The localized corrosion of 5083-H111 Al alloy in a simulated dynamic seawater zone was investigated by open circuit potential (OCP) measurement, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results revealed that, in the simulated dynamic seawater, 5083-H111 Al alloy generated visible pitting corrosion caused by the intermetallic particles (IMPs). These IMPs were composed of Al-Fe phase and Mg-Si phase, Al-Fe phase acted as a cathode during the corrosion, forming a micro-corrosion cell with the surrounding Al matrix, accelerating the corrosion of the Al matrix. Mg-Si phase was firstly acted as anode, the selective dissolution of Mg in the Mg-Si particles results in a de-alloyed outer layer on the exposed surfaces and forms Si-containing phase, then the Si-containing phase acted as cathode, prompting pitting corrosion of Al matrix. The corrosion products generated on the surface of 5083-H111 Al alloy were Al(OH)₃, Al₂O₃·6H₂O and AlCl₃. These corrosion products provided a good protection to the Al matrix in the early stage of corrosion (1-36 d), resulting in a positive shift in OCP and an increase in the polarization resistance R_p. However, in the later stage of corrosion (36-56 d), the initial corrosion products were partially detached, leading to localized corrosion again at the detachment position, resulting in a negative shift of OCP and a sharp decrease in R_p. Finally, with the prolongation of exposed time, some IMPs detached from the corrosion pits, forming corrosion cavities.

Micro-arc oxidation (MAO) surfaces were prepared on a Mg-Gd-Y-Zn-Mn alloy in four different electrolytes, namely aluminate/silicate (AS), aluminate/phosphate (AP), silicate/phosphate (SP) and aluminate/phosphate/silicate (APS), afterwards, on which films of layered dihydroxyl metal (MgAlLa) oxides (MgAlLa-LDHs) were in-situ grown to acquire the composite coating of MgAlLa-LDHs/MAOs. Then the effect of different MAO surfaces on the properties of the MgAlLa-LDHs/MAOs composite coatings were studied by means of field emission scanning electron microscopy (FE-SEM), X-ray diffractometer (XRD), energy dispersive spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS), as well as measurements of potentiodynamic polarization, electrochemical impedance and hydrogen evolution etc. in terms of their morphology, microstructure, composition and corrosion behavior in 3.5%NaCl solution. The results show that the different MAO coatings present differences in morphology, phase constituents, number of phases, element distribution and pore size, which affect the in-situ growth of the subsequent MgAlLa-LDHs nanosheets, so that the shape, size and crystallinity of the MgAlLa-LDHs nanosheets are obviously different. In addition, the composite coatings of MgAlLa-LDHs/APS-MAO show excellent corrosion resistance with a corrosion current density 9.14×10^-9 A·cm^-2, which is about four orders of magnitude lower than that of the bare Mg-alloy substrate.

Sheet-like blocking inorganic fillers are widely used in the marine anti-corrosion coating field as their high aspect ratios significantly extend the diffusion path of the corrosive medium in organic coatings. However, under the coupling action of pressure-flow of seawater in the deep sea, the weak point at the filler/resin interface in the coating often cracks due to stress concentration. To address this issue, the purpose of this article is to study the feasibility of application of the modified basalt flakes, as a filler material, to enhance the adhesion of the filler/resin interface of organic coatings. Basalt flakes were firstly chemically etched to endow with peculiar surface morphology, which afterwards were modified with a silane coupling agent to reduce their surface energy. As a result, the wettability of the modified basalt flakes to the organic resin and the interfacial bonding between the modified basalt flakes and the resin are all significantly enhanced. The failure behavior of the coating under the coupling action of pressure-flow of seawater in a simulated deep sea condition showed that the etched-modified basalt filler had a good compatibility with the resin, and the surface coupling agent molecules could participate in the curing of the coating and further increase the interfacial bonding between the coating and the filler. After corrosion test in artificial seawater by couplingaction of pressure-flow conditions for 240 h, the impedance modulus (|Z|_{0.01 Hz}) of the etched-modified basalt epoxy (EMB/E) coating was one order of magnitude higher than that of the unmodified basalt (B/E) coating. Therefore, the basalt organic coating effectively reduces the deterioration of the filler/coating interface under the coupling action of pressure-flow of seawater in simulated deep sea conditions. It can be expected to select the epoxy coating with modified basalt flakes as a candidate coating of better protective performance for engineering application in deep-sea environments.

