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Purpose: This paper aims to study the effect of Hg2+ on the corrosion behavior of Al–2%Zn coatings on AA5083 in 3.5 Wt.% NaCl solution. Design/methodology/approach: Potentiodynamic polarization and electrochemical impedance spectroscopy are used to investigate the effect of Hg2+ on the corrosion behavior. The surface and cross-sectional morphology are characterized by scanning electron microscopy and energy dispersive spectroscopy (EDS) to further reveal the corrosion mechanism of Hg2+. Findings: The results show that the corrosion behavior of the coating changes significantly as the concentration of Hg2+ increases from 5 to 30 μg/L. The corrosion production film can inhibit the corrosion process when Hg2+ concentration is in the range of 0.5–5 μg/L, while Hg2+ can promote the corrosion process significantly when its concentration reaches to 30 μg/L. The generation rate of dense oxide film on the coating surface is faster than dissolution rate when the concentration of Hg2+ is in the range of 0–5 μg/L, which makes the coating "self-healing" and thus slightly slows down the corrosion rate. The EDS analysis shows that excessive Hg2+ are preferentially deposited at locations with inhomogeneous electrochemical properties, which in turn accelerates corrosion. Originality/value: The corrosion resistance of Al-based coatings is significantly affected by Hg2+ in seawater. Thus, it is important to explain the corrosion mechanism of Al–2%Zn coatings under the combined effect of Hg2+ and Cl− in 3.5 Wt.% NaCl solution. [ABSTRACT FROM AUTHOR]

Laser surface quenching technology was used to modify the surface microstructure of as-cast Ni-Al bronze (NAB). The modified microstructure was studied by scanning electron microscopy (SEM), and the effect of laser process parameters on microstructure evolution was investigated. It was found that a fine-grained zone with fully β phase microstructure formed on the surface of NAB. The depth of the fine-grained zone increased with the increase of laser power, and surface melting occurred when the power reached a threshold value. Laser scanning at a low rate caused the coarsening of grain boundary, while too high rate led to incomplete quenching. Spot overlap ratio determined the microstructure of the superimposed area, and unsuitable ratio would cause bulky κ precipitation at the grain boundary or incomplete transformation from α phase to β phase. [ABSTRACT FROM AUTHOR]

The microstructures of AA4045/AA3003Mod./AA4045 aluminum-brazed sheet were observed and determined by stereoscopic digital microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive spectrometer (EDS). The corrosion process of the brazed sheet in the exfoliation corrosion (EXCO) solution was investigated by electrochemical impedance spectroscopy (EIS) and electrochemical noise (EN) techniques. The results showed that the brazed sheet was composed of the Al-Si eutectic zone, the precipitates-free zone (PFZ), the band of dense precipitates zone (BDP) and the core material. With the immersion time increased, the capacitive time constant in EIS plot changed from one time constant through two unclear time constants to two clear time constants, and then went back to two unclear time constants again. The maximum relative energy in energy distribution plot (EDP) changed from small scales through middle scales to large scales, and then went back to middle scales. The corrosion process could be divided into four stages: the dissolution of the eutectic α -Al in the resolidified clad in the form of pitting corrosion; the corrosion of the primary α -Al grain boundaries in the form of intergranular corrosion (IGC); the corrosion of the BDP zone in the form of exfoliation corrosion; and the corrosion of the core material in the form of IGC. [ABSTRACT FROM AUTHOR]

Abstract: A steel corrosion sensor based on fibre Bragg gratings (FBGs) has been developed and tested in this paper. The steel corrosion sensor has been formed by electroplating a Fe–C film on a metallized FBG. The coated FBG sensors have been tested in cabinets in which the availability of chloride ions and oxygen are controlled. The microstructural changes have been investigated by optical microscopy and SEM imaging. The FBG spectra are collected by a spectrometer. The results show that the spectra change, the wavelength shift, and the occurrence of multiple peaks are related to the corrosion degree of the Fe–C film. [Copyright &y& Elsevier]

ZnAlCe layered double hydroxides intercalated with 1-hydroxyethylidene-1, 1-diphosphonic acid (HEDP) were synthesized by the co-precipitation method. The surface morphology and structure of ZnAlCe-HEDP LDHs were observed and determined by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy. The inhibition behavior and mechanism of ZnAlCe-HEDP LDHs for Q235 steel in 3.5% NaCl solution was measured by weight loss, inductively coupled plasma mass spectrometer (ICP-MS), polarization curves, electrochemical impedance spectroscopy (EIS), energy dispersion spectrum (EDS) and X-ray photoelectron spectroscopy (XPS). The results show that the HEDP anion is successfully intercalated into ZnAlCe LDHs interlayer and the synthetic ZnAlCe-HEDP LDHs has a lamellar morphology with well-defined crystalline structure and a basal plane spacing 1.056nm. Compared with ZnAl-NO 3 LDHs and ZnAl-HEDP LDHs, ZnAlCe-HEDP LDHs has a better inhibition effect on Q235 steel in 3.5% NaCl solution. The higher inhibition effect of ZnAlCe-HEDP LDHs is related the reduction of chloride ions in solution by ion exchange effect between HEDP ions and chloride ions, and the formation of inhibition film on steel surface by the ferrous-HEDP chelates and zinc, aluminum and cerium hydroxides. [ABSTRACT FROM AUTHOR]

