corrosion and then gradually penetrates into the coating matrix. The corrosion products of 5083 Al-alloy coating are mainly Al(OH)₃, and those of Zn15Al coating composed mainly of Zn(OH)₂ and Zn₅(OH)₈Cl₂·H₂O. Taking the calculation results of the solubility product constant K_spand supersaturation into consideration, it follows that the deposition of Al(OH)₃ requires a lower Al³⁺ concentration and presents a faster deposition rate. Therefore, the 5083 coating is more inclined to form a dense layer of corrosion products. This result is verified by the EIS test results. As corrosion time prolongs, the polarization resistance of the two coatings gradually increases, and the polarization resistance of the 5083 Al-alloy coating is higher than that of the Zn15Al coating, indicating that the densification of corrosion products is the main reason affecting the corrosion resistance of the two coatings.

The occurrence of atmospheric corrosion is always companied initially with the formation of electrolyte film on the surface of metals, and then the corrosion process is affected by soluble substances such as oxygen from the surrounding environment and the nature of metals themselves. The process of atmospheric corrosion reaction relates to the phase transition of the gas, solid, and liquid substance, as well as the material transfer among different phases. This study simulated the atmospheric corrosion process of the pure copper plate in humid and hot environmental conditions as well as sea fog atmosphere by the multi-factor orthogonal corrosion test. The corrosion mechanism of copper plates beneath thin liquid films in steady state environment was also studied. By calculating the state changes of the thin liquid film with the variation of temperature, humidity and other environmental conditions, the migration process of dissolved oxygen within the thin liquid films of different thicknesses and Cl^- concentrations was analyzed. The influence of environmental factors on the thin liquid film, electrolyte concentration, and corrosion kinetics was revealed eventually by comparing the experimental data and theoretical calculation results.

The corrosion behavior of Cu-bearing aged weldable steels with varied Ni levels of 2.5Ni, 2.0Ni and 1.5Ni was assessed via an indoor dry-wet alternating accelerated test, aiming to simulate the tropical marine atmospheric environment, by means of mass loss method, scanning electron microscopy (SEM), X-ray diffraction (XRD), electron probe microanalysis (EPMA) and electrochemical test methods. The findings demonstrate that in the simulated tropical marine atmospheric environment, the corrosion rates of the three experimental steels increase initially, then decrease and finally remain steady. Their corrosion rate decreases with increasing Ni concentration. The steel with 2.5Ni corrodes at a rate that is 25% less than that of 1.5Ni. The rust layer is rich mostly in Ni and Cu. The addition of Ni to the steel will result in the formation of NiFe₂O₄ in the rust layer, which favors the conversion of γ-FeOOH phase to α-FeOOH phase, thus increases the compactness of the rust layer. The higher the Ni content, the more obvious the effect, thereby, the better the protectiveness of the rust layer. The propensity for the free-corrosion potential and the resistance of the rust layer increase with the increasing Ni concentration. Therewith the rust layer can effectively inhibit the anodic dissolution and the transfer of charged particles within the rust layer.

Developing high-efficiency and eco-friendly corrosion inhibitors to replace traditional toxic and harmful ones is necessary to protect the ecological environment. Based on these premises, we employed electrochemical impedance techniques, gravimetric methods, and others to investigate the corrosion inhibition and mechanism of a low-cost drug, liraglutide (LNLP), used for human diabetes treatment, on copper in 0.5 mol/L sulfuric acid solution. The findings demonstrate that LNLP is a green, eco-friendly type of corrosion inhibitor, and is effective in inhibiting the corrosion of copper in sulfuric acid. The electrochemical results show that LNLP could slow down the corrosion rate of copper in 0.5 mol/L H₂SO₄ solution by increasing the film and charge transfer resistance and reducing the film and double-layer capacitance. When the concentration of LNLP is only 1 mmol/L, the η is as high as 99.95%. Potentiodynamic polarization curves results indicate that LNLP is a modest mixed-type inhibitor that can inhibit the anodic and cathodic reactions of copper. Based on the adsorption curve and theoretical calculation, the interaction between LNLP and the copper surface and the structure-performance relationship of LNLP molecule are revealed. The relevant results show that the adsorption of LNLP on the copper surface is parallel, providing max protection for copper. The adsorption of LNLP molecules on the copper is mainly through the nitrogen, oxygen heteroatoms, and conjugated ringy functional groups within the molecules, forming a single-molecule film through the synergistic effect of physical and chemical adsorption, isolating corrosive media from the copper surface.