Laser quenching technology is widely used as a means for the strengthening in the field of metallic materials. Laser quenched materials have the advantages of high precision, small heat affected zone, uniform carbide dispersion and finer grains. In order to improve the surface hardness and wear resistance of AISI 4130 steel used in petroleum field, a high hardness and high wear resistance quenching layer was prepared on the surface of AISI 4130 steel by laser quenching technology. The effect of quenching power on the microstructure evolution, corrosion resistance, microhardness and wear resistance of AISI4130 steel were investigated. AISI4130 steel samples of 10 mm×10 mm×8 mm (L×W×H) were prepared by wire cut electric discharge machine. The quenching layer was prepared on the surface of AISI 4130 steel by high power laser. The microstructure and element distribution characteristics of the steel quenched with different power was studied by scanning electron microscope (SEM) with EDS and X-ray diffractometer (XRD). The corrosion resistance of the steel before and after quenching was assessed by electrochemical workstation and immersion test. The hardness of quenched steels was measured by Vickers microhardness tester. The wear resistance of different quenched steels was tested by reciprocating friction and wear tester, while the wear scratch morphology was analyzed by three-dimensional optical microscope. After laser quenching, the surface microstructure of AISI 4130 steel was obviously refined and composed of mainly martensite and Cr-rich carbide particles. The thickness of the heat affected zone of the steels of laser quenched at 2.0 and 2.2 kW was 501.5 and 553.6 μm, respectively. The impedance arc radius of the bare AISI 4130 steel and two quenched steels may be ranked as the following: 2.2 kW quenched >2.0 kW quenched >substrate. The passive current density of the bare steel, 2.0 kW- and 2.2 kW-quenched steel was 60.00,102.28 and 108.58 μA/cm², respectively. The passivation current density of the two quenched steels was about 1.7 times that of the bare one. After quenching, the surface hardness of the steel increased by more than 85%. The average friction coefficient of the bare AISI 4130 steel and 2.0 kW- and 2.2 kW-laser quenched ones was 0.366, 0.293 and 0.195, respectively. Compared with the bare steel, the volume wear rate of 2.0 kW- and 2.2 kW-laser quenched ones was reduced by 25% and 36%, respectively. The wear resistance of quenched steels increased by 20% and 47%, respectively. The corrosion resistance of the quenched steels is reduced, but the corrosion resistance of the 2.0 kW quenched steel is better than that of the 2.2 kW ones. The precipitation of Cr-rich carbide particles in the steel will aggravate the destruction of the corrosion product film, resulting in a decrease in the corrosion resistance of the quenched steel. The higher the carbide content on the surface of the quenched steel, the more difficult it is to cut the convex surface of the abrasive into a tough phase and the wear rate of the sample surface decreases, thereby improving the overall wear resistance of the material.

In aerospace, automobile, power generation and other industrial fields, many crucial hot end components such as aviation engine, automobile engine, coal (oil, gas) boiler and turbine blades, valve components, superheater tube etc. are servicing in high temperature-, high pressure-, corrosion-environments for a long time, thus which suffered easily from surface oxidation- or corrosion-damages. The preparation of high temperature protective coating on the surface of those parts is an important technical means to improve their service performance. The mechanical bonding strength of the coating prepared by thermal spraying is not high, and the coating is usually porous. Under the condition of high temperature, corrosion is easy to occur through pores, and even penetrate the coating onto the matrix, which is not conducive to the high temperature corrosion protection of the workpiece. Laser cladding technology is an advanced and rapidly developing surface modification technology, which can make a very strong metallurgical combination for the cladding materials with the matrix, but also has the advantages of coatings with high compactness, low dilution rate, and environmentally friendly etc. This paper first summarizes the research status and achievements of high-temperature protective coatings for hot-end components in industries such as aerospace, automotive, and power generation. Secondly, it analyzes the types of defects that may occur during laser cladding for coating preparation and the cause for their formation. Finally, it points out the difficulties and challenges faced by the future development of laser cladding technology and prospects for its development direction and trend.

