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The effect of coupling of copper and phosphorus in steel on atmospheric corrosion behavior was investigated using high-throughput experimental methods. Wire beam electrodes and plates with discrete distribution of composition gradients were prepared through a selective laser melting method. By combining array electrode scanning tests and EPMA, the electrochemical properties and the relationship between different copper and phosphorus contents were rapidly determined. Plenty of data obtained were analyzed according to relevant standards and screened to identify compositional ranges corresponding with the relevant compositions of existing grades of steel. To further analyze the effect of copper and phosphorus on the corrosion behavior, dry/wet cyclic corrosion test were performed using plates. A combination of XRD, FTIR, SEM, EDS, and EPMA were used to analyze the corrosion behavior. It was observed that both copper and phosphorus promoted the formation of amorphous substances, supporting the proposed mechanism by previous researchers. Furthermore, in the absence of manganese interference, copper could accumulate at the metal/rust layer interface, rendering the rust layer cation-selective and effectively inhibiting the deep penetration of chloride ions. Moving forward, we expect to develop this high-throughput experiments to investigate the coupling effects of other elements on corrosion behavior.

The corrosion resistance of ferrous alloys is greatly influenced by the presence of alloying elements, however, predicting the coupling effects of these elements remains a challenge. In the present paper, the effects of various alloying elements on the corrosion resistance of iron matrix material were investigated using high-throughput density functional theory (DFT) calculations. This work explores the dissolution behavior of metal and alloy surfaces and established correlations between calculated parameters and experimentally measurable values to predict polarization curves and simulate corrosion behavior. The results showed that doping with Cu, P, Ni, Al, Mn, Co, Si, Ti, and Zn on the Fe (110) surface can reduce the corrosion current density of the iron matrix. For Fe-Cu and Fe-Mn steels, coupling P-Ti in Fe-Cu steel and P-Si in Fe-Mn steel can significantly improve their corrosion resistance. The developed model can quantitatively predict material properties and efficiently screen compositions to design corrosion-resistant alloys.

White Etching Layer (WEL) and Brown Etching Layer (BEL) always form on the surface of rails and bearings subjected to rolling cyclic contact stress. Because of the different properties between WEL/BEL and matrix, the cracks initiate and propagate easily, leading to failure ultimately. The WEL and BEL found on pearlite rail, have been widely investigated, but WEL and BEL on bainite rail and martensite bearing have not been further studied. Especially the BEL on martensite bearing raceways has rarely been reported. This study investigates the features of WEL and BEL found on martensite bearing raceway. The BEL locates in the middle of WEL and matrix, but its hardness values are the highest, which is different from the general results reported: WEL > BEL > matrix. The WEL is mainly consisted of austenite with coarse grains, ferrite and retained tempered martensite. The mainly composition of BEL is quenched martensite. Thermal effect is the main formation mechanism of the WEL and BEL in this study. BEL forms because the surface temperature exceeds Acm point, and then rapidly decreases. The formation of WEL may originate from two processes: (1) The austenitizing and slowly cooling process again of BEL; (2) The austenitizing and slowly cooling process of the matrix. WEL and BEL forming processes are closely related to the diffusion and redistribution of carbon. The contributory heat conduction and diffusion mechanism in the confined spaces of grease lubricated bearings have been also discussed in this study.

White etching layers (WELs) and brown etching layers (BELs), formed on the upper layer of bearing raceways generally lead to surface crack initiation and propagation and significantly affect the stable operation of precision bearings. In this study, the microstructure features of WELs and BELs from two failure bearings have been characterized and analyzed. The BEL mainly consists of quenched martensite with higher hardness values. The bainite simultaneously exists at the boundary of the BEL/matrix. Owing to the relative roll and slip, temperature increases and rapid decreases are the main formation mechanisms of the BEL in this study (thermal-induced effect). The WEL can be only found on one sample, and elongated and coarse grains are found in this region. It can be speculated that the WEL may originate from the surface region temperature increasing again and then slowly decreasing. Cracks can initiate at the boundaries of the WEL/BEL/matrix. The crack propagation behaviors are significantly affected by the properties of the WEL and BEL microstructure. It is difficult for the cracks to propagate from a softer WEL into a harder BEL. Thus, the depth of cracks in the WEL is shallower. However, because of the brittle nature of quenched martensite in the BEL, cracks can easily propagate downward under contact stress. Thus, the depth of cracks can exceed 100 μm easily. The formation mechanisms of the WEL/BEL and crack propagation behaviors have been further proved and discussed in this study.