The effect of water-soluble corrosion inhibitor on the corrosion behavior of pipeline Q235 steel beneath artificial sediments in a liquid of simulated building pipeline sewage was assessed by means of mass-loss measurement, potentiodynamic polarization curve measurement, electrochemical impedance spectroscopy and wire beam electrode (WBE) technique. The results show that the water-soluble corrosion inhibitor IMC-80-N-4 can effectively alleviate the corrosion of Q235 steel in the test environment. With the increasing concentration of the corrosion inhibitor, the inhibitor film formed and became compact gradually on the steel surface. The corrosion inhibition effect of 25 mg/L water-soluble corrosion inhibitor is the best, which reduces the free-corrosion current density of the steel substrate by two orders of magnitude. Moreover, the galvanic current in the area covered with sediments was also reduced. Therefore, regular injection of 25 mg/L water-soluble corrosion inhibitor in the construction pipeline can effectively inhibit the corrosion of Q235 steel, besides, the inhibitor exhibits a good effect even under the condition of sediment coverage. That can significantly improve the safe operation of the construction pipeline, so that increase and extend the service life of the building.

Carbon dioxide (CO₂) is a gaseous pollutant found in museums that can seriously damage the original appearance of copper artifacts through local acidification and corrosion. Aiming to simulate the CO₂ induced corrosion of the real copper artifacts, a quartz-crystal microbalance (QCM) in conjunction with corrosion products analysis techniques is used to reveal the initial corrosion behavior and regularities of Cu in the CO₂ containing environment. Furthermore, vapor-phase corrosion inhibitors (VCI) compounded with benzotriazole (BTA) and L-cysteine (CYS) were specifically formulated to improve the anti-corrosion ability of Cu. In this work, we investigated the anticorrosive mechanism of VCI on Cu by means of electrochemical impedance spectroscopy (EIS) technology and density functional theory (DFT). The results demonstrated that with the increase of CO₂ concentration and relative humidity content of the environment, the Cu corrosion was accelerated, and the initial corrosion products consist mainly of Cu₂O, CuO and CuCO₃∙Cu(OH)₂ after exposure to CO₂ environment. BTA and CYS have significant synergistic anti-corrosion performance for Cu. When the compound radio of BTA to CYS is 4∶1, the highest corrosion inhibition efficiency is 86.2%. Which may be ascribed to that the CYS molecular with relatively smaller size can fully fill the defects of the BTA film, thus causing a greater densification of the anti-corrosion film.

The corrosion fatigue crack growth rate (CFCGR) of nickel base alloy 617, a candidate material for advanced ultra-supercritical unit, in 650 °C/25 MPa supercritical water was studied. The constant stress intensity factor (K) method is used for dynamic loading, and the DC potential drop (DCPD) method is used to measure the crack length in real time. The effect of maximum stress intensity factors (K_max=30, 32, 36, 40 MPa·m^1/2), stress ratios (R=0.3, 0.4, 0.5, 0.6), loading frequencies (f=0.01, 1 Hz) and waveforms (sine wave, triangular wave and trapezoidal wave) on CFCGR were investigated. The results show that the CFCGR increases monotonously with the increase of K_max, and the relationship between them is approximately linear. CFCGR increases with the decrease of R. With the increase of loading frequency, the CFCGR decreases. Under the two frequencies (f=0.01, 1 Hz), the sine wave and triangular wave loading have no obvious effect on the CFCGR. Trapezoidal waves result in larger CFCGR than continuous cycles without hold time.