Through a comparative study of the corrosion characteristics, corrosion products, and electrochemical polarization of carbon steel- and stainless steel-bolt fasteners in a Cl^- containing NaCl solution, which aims to simulate offshore atmospheric environment. For carbon steel fasteners, the occurrence of rust scale can induce an extra IR drop, weakened the polarization effect of the cathodic area to the anodic crevice area, and the difference in oxygen supply led to more severe corrosion in the exposed thread area, mainly uniform corrosion. For stainless steel fasteners, the lack of oxygen in the environment led to the degradation of the passivation film performance in the thread crevice area, and the polarization effect of the exposed screw area to the thread crevice area, thus resulted in more severe corrosion in the crevice area, mainly pitting corrosion. Differentiated corrosion protection strategies were proposed for carbon steel and stainless steel fasteners in marine environments based on their distinct corrosion mechanisms.

Inclusions are inevitable metallurgical defects in steel that can significantly impact the corrosion resistance of materials by inducing local corrosion initiation. The mechanisms related with the initiation and development of inclusion-induced localized corrosion have been the subject of controversy in recent years. This paper provides a comprehensive review of the various mechanisms of inclusion-induced localized corrosion, including electrochemical corrosion, chemical dissolution, and electrochemical-chemical dissolution mechanisms. In addition, controlling the formation and behavior of inclusions is crucial for improving the corrosion resistance of steel, while the chemical composition, size and shape of the inclusions are the key influencing factors for inducing localized corrosion. Finally, the future research directions for the study of inclusions-induced local corrosion mechanism and the regulation of corrosion-resistant steel are discussed.

The superhydrophobic surface has excellent water repellency, which helps to enhance the corrosion protection performance of the coating. In this work, a superhydrophobic and corrosion-resistant nickel-based composite coating was prepared on the surface of AZ31 Mg-alloy by combining chemical deposition and electrodeposition techniques with dynamic hydrogen bubbles as a template. The microscopic morphology, structure, composition, wettability, and corrosion protection performance of the coating were characterized using scanning electron microscopy (SEM), energy spectrometry (EDS), X-ray diffractometer (XRD), Fourier infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), optical contact angle meter and electrochemical workstation. It was found that adding ZnO nanoparticles to the electrodeposition bath may change the surface morphology of the porous nickel layer and affect its hydrophobicity. The static water contact angle (WCA) tests revealed that the highest WCA value of 160.8°±2.8° was acquired for the composite coating prepared by electrodeposition in the electrolyte containing ZnO nanoparticles of 5.0 g·L^-1 and then modified by stearic acid. Compared to the bare Mg-alloy, the composite coating's corrosion potential was positively shifted by -1.23 V to -0.32 V. The corrosion current density and charge transfer resistance were reduced and increased by more than two orders of magnitude, reaching 8.41 10^-7 A·cm^-2 and 72.79 kΩ·cm² respectively, indicating the good corrosion protection ability of the composite coating to the Mg-alloy.

The impact of nitrate addition on corrosion of EH40 steel in natural seawater was investigated. The corrosion rate, morphology and products of EH40 steel, as well as the formed biofilm morphology, and microbial communities on the steel immersed in natura seawater with various addition of nitrate (0, 0.1, 1, 10, and 100 mmol/L) for 12 weeks were studied by means of mass loss measurement, potentiodynamic polarization curves, SEM, CLSM, Raman spectroscopy, and examination of high throughput sequencing of 16S rRNA gene. It was found that corrosion of EH40 steel was promoted by nitrate addition, and the promotion degree was dependent on the contents of nitrate added. Meanwhile, localized corrosion was enhanced by nitrate addition. The impact of nitrate addition on the corrosion of EH40 steel is affected by microorganisms, correspondingly, which can change the structure of microbial communities of biofilms.

Three double-layered lubricant infused surface (LIS) with different micro-nano structures (nanopores, enlarged nanopores, nanowires) on high purity Al-plates were prepared through anodizing for different times, and then filled with PAO oil. The effect of the structure of anodizing oxide films on the hydrophobicity, corrosion resistance, and stability of the prepared LISs were characterized by scanning electron microscopy (SEM), contact angle measurements, electrochemical impedance spectroscopy (EIS), and corrosion test in simulated seawater. The results showed that the |Z|_{0.01 Hz} of nanowires-LIS was still stable at 10⁸ Ω∙cm² after immersion in 1 mol/L NaCl for 240 d, showing more stable in long-term immersion corrosion test rather than the nanopores- and enlarged nanopores-LISs. Theoretical analysis showed that the nanowires-structure could store more PAO oil, and the blocking effect of its compact structure and high interaction energy with the oil greatly slow down the loss of PAO, so that the nanowires-LIS showed improved corrosion resistance and stability.