The effect of HCO3− and Cl− on the corrosion behavior of Q345 carbon steel in soil simulated solutions was investigated through electrochemical and surface characterizations. The results show that the sample behaves with active dissolution state in low concentration of Cl− solution while pseudo passivation of sample is observed in high concentration of Cl− solution. However, in solutions containing low concentration of HCO3−, the addition of high concentration Cl− does not result in the pseudo passivation of sample due to the formation of discontinuous film, which increases the corrosion rate. In addition, in solution containing high concentration of HCO3−, the addition of high concentration Cl− leads to much higher increase of corrosion rate. The deep corrosion pit is observed on the matrix due to the rapid rupture of FeCO3 film and the sufficient development of pitting.

The optimization of water chemistry in pressurized water reactor (PWR) primary circuit is one of the most effective ways to achieve both safety and economy for operating PWR nuclear power plants (NPPs). Special attention has been paid to fundamental research and engineering application of Zn-injection water chemistry (ZWC) in PWR primary circuit in recent years in China due to the rapid development of nuclear power. The present paper mainly reports the status of PWR NPPs in China and some fundamental understandings of ZWC on material corrosion. Effects of temperature (T), pH at T value, Zn concentration, Zn-injection sequence and lasting time on electrochemical corrosion behavior, oxide film characteristic and stress corrosion cracking (SCC) susceptibility of nuclear-grade austenitic alloys were investigated. A modified point defect model was used to discuss the effects of ZWC on the oxide films in high-temperature pressurized water. Some water chemistry parameters in PWR primary coolant system are proposed for mitigating corrosion and SCC of nuclear-grade austenitic alloys.

Corrosion fatigue crack growth (FCG) behavior of 316LN stainless steel was investigated in high-temperature pressurized water at different temperatures, load ratios (R = Kmax/Kmin) and rise times (tR). The environmental assisted effect on FCG rate was observed when both the R and tR exceeded their critical values. The FCG rate showed a linear relation with stress intensity factor range (ΔK) in double logarithmic coordinate. The environmental assisted effect on FCG rate depended on the ΔK and quantitative relations were proposed. Possible mechanisms of environmental assisted FCG rate under different testing conditions are also discussed.

Low cycle fatigue behaviors of SA508-3 low-alloy steel were investigated in room-temperature air, high-temperature air and in light water reactor (LWR) water environments. The fatigue mean curve and design curve for the low-alloy steel are developed based on the fatigue data in room-temperature and high-temperature air. The environmental fatigue model for low-alloy steel is developed by the environmental fatigue correction factor (Fen) methodology based on the fatigue data in LWR water environments with the consideration of effects of strain rate, temperature, and dissolved oxygen concentration on the fatigue life.

Coatings on the surface of Mg alloys are inevitably damaged during their practical applications, and corrosion can easily initiate from the damaged areas to accelerate the failure of Mg parts. A dual self-healing coating has already been developed to solve this problem in our previous work. Considering the practical application of this coating, it is necessary to investigate its service behavior in atmospheric environment. Thus, the corrosion behavior of AM60 Mg substrate with and without the self-healing coating was compared in Shenyang industrial atmospheric environment. The results show that the enrichment of sediments and rainwater on the scratch areas can accelerate the corrosion of the exposed Mg substrate. The inhibitors can be released from the damaged coating to inhibit corrosion. The dual self-healing coating shows better inhibition ability to narrow scratches due to the higher inhibitor concentration and less resumption. Also, the coating with wide scratches displays enough inhibition ability as well. The dual self-healing coating is a good alternative for Mg alloy parts in the practical applications.