Carbon steel is the main material for power plants, oil and gas pipelines. Flow accelerated corrosion is the main factor causing pipeline failure in power plants, especially the secondary circuit pipeline system of the pressurized water reactor (PWR) nuclear power plant. In this paper, a home-made flow accelerated corrosion test rig and array electrode technology was used to study the effect of different flow rates on the flow accelerated corrosion rate distribution of 20# carbon steel elbow at 120 °C. The correlation between hydrodynamic parameters and corrosion rate was analyzed based on hydrodynamic simulation. The results show that the maximum corrosion current density is located at the external bending side of the elbow at different flow rates. With the increase of flow velocity, the flow accelerated corrosion rate increased significantly. In addition, the comparison of experimental data and simulation results show that the radial local velocity component can be used as an important parameter to predict the flow accelerated corrosion rate of carbon steel elbow. The empirical formula between the radial local velocity component and the corrosion rate was obtained by fitting based on the least square method. This research can be applied to design optimization, operation monitoring and maintenance strategy formulation of carbon steel elbow transport lines in thermal power, nuclear power and chemical industries.

Al-Zn-0.03In-1.30Mg sacrificial anode alloys with various Zn contents were designed and prepared. The effect of Zn content on the electrochemical properties of the Al-Zn-0.03In-1.30Mg anode alloys were investigated by AC impedance spectroscopy, galvanostatic- and potentiodynamic-polarization measurements. While the effect of Zn content on the microstructure and corrosion morphology of the alloys were analyzed by metallographic microscope, scanning electron microscope (SEM) and energy dispersive analysis (EDS). The results showed that with the increasing Zn content the grain size of Al-Zn-0.03In-1.30Mg alloys became finer with more uniform microstructure, whilst the free-corrosion current density shifted significantly in the negative direction. The addition of 0.60%-10.00% (mass fraction) Zn could effectively destroy the passive film on the alloy surface and improve the dissolution morphology of the anode alloy. But when the content of Zn excesses 5.00%, dendrites were generated, which would increase local corrosion tendency to make the alloy dissolve ununiformly with decreasing electrochemical properties. The anode alloys with 0.60%~2.00%Zn all exhibited high electrochemical performance, of which the surface dissolved uniformly with a capacity over 2570 A·h·kg^-1, and the working potential lower than -1.05 V (vs SCE). The anode alloy with 0.60% Zn could significantly reduce the heavy metal Zn pollution to the marine environment. Therefore, it could be used as environment-friendly sacrificial anode material.

The cavitation resistance of a new eutectic high entropy alloy NiCoCrFeNb_0.45 was assessed via a home-made jet cavitation experimental device. While a new characterization method for cavitation damage, based on image intelligent recognition, was developed by using gray level co-occurrence matrix and binary image method. Therewith, the digital analysis of cavitation damage distribution and the microscopic assessment of local cavitation damage could be realized. The results show that the primary cavitation damage mechanism of NiCoCrFeNb_0.45 is the deformable pits caused by repeated cavitation collapse, as well as the fatigue cracks induced by the work hardening. The dual-phase eutectic structure of NiCoCrFeNb_0.45 is composed of Laves phase with high hardness and FCC phase with high toughness, which achieves the balance between high hardness and high toughness. As a result, NiCoCrFeNb_0.45 has a superior cavitation damage resistance, compared with 04Cr13Ni5Mo and 45 steel. The characteristic parameters, such as standard deviation, energy value and entropy value of cavitation image, are extracted by gray level co-occurrence matrix, and these parameters show that the distribution of cavitation damage for NiCoCrFeNb_0.45 is the simplest, and the degree of cavitation damage is the lowest. The image binarization method could help to obtain the regularity of distribution of large-scale pits on the material surface. The cavitation damage ratio of NiCoCrFeNb_0.45 is 8.1%, which is significantly lower than that of the other two materials. This study provides a new reference for cavitation damage assessment and material protection for hydraulic machinery.

Erosion corrosion and sulfate reducing bacteria (SRB) induced corrosion bring harm to the safe operation of pipeline. In this article, the SRB induced corrosion of pipeline steel L360 in fluid scouring environment was studied comparatively by means of numerical simulation and simulation experiments. The predicted cloud map and particle motion trajectory map of the distribution for corrosion areas of pipeline steel were obtained by using computational fluid dynamics (CFD) simulation. Results showed that the most serious corrosion located at the bottom of the pipeline, the corrosion degree at the outlet of the pipeline was higher than that at the entrance of the pipeline. Electrochemical methods and surface analysis methods were used to characterize the SRB induced corrosion in solid-liquid two-phase flowing environment. Results show that when the biofilm of SRB did not exist on the metal surface (i.e., no biofilm of SRB has been formed on the steel through a pre-treatment), the scouring corrosion is dominant, the metal surface shows obvious scouring corrosion characteristics, and the corrosion products are mainly iron oxides. When SRB has formed a dense biofilm on the metal surface (after a proper pre-treatment), SRB corrosion dominates, and the biofilm will inhibit the scouring corrosion, but the life activity of SRB under the film will induce the electron exchange with the metal matrix, so that SRB induced corrosion occurs, and the corrosion products consist mainly of sulfur and iron compounds.