The electrochemical corrosion behavior of 3D-printed NiTi shape memory alloy in various types of artificial saliva was studied by means of open circuit potential measurement, polarization curve, electrochemical impedance spectroscopy and Mott-Schottky. The results show that with the increasing time of immersion in an artificial saliva, the open circuit potential of 3D-NiTi alloy shifted positively, while the thermodynamic stability of the alloy is improved. The alloy exhibited typical passivation characteristics, and the corrosion resistant and stable passive film might form. After Coke was added to the artificial saliva, the thermodynamic stability of the alloy decreased, the polarization curve moved to the lower left, the free-corrosion potential shifted negatively, and the corresponding corrosion current density increased. After adding 1% NaF, the thermodynamic stability of the alloy decreases sharply, showing an active corrosion state. The number of defects of the passive film increases 3.7 times, and F^- can greatly damage the integrity of the passive film.

The analysis of airworthiness standards and general specifications shows that only guiding principles such as "use magnesium alloy as little as possible" have been issued at the present for the use of Mg-alloys in airplane engines at home and abroad, but the specific restrictions that should meet, especially the protective schemes that must be adopted in marine environments, are not been clearly specified yet. In view of the insufficient data related with the corrosion performance and protection technology of Mg-alloys for airplane engines, therefore, it is difficult to effectively support the selection of Mg-alloy materials and processes, as well as the assessment of their adaptability to marine environment. In response to the problem, it is suggested to establish an equivalent environmental spectrum for laboratory accelerated testing to facilitate the evaluation of typical Mg-alloy protection processes via laboratory accelerated test, by taking the harshest corrosion environment that Mg-alloy structures may encountered during service fully into account. Meanwhile, natural environmental corrosion testing should be carried out to determine the relevant corrosion protection performance. In addition, it is necessary to acquire how the corrosion degree of Mg-alloy substrate accumulates over time when the protective coating is damaged, then make a comparison with the corrosion performance of Al-alloys in the actual service condition of aircraft engines so that to put forward the evaluation criteria of Mg-alloys. Last but not least, the corrosion performance of the coupling structures of Mg-alloy with dissimilar materials should be assessed via accelerated laboratory tests in order to verify the environmental adaptability of such typical structures.

Atmospheric corrosion is ubiquitous but varies a lot with varying climates and weather conditions at different test sites. Categorizing the atmospheric corrosivity and drawing atmospheric corrosion map with high precision remain key interest for different industries. In this study, atmospheric corrosion maps of carbon steel and galvanized steel for state gird corporation of China were constructed by inverse distance weighting (IDW) interpolation algorithm based on both the measured corrosion rates of coupons exposed at 2393 inland test stations and calculated corrosion rates from a prevalent dose-response function in 2918 sites in coastal regions. A chloride ion diffusion model in coastal region is also proposed to better predict corrosion rates of carbon steel and galvanized steel in coastal regions by using the dose response functions (DRFs) presented in ISO 9223. Cross-validation results demonstrated that the prediction accuracy of IDW interpolation algorithm of carbon steel and galvanized steel were 85.3% and 85.9%. The atmospheric corrosion maps show that the area, where C4-CX severe corrosion occurs for carbon steel and galvanized steel, accounts for 6.01% (462770 km²) and 5.25% (404250 km²) of the total area of the evaluation, respectively. The atmospheric corrosion map of the assessed area can be used to improve our capacity for corrosion protection, operation maintenance, and life prediction for outdoor engineering materials in severe corrosion area.