The grain growth process plays an important role in the texture formation in magnesium alloys. The microstructural and micro-textural evolution of a cold-rolled Mg–Zn–Gd alloy during annealing at 350 °C for 60–190 min were tracked by quasi-in-situ electron backscatter diffraction method. The results show that grain growth takes place gradually with the annealing time increasing. Moreover, the TD-split texture maintains the texture type but alters in three aspects - the increased tilting angle, the decreased pole intensity and the widened distribution of high-intensity area. Grains with their c-axis tilting 45–70° from normal direction show preferential growth which is closely associated with the texture changes. The original grain size advantage is one of the important factors leading to the growth advantage, some grain boundaries, such as 50–60° [1¯21¯0], 50–60° [2¯75¯0], 60–70° [1¯21¯0] (∑18b), and 70–80° [101¯0] (∑10) are also considered to be related to this preferential growth.

Abstract Grain boundary (GB) oxidation of proton-irradiated 304 nuclear grade stainless steel in primary water of pressurized water reactor was investigated. The investigation was conducted by studying microstructure of the oxide and oxide precursor formed at GB on an "atom-by-atom" basis by a combination of atom-probe tomography and transmission electron microscope. The results revealed that increasing irradiation dose promoted the GB oxidation, in correspondence with a different oxide and oxide precursor formed at the GB. Correlation of the oxide and oxide precursor with the GB oxidation behavior has been discussed in detail.

Crevice corrosion behavior of Alloy 690 in high-temperature aerated chloride solution was studied using a self-designed crevice device. The SEM, EDS, XRD, and XPS analyses results indicated that the oxide films outside the crevice consisted of Ni-Cr oxides containing a small amount of hydroxides, and the oxide films on crevice mouth consisted of a (Ni,Fe)(Fe,Cr)2O4 spinel oxides outer layer and a Cr(OH)3 inner layer, and the oxide films inside the crevice consisted of a α-CrOOH outer layer and a Cr(OH)3 inner layer. When crevice corrosion occurred, the hydrolysis of Cr3+ led to the formation of Cr(OH)3 inside the crevice, and caused the pH value of crevice solution to decrease, and Cl− migrated from outside the crevice into inside the crevice due to electrical neutrality principle and accumulation. When the water chemistry inside the crevice reached the critical value of active dissolution of metal, the active dissolution of metal inside the crevice occurred. In addition, (Ni,Fe)(Fe,Cr)2O4 spinel oxides on the crevice mouth were formed by the deposition of metal ions migrated from inside the crevice. The mechanism of crevice corrosion and the formation mechanism of oxide films at different regions were also discussed.

A SnO2-doped dicalcium phosphate coating was prepared on AZ31 alloy by means of hydrothermal deposition. The results showed that the coating possessed a globular morphology with a long lamellar crystalline structure and a thickness of approximately 40 μm. The surface of the coating became smooth with an increase additive amount of the SnO2 nanoparticles. The corrosion current density and hydrogen evolution rate of the coating prepared in presence of SnO2 were reduced compared to the coating without SnO2 and the bare AZ31 substrate, indicating an improvement in the corrosion resistance of the SnO2-doped coating. Keywords: Phosphate coating, Biomaterials, Magnesium alloys, Corrosion, Stannic oxide

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

The influence of yttrium on the corrosion behavior of Mg–Y alloys has been investigated by electrochemical measurements, scanning electron microscope (SEM) observation, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analysis in NaCl solution. The corrosion resistance decreased with increasing Y content due to increasing Y-rich zone. The solid-dissolved Y improved the chemical activity of the substrate which promoted the corrosion reaction by forming Y2O3. The corrosion resistance was improved by increasing the Y concentration of matrix and proper net Y-rich structure. The sample has the best corrosion resistance when all the Y element was dissolved into the matrix of Mg–5Y in 0.1 M NaCl. Keywords: Mg–Y alloys, Corrosion behavior, Yttrium element, Solid-dissolved Y