The corrosion resistance of 4Cr16Mo martensite stainless steels without and with 1%Cu addition (i.e., 4Cr16MoCu) in 3.5%NaCl solution was comparatively studied by three-point flexural loading stress corrosion test method. The results show that there is no significant difference in corrosion resistance between the two steels after tempering at 250 ℃. However, after tempering at 600 ℃, the corrosion resistance of 4Cr16MoCu steel is significantly enhanced. Through microstructure analysis, it is speculated that this is related to the precipitation of the Cu-rich phase. A stress corrosion model for the 4Cr16MoCu steel is proposed based on the characteristics and evolution process of corrosion morphology of the steel, i.e., in the early stage of corrosion, breaks of the passivation film may induce the emerging discrete anode- and cathode-spots on the steel surface, further result in an electrolytic polishing-like effect to peel off the surface passivation film and finally the pitting corrosion.

Sulfate is one of the main components of sea water. Concrete structures serving in marine environment may come into contact with sea water, thereby, a series of sulfate induced chemical reactions occurred to cause the destruction of concrete. According to the characteristics of corrosion products, the sulfate induced corrosion attacks may be divided into the following three types, i.e., ettringite sulfate attack, gypsum sulfate attack and carbonite sulfate attack. In this paper, the corrosion behavior of the ultra-high-performance concretes prepared with sea water and sea sand (SSUHPC), as well as those with fresh water and river sand (FRUHPC) were comparatively studied in an artificial sea water containing sulfates. Based on the study of the evolution of sulfate induced corrosion degradation process, the corrosion damage mechanism related with SSUHPC and FRUHPC was revealed by using MIP, SEM-EDS and XRD techniques, and the damage mechanism was summarized. With the progress of sulfate corrosion process, the cementite on the surface of concrete reacts with Mg²⁺ and SO^2-₄ to produce corrosion products such as AFt and gypsum sulfate etc. On the one hand, the formation of a large number of corrosion products may consume hydration products such as Ca(OH)₂ and C-S-H gel; on the other hand, the cementite on the surface of concrete loses strength and cementation, and then falls off. Due to the corrosion damage of the concrete surface layer, the aggregates and steel reinforce bars within the concrete are exposed, therewith, the steel bars will rust once they come into contact with the corrosive fluids within the environment. With the progress of sulfate corrosion, the formation of corrosion products Aft, gypsum sulfate etc.is speeded, and which cumulated on the exposed concrete surface. Hence, the mortar that loses strength falls off together with the steel bars from the concrete surface, so that to further expose the interior of the concrete, which in turn, act as a “new outer surface” of the concrete faced to the corrosive environment. Different from the traditional three types of sulfate corrosion failure forms, the damage forms of ultra-high-performance concrete are more complex, but these damage characteristics only occur within the millimeter range of the concrete surface, and the concrete still maintains excellent mechanical and durability characteristics internally, with little overall impact on the concrete structure. In sum, the SSUHPC and FRUHPC show excellent sulfate resistance.