A series of cast Ce-containing Zn-alloys Zn-0.6Cu-0.3Ti-(0.3-0.6)Ce was prepared, and the effect of Ce addition on the microstructure and corrosion resistance of Zn-0.6Cu-0.3Ti alloy were investigated by means of X-ray diffractometer, scanning electron microscope and electrochemical corrosion test. The results showed that due to the addition of the rare earth Ce, CeZn₅ micron particles emerged in the alloys, which were distributed inside the Zn matrix or at phase boundaries, promoting the growth of the Zn matrix as dendrites and refining the Zn dendrites and secondary dendrites. Correspondingly, the free-corrosion current density of Zn-0.6Cu-0.3Ti alloy decreased rapidly from 2.76×10^-3 A/cm² to 5.85×10^-4 A/cm² after the doping of 0.3% Ce. The effect of Ce content on the corrosion properties of Zn-Cu-Ti-Ce alloy becomes weaker as the corrosion time increases. The impedance spectra of the alloy containing Ce has only one capacitive arc, in the early stage of corrosion, the influence of Ce content on the radius of the capacitive arc is small, with the extension of corrosion time, the influence of Ce becomes more and more obvious, and the overall trend is increasing.

In order to improve the service performance of traditional zirconia-based ceramic coatings in high-temperature and high-pressure environment, the novel thermal barrier coatings based on Y₂O₃/Gd₂O₃/Yb₂O₃ co-doped ZrO₂ top layer (YGYZ), Y₂O₃/Eu₂O₃ co-doped ZrO₂ middle layer and NiCoCrAlYTa bonding layer were prepared, whose YGYZ top layers were doped with 10%, 20%, and 30% MoSi₂ self-healing particles, respectively. Then their microstructure, chemical composition, phase constitution and isothermal oxidation resistance at 1100 ^oC in air were assessed by means of scanning electron microscope (SEM), X-ray diffractometer (XRD), X-ray energy dispersive spectrometer (EDS) and box muffle furnace. The results show that the cross-sectional morphologies of the coatings doped MoSi₂ self-healing particleswere layered structures, and their phase structures would not change with the variation of the doping amount of MoSi₂, they were all composed of t-ZrO₂ and t-MoSi₂. Among them, the coating with a top layer doped 20% MoSi₂ exhibited the best high temperature performance, whose weight gain was 3.7 mg/cm² after 200 h constant temperature oxidation at 1100 ^oC, which decreased by 5% and 18%, respectively, compared to coatings with 10% and 30% MoSi₂.

Owing to the urgent need of aviation industry for microbial control of the fuel system of aircraft, it is imperative to establish a safe and efficient microbial control strategy for the fuel system to ensure the safe operation of aircraft. Water is generally considered to be an undesirable substance in the fuel system, which may lead to microbial contamination. The novel antibacterial strategies that can turn water into things of value with high disinfection efficiency have been urgently needed for the fuel system. This review surveys the edged technologies which may provide the design principle and important experimental guidance of "active" antibacterial functional coating. Accordingly, two electron sources include the extracellular electron transfer and the galvanic corrosion on the coated metals may become the key to spontaneous microbial-control coating.

In the early stage of crevice corrosion, the change of micro-chemical environment inside the crevice are closely related to the occurrence and development of crevice corrosion. This work briefly introduced the basic principles and influencing factors of crevice corrosion. Then the research progress in monitoring the ion concentration variation inside the crevice during recent years were summarized, including the in situ chemical imaging of solid-state ion-selective electrodes and fluorescence molecular in situ monitoring method, sampling analysis method and numerical calculation simulation. In addition, research work of micro-electrochemical sensors combined with SECM in the measurement of the ion concentration variation of micro-areas inside the crevice of stainless steel by our group is also introduced. Future applications of this technique in crevice corrosion are highlighted.

The free corrosion potential and galvanic corrosion current of different spots of an inclined pipeline were assessed via a home-made device, aiming to simulate the CO₂ induced localized-corrosion emerged at the area with standing water of an inclined pipeline of X70 steel for transporting wet gas, with an electrode composed with a bundle of isolated wires of matrix-like distribution as measuring electrodes. So that to illustrate the relevant localized corrosion mechanism. The results showed that localized corrosion happens for different pipeline structure by different gas flow conditions. What is more, the localized corrosion became more concentrated when the exposure time was elongated. The most severe localized corrosion was seen when the gas flow velocity was 2 m/s and the pipeline had an inclined angle of 30°. Amongst the three factors, including the extent of non-uniformity of water film thickness, frequency of waves arisen by the high velocity gas flow and the formation of corrosion film, that affected the corrosion process, wave frequency and corrosion film had the most influential effect.