Hydrogen evolution reaction is inevitable during the corrosion of Mg alloys. The effect of hydrogen on the corrosion behavior of the Mg–2Zn and Mg–5Zn alloys is investigated by charging hydrogen treatment. The surface morphologies of the samples after charging hydrogen were observed using a scanning electron microscopy (SEM) and the corrosion resistance was evaluated by polarization curves. It is found that there are oxide films formed on the surface of the charged hydrogen samples. The low hydrogen evolution rate is helpful to improve the corrosion resistance of Mg alloys, while the high hydrogen evolution rate can increases the defects in the films and further deteriorates their protection ability. Also, the charging hydrogen effect is greatly associated with the microstructure of Mg substrate.

A nano-ZrO2 modified coating system was prepared by incorporation of nano-ZrO2 concentrates into phenolic-epoxy resin. The corrosion performance of the coatings was evaluated in hot mixed acid solution, using electrochemical methods combined with surface characterization, and the effects of nano-ZrO2 content were specially focused on. The results showed that 1% and 3% nano-ZrO2 addition enhanced the corrosion resistance of the coatings, while 5% nano-ZrO2 addition declined it. The coating with 3% nano-ZrO2 presented the minimum amount of species diffusion, the lowest average roughness (5.94 nm), and the highest C/O ratio (4.55) and coating resistance, and it demonstrated the best corrosion performance among the coating specimens.

An analysis architecture is built to make full use of natural environment corrosion of materials data. All environmental factors, such as average temperature, average relative humidity, rainfall hours, sunshine duration, chloride ion settlement, etc., in nine atmospheric test stations, including Beijing, Wuhan, Jiangjin, and Wanning, and seawater temperature, salinity, dissolved oxygen, pH values, etc. in four marine test stations, including Qingdao, Zhoushan, Xiamen, and Yulin, are modelled monthly using a statistical analysis technique. Normal distribution, logarithmic normal distribution, Weibull distribution, and uniform distribution of the samples are checked by the Shapiro-Wilk and Kolmogorov-Smirnov methods. Subsequently, the probability distribution function, the expected population value and variance, and the confidence interval are estimated. Corrosion data for twenty-two kinds of carbon steels, low alloy steels, and stainless steels, including A3, 3C, 16Mn, 10CrMoAl, 1Cr18Ni9Ti, in atmospheric and marine test stations are analyzed. The main environmental factors for atmospheric and marine corrosion of each type of steel are determined by grey relational analysis. Subsequently, a predictive model incorporating the main corrosion environmental factors, exposure time, and corrosion rate is built by the BP artificial neural network. After the evolution of corrosion pit depth is predicted by the artificial neural network, a fracture mechanics calculation is used to evaluate the residual life of a structure with corrosion pit defects.

In this manuscript, we have developed an efficient spraying method to successfully fabricate a series of flower-like coordination polymers (CP) microparticles, including Co/BDC (1,4-benzenedicarboxylate) metal organic frameworks (MOF) and infinite coordination polymers (ICP) microparticles, as well as Ni-Co/BDC MOF and Zn/DOBDC (2,5-dioxido-1,4-benzenedicarboxylate) MOF. The spraying method has shown high efficiency and universality in synthesizing the flower-like CP. The crystalline structure can be adjusted by varying the solvent composition in the spraying process. SEM observation demonstrated the MOF and ICP microparticles possess the similar flower-like structure, which is composed of nanoflakes with smooth surface, and the flower-like microparticles could be monodisperse with as low as 5% polydispersity. Moreover, the fabrication of the flower-like CP microparticles by spraying has a wide operation window, because there is no need to precisely control the experiment conditions, like solvents, concentration, and spray order. Due to the practicality of spray technique, this work would pave the way for the manufacture of the flower-like materials and have great potential in applications of catalysis, sensor, energy storage, and so on.