Corrosion of steel bar induced by chloride salt attack is one of the main factors leading to the failure of recycled concrete. Hence, it is of great significance to study the microscopic diffusion behavior of chloride ions in recycled concrete for evaluating the durability of recycled concrete in marine environment. A new mortar layer is applied on the old mortar layer whose thickness changes, and the thickness changes of the old mortar layer are assumed to conform to the normal distribution of random number, so as to construct transition zones of different states between the new and old mortar interfaces. On this basis, the meso-structure of five-phase regenerated aggregate, namely coarse aggregate, new-old mortars and the transition zones of new-old interface, was established. Based on the diffusion theory, the chloride diffusion coefficients of each component was obtained, and the mesoscopic numerical model of chloride ion diffusion in the recycled concrete was established. The reliability of the chloride ion diffusion model of recycled concrete is verified by comparing with the existing experimental data. The effect of recycled coarse aggregate, old and new interface transition zone thickness, relative diffusion coefficient of the old interface transition zone, relative diffusion coefficient of old mortar and the adhesion rate of the old mortar on the chloride ion diffusion behavior were further studied. The results show that: compared with the natural aggregate, the adhesion of old mortar weakens the blocking effect of the regenerated coarse aggregate on the chloride ion attack. Although the area proportion of the interfacial transition zone is very small, however, the resistance to chloride ion attack of the reclaimed concrete decreases with the increase of the interfacial transition zone thickness and the diffusion coefficient. In addition, the chloride ion diffusion performance of the recycled aggregate concrete is enhanced with the increase of the adhesion rate and diffusion coefficient of the old mortar, and the enhancing trend is more significant with the increasing volume fraction of the reclaimed aggregate. Therefore, in order to prolong the durability of recycled concrete, it is of great significance to improve the anti-chloride ion attack of the interfacial transition zone and the old mortar, as well as to reduce the adhesion rate of the old mortar.

In order to reveal the effect of different interface treatment processes on the bonding properties of low shrinkage and high viscosity multi-element composite repair mortar (LSHVRM) to the repaired concrete workpiece, 54 repair test-pieces were designed. The effect of treatment processes, such as brushing migration corrosion inhibitor, spraying DPS reinforcing agent, brushing migration corrosion inhibitor and chemical conversion of corrosion products on steel bar on the anti-stripping performance of the repaired workpieces were studied especially, focusing on the influence of carbonization degree of concrete interface at the site to be repaired and whether there are steel bars buried or not. The results show that the carbonization degree of the surface of the repairing concrete has only a little effect on the bonding performance, namely the surface brushing migration type rust inhibitor resulted in an effect range between -1.4% and 6.8%. The spraying DPS reinforcing agent resulted in an increase range of 2.7%-7.4%. In case, rust steel bars emerged at the interface, the effect of steel brush treatment brought an effect range of -2.7% to 5.4%. However, The combination of spraying DPS reinforcing agent and brushing migration corrosion inhibitor could increase the bonding performance within a range of 0.6% and 6.9%. The spraying DPS reinforcing agent after the treatment with chemical conversion agent for rust steel bars could provide an increasing effect within a range of 4.5% and 16.6%. In general, the interface treatment process, such as steel brush treatment of steel bar, brush migration corrosion inhibitor and chemical conversion treatment of the rust steel bar, will bring little adverse effect on the bonding performance of the repaired concrete, while bring improvement effect within a small range, although these treatment methods has induced different degrees of carburization for the surface of repairing concrete.

A surface-tolerant epoxy anticorrosive primer was prepared on the surface of Sa2 grade steel. Its solid content was up to 80%, the drying speed was only 4 h, and the average adhesion was up to 10 MPa. The coating keeps intact with no cracking and no spallation after outdoor exposure for 5 a, and has excellent corrosion resistance to acid, alkali and salt solution. The electrochemical performance and corrosion mechanism of the coating were studied by means of FTIR, EIS and three-dimensional video microscope. The results showed that the impedance of the coating reached 10¹⁰ Ω·cm² after 2400 h seawater immersion, which showed excellent corrosion resistance. The impedance of the coating decreased first and then increased with the extension of immersion time. The densification of the coating is due to the cross-linking of epoxy resin and polyamide curing, so that can act as a good barrier to the corrosive medium. During the middle and late stage of the corrosion process, the stable complex formed by the reaction of zinc phosphate pigment with the rust on steel surface, can prevent the infiltration of corrosive medium, which may be the reason why the coating has excellent corrosion resistance and high tolerance to the substrate surface.