To improve breadth and depth of corrosion theory for metal materials, a combined technique of electrochemical-inductively coupled plasma atomic emission spectrometry (ICP-OES) was developed in recent years. In this technique, an inductively coupled plasma atomic emission spectrometer was coupled to the downstream of a home-built electrochemical flow cell to track the concentration transient of the corrosion products dissolved in the corrosion medium, so that the elemental dissolution rates of metal electrode could be determined in real time. The working principles and the development of this technology were introduced briefly and the applications of this technology in metal corrosion research were summarized at present. Finally, the existing problems and future directions for development of this technique were pointed out.

Abradable seal coatings is widely used in the field of aerospace industry, since it can improve the efficiency of the aero-engine. Due to its special structure and composition, abradable seal coatings would face severe corrosion failure problems. Therefore, the phase-selective dissolution reaction in the early stage of corrosion of the CuAl-NiC abradable seal coating in NaCl solution is simulated by means of finite element method (FEM). Morphology characterization and electrochemical test were conducted to determine the geometric dimensions and boundary conditions required for FEM. The FE simulation was then carried out, while the modeling results were compared with the free-corrosion potential of the coating measured by the polarization curve, and the dissolution results of the ICP-OES test to verify the reliability of the established model. Furthermore, by inputting the composition ratio and the electrochemical properties of substances of a newly designed coating into the established model, its corrosion resistance can be acquired, which will provide some insights for the design of abradable seal coatings.

A stable solid slippery surface (SSS) was fabricated by constructing micro-nano structure on the surface of low carbon steel via electrodeposition method and then lubricant was infused. The corrosion behavior of SSS and the changes of surface morphology and composition after corrosion test under liquid films of different thicknesses (500, 250, 100 and 50 μm) was characterized by means of electrochemical tests, scanning electron microscopy (SEM) and X-ray diffractometer (XRD) etc. The results showed that in the early stage of thin liquid film corrosion, as the thickness of the thin liquid film decreases, the corrosion behavior of SSS shows small differences, and the SSS showed the largest corrosion resistance when the thickness of thin liquid film was 100 μm. After immersion for 1 d, the limited diffusion current density is 4.899×10^-6 A·cm^-2 (at -1.4 V), and the fitted impedance value reaches 1.54×10⁵ Ω·cm². Even after soaking for 7 d, it still exhibited an impedance value of 6.98×10⁴ Ω·cm², and it was hard to detect the formation of corrosion products, demonstrated its excellent stability and corrosion resistance.

At present, cathodic protection technology is the most effective and economical method for preventing oil and gas storage tank from corrosion, while regional cathodic protection technology, especially the regional cathodic protection technology of tank farms, is not mature enough. How to determine whether the cathodic protection applied to the protected facility is achieved the desire effect is still the bottleneck of the current technological development. This paper primarily summarizes the research on cathodic protection of tank floors from the previous decades and the direct and indirect factors impacting the tank outer floor corrosion, introduces the mechanisms, methods and forms of anode bed used for cathodic protection of tank floors, describes the application of the current numerical simulation calculation methods in cathodic protection of tank floors and the latest advancements. Finally, we summarize the existing drawbacks of numerical simulation techniques for cathodic protection and forecast their future development trends, with the goal of providing a helpful reference for construction of cathodic protection systems.

The oxidation behavior of 9Ni steel slab at 900~1250 ℃ were investigated by employing a combined thermal analysis and mass spectrometer system, field emission scanning electron microscopy (FE-SEM), field emission electron probe microscopy (FE-EPMA), X-ray diffractometer (XRD) and soft wear FactSage10.0. The results show that the constant temperature oxidation of 9Ni steel at 900-1250 ℃ mainly follows the parabolic law, and the oxidation rate is controlled by the diffusion of metallic ions in the oxide layer, Ni exists in the oxide layer in the form of FeNi₃ and NiFe₂O₄ in the inner layer, and elemental Ni enriched at the boundary of the inner/outer layers of the formed oxide scale, and intertangled with Fe-oxides, The high temperature corrosion at grain boundaries of 9Ni steel billet should be attributed to Fe₂SiO₄ (ferrosilicon olivine) which come from the combining of SiO₂ generated by Si oxidation and FeO of the product of iron oxidation, When the temperature is higher than the eutectic temperature (about 1170 ℃), ferrosilicon olivine will be irregularly permeated into austenite grain boundaries in the matrix as liquid.

A novel enamel coating was prepared on 20 steel, then the oxidation and NaCl deposit induced corrosion of the steel without and with enamel coating were studied in air at 400 ℃ for 1000 and 200 h respectively. It is revealed that the prepared enamel coating is compact, amorphous, and can be well combined with the substrate. There are no cracks and spallation of enamel coatings was observed after corrosion tests. The enamel coating has high thermal stability and corrosion resistance, which provides effective protection for the 20 steel substrate.

Electroplating silver is carried out in an alkaline DMH plating bath with 5,5-dimethylhydantoin (DMH) as complexing agent. The cathodic reduction process of silver from alkaline DMH plating bath is analyzed by chronopotentiometry, cathodic polarization curve and electrochemical impedance spectroscopy (EIS), meanwhile, the nucleation/growth mechanism of silver are also studied by cyclic voltammetry and chronoamperometry, finally the electrodeposition behavior of silver in alkaline DMH complex system is comprehensively discussed. The results show that the main form of silver complex ions in the alkaline DMH plating system is [Ag(C₅H₇N₂O₂)₂]^-, which is converted to [Ag(C₅H₇N₂O₂)] through a preceding reaction and discharged directly on the cathode. The electrodeposition process of silver in this system is an irreversible electrode reaction controlled by diffusion step. Besides, the electrodeposition of silver undergoes a nucleation process and follows a three-dimensional transient nucleation mechanism.

A new type of Si-Zr composite conversion film was prepared on the surface of ADC12 aluminum alloy by chemical conversion method. The content of aminobissilane was optimized based on the results of copper sulfate dropping test and polarization curve measurement. The microstructure, chemical composition and crystallographic structure of the conversion film were characterized by means of field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR). The corrosion resistance of the passive film was studied by electrochemical test and neutral salt spray test. The results show that the introduction of aminobissilane can significantly improve the uniformity and compactness of the conversion film; thus aminobissilane greatly improves the corrosion resistance of conversion films; among others, the corrosion resistance of the conversion film with 60% aminobissilane is the best. Compared with the Zr conversion film, the capacitive reactance radius and the low frequency impedance value of the Si-Zr composite conversion film increase by more than 3 times respectively, and in consequence, the life-time of salt spray corrosion resistance increases by more than 20 times.

The passivity of type 304 stainless steel in aqueous solution at different pH values has been assessed, and the acquired data suggest that the passive film formed on type 304 SS is n-type semiconducting, and the donor density within the passive film is inversely proportional to the applied voltage except those in pH=13.4 solution. The current density in steady-state is voltage-independent in the passive range, while the thickness of the barrier layer has a linear relationship with the applied voltage, which are satisfied with the statements of the point defect model (PDM). EIS data are analyzed with the PDM by optimizing the model on the data using genetic algorithm approach. In addition, the impedance data over the entire passive range can be described by the fitted parameters, which can be utilized to predict the corrosion evolution of the sample as a function of time. The results of the optimization indicate that interstitial cations are the dominant defects in the barrier layer and that the diffusivity of the defect is about 10^-19 cm²·s^-1.

Based on the principle that the amine group in the synthesized organosiloxane-modified cationic acrylic (SMCWA) latex can cure epoxy resin, the corrosion-resistant epoxy resin/SMCWA latex composite coating were prepared on the surface of carbon steel plate. The SMCWA latex was characterized by laser nanometer particle size analyzer. The structure and morphology of the composite coatings were analyzed by FT-IR and SEM. The corrosion resistance of the composite coating was studied by copper sulfate spot test, electrochemical test and neutral salt spray test. The results show that the synthesized stable SMCWA latex has small particle size and uniform particle size distribution. Compared with the blank SMCWA latex coating, the compactness and corrosion resistance of the epoxy resin/SMCWA latex composite coating have been greatly enhanced. When the composite coating prepared with the mass ratio of epoxy resin to SMCWA is 9.5/0.5, as a result, the life-time of copper sulfate corrosion resistance is increased by 116 s; the AC impedance is increased by 4 times, and the corrosion current density is decreased by an order of magnitude in 3.5%NaCl; and the neutral salt spray resistance is also greatly enhanced for the prepared composite coating.