Nuclear containment vessel is the third barrier to avoid the nuclear leakage. It is noted that severe outer corrosion of steel liners happened in several containment vessels around the world, which greatly threatened the integrity and tightness of liners of containment vessel. The outer corrosion is a great safety risk because it is perceptually invisible and hard to be maintenance. To the authors' knowledge, researches related to the ratter of outer corrosion are scare. No authoritative corrosion mechanism has been proposed. Based on the operating reports of several nuclear power plants and a mesoscopic corrosion models established by COMSOL, the corrosion mechanisms of the outer corrosion of steel liners were analyzed in the views of effects of corrosive ions and foreign materials. Results revealed that a long-time exposure of steel liners in the marine environment will generate the non-uniform accumulation of corrosive ions on the outer surface of liners, which is the reason for the microcell corrosion of outer corrosion of steel liners. Corrosion rate in this condition is decided by the maximum content of the non-uniformly distributed chloride. Besides, foreign materials (mainly wood blocks) unintended left behind during pouring concrete will also lead to electro-chemical corrosion, in which macrocell corrosion plays an important role. The corrosion rate was accelerated along with the decrease of the touching surface size between foreign materials and steel liners and with the increase of area ratio of cathode and anode. Meanwhile, the corrosion rate can be effectively mitigated by enhancing the concrete resistivity. The achievements in this paper can provide technical reference for the aging mechanisms and aging prevention measures of nuclear containment.

The exposure tests of E690 steel were carried out in tropical marine atmosphere of high temperature, high humidity and high salt at Zhanjiang atmospheric corrosion test station for 15, 30, 90, 180 and 360 d. Meanwhile, the initial corrosion behavior of E690 steel in tropical marine atmosphere was studied by mass loss method and electrochemical measurement, combined with macroscopic and microscopic corrosion morphology observation and corrosion product analysis. The results showed that the corrosion rate of E690 steel was higher at the beginning, and then decreased with the prolongation of exposure time. After 90 d of exposure, the corrosion rate changed little and the corrosion tended to be stable. After 90 d of exposure, Cr has diffused into the rust scale, thus improving the compactness of the rust scale. The participation of Ni promotes the transformation of γ-FeOOH to α-FeOOH, which then improved the corrosion resistance of E690 steel and reduced its corrosion rate.

The effect of the adhesive barnacles, as a common fouling organism, on the corrosion behavior of Q235 steel was examined via immersion testing in natural seawater of depth 15 m at Zhanjiang Bay. After immersion in seawater for 15 and 30 d respectively, the tested steels were characterized by means of wire beam electrode, linear polarization, electrochemical impedance spectroscopy and surface corrosion morphology observation etc. The results show that after immersion for one month in seawater, barnacles are naturally attached on the steel surface. The barnacle adhesion on the carbon steel could intensify its non-uniform corrosion, in other word, the carbon steel suffered from non-uniform corrosion with lower corrosion potential by 25 mV and lower corrosion current density by 79%. After the barnacle falls off, the barrier effect of the remaining bottom shell will drop rapidly, and the corrosion rate of carbon steel will accelerate. In addition, due to the non-uniform corrosion of carbon steel caused by barnacle adhesion, the maximum potential difference of coupling is 25 mV, and the maximum galvanic current reaches 41.6 μA·cm^-2.

An electrode pairing mode based on different surface treatments of the same material is proposed in this paper to collect the asymmetric EN signal in the time domain, which might mainly reflect the local corrosion propagation kinetics of one electrode, to expand the application of the EN measurement in the pitting propagation process of stainless steel. Combining the alternant measurement of the EN and the corrosion potential of the respective electrode, the evidence of the different development of each electrode surface state during immersion was provided. The results are expected to provide a new EN measurement configuration for detecting the local corrosion propagation, and establish a transient electrochemical model corresponding to the localized corrosion on one electrode, which provides a new approach for measuring, analyzing, and predicting the local corrosion behavior of the passive engineering alloys in the seawater.

The corrosion behavior of high weathering steels with different among of Cr-Sb addition was studied via cyclic wet-dry corrosion test. The results show that the corrosion resistance is improved, but the pitting tendency increases for the steel with the Sb addition. The corrosion performance of the steel can be improved by reducing Cr while increasing Sb. However, when Cr is reduced to 3.5%, the corrosion resistance shows an inflection point, then the corrosion rate is greatly increased. Cr-Sb synergy does not change the phase composition of the rust scale of the test steel. Cu is enriched and nucleated in the rust scale and corrosion pits, and the Cu-rich phase can inhibit the inward diffusion of S into the matrix, which improves the corrosion resistance of the steel.