• The effect of bending deformation on the corrosion behavior is discussed from the microstructure evolution and stress distribution. • Bending deformation causes stress concentration on both sides of the cross-sectional samples. • Discontinuous Si particles in non-brazed samples are unfavorable to the development of intergranular corrosion. • Si "needles" in brazed samples provide effective propagation path for intergranular corrosion. This study provides an insight into the effect of bending deformation on the corrosion behavior of non-brazed and brazed AA4343/AA4047/AA3003/AA4047/AA4343 composite sheet from the rolling direction (RD) and the transverse direction (TD) cross sections, by combining electrochemical measurements, scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) techniques. Grain size had a greater effect on the corrosion resistance, as compared with the textures. Localized corrosion initiated from intermetallic particles (IMPs) for both non-brazed and brazed samples whether bending or not. After bending deformation, stress concentrations at the outer layer were found in non-brazed and brazed samples. For non-brazed samples, bending deformation had little effect on the corrosion behavior due to the absence of intergranular corrosion (IGC). For brazed samples, Si "needles" provided effective corrosion propagation path, leading to a reduction of corrosion resistance. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, the influence of different aging temperatures on the tensile ductility and Intergranular Corrosion (IGC) performance was investigated by using SEM, TEM, U2-net, DL-EPR, and EIS. The U2-net was employed for efficient and accurate identification of the Laves phase in the alloy 625. In parallel, an extensive analysis was conducted to assess the influence of Laves phase precipitation on the tensile ductility of the alloy. Additionally, an investigation into the precipitated phase was undertaken to explore the correlation between tensile ductility and IGC. The research findings indicate that with increasing aging temperature (from 873 K to 993 K), the elongation initially slightly increases, then sharply decreases, and finally slightly increases again. Simultaneously, the sensitivity to Intergranular Corrosion first increases and then slightly decreases. Additionally, the trained U2-Net achieved an average accuracy rate of 99.3% on the validation dataset, demonstrating that deep learning networks can effectively and rapidly identify Laves phases in SEM images. DL-EPR results reveal a certain correlation between high Ra values and low elongation. [Display omitted] • Innovative use of U2-net for efficient Laves phase identification in 625 alloy. • Quantitative study on Laves impact: model modifications reduce errors in assessing tensile toughness for 625 alloy. • DL-EPR reveals: low 625 alloy tensile toughness corresponds to high intergranular corrosion susceptibility. [ABSTRACT FROM AUTHOR]

Multi-layered aluminium sheets are quickly gaining wide applications in several industries. However, a complete understanding of how the macro- and microstructures of composite influence the corrosion behavior is still far from being achieved. In this work, the electrochemical behavior of a 4343/3003/7072 aluminum alloy (AA) composite in 3.5 wt.% NaCl solution was investigated using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and scanning electron microscopy (SEM). The evolution of corrosion morphologies was analyzed from cross-sectional and plane directions, and the localized corrosion mechanism was discussed. Due to the galvanic effect existed in the cross-section, the corrosion resistance of the cross-section was higher than that of the plane surface. From the cross-section, the AA3003 was protected as the cathode and the adjacent AA4343 and AA7072 acted as anodes. Localized corrosion mainly initiated around Al-Si-Mn-Fe and Si-rich phases. [ABSTRACT FROM AUTHOR]

The effect of wetting time on localized corrosion of AA5083-H111 aluminum alloy in a dynamic seawater/air interface zone was investigated using electrochemical measurements, scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. Longer wetting time resulted in a more serious localized corrosion degree and thus led to an uneven and incomplete corrosion product film. This was attributed to the presence of a thin electrolyte layer upon the alloy, restricting the repassivation of the corrosion pits. • The effect of wetting time on localized corrosion AA5083 Al alloy in a dynamic seawater/air interface zone was investigated. • A longer wetting time resulted in a more incomplete and uneven corrosion product film. • The presence of a thin electrolyte layer formed on the alloy and obstructed the diffusion of oxygen to the Al alloy surface. [ABSTRACT FROM AUTHOR]

The nickel-ferric layered double hydroxides (NiFe-LDHs) film which are commonly used as catalysts was fabricated on Q235 steel in-situ via two-step hydrothermal method. And the superhydrophobic NiFe-LDH-PFDTES film was obtained by 1 H, 1 H, 2 H, 2 H-perfluorodecyltriethoxysilane (PFDTES) modification. To a certain extent, the application of NiFe-LDHs has been broadened. The structure and composition of NiFe-LDHs film and NiFe-LDH-PFDTES film were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectrometer (EDS), and Fourier transform infrared (FT-IR). The wettability of films was analyzed by water contact angle testing. And the corrosion resistance of NiFe-LDHs and NiFe-LDH-PFDTES film in 3.5 wt% NaCl solution were measured by using potentiodynamic polarization curve and electrochemical impedance spectroscopy (EIS) techniques. The results show that NiFe-LDHs and NiFe-LDH-PFDTES film were successfully prepared on the surface of Q235 steel. By adjusting the preparation conditions, the NiFe-LDH-PFDTES film with optimal corrosion resistance was prepared in the condition containing the hydrothermal solution concentration is 1 unit and hydrothermal time for 6 h. The hydrophobicity changes little with the hydrothermal parameters, and all reach the state of superhydrophobic, the contact angle is greater than 150°, the sliding angle is less than 1°. For the superhydrophobic film, NiFe-LDHs has excellent synergy with PFDTES, covering of an "air film" on the rough structure of LDHs, blocking the solution from contact with the substrate, thereby providing corrosion resistance. NiFe-LDH-PFDTES film exhibits much better corrosion protective performance than NiFe-LDHs film in 3.5 wt% NaCl solution, the impedance modulus is increased about 4–5 orders of magnitude compared with Q235 steel, and the highest protection efficiency can reach 99.99%. [Display omitted] [ABSTRACT FROM AUTHOR]

ZnAlCe layered double hydroxide intercalated by molybdate (ZnAlCe MoO 4 LDH) was successfully synthesized by using co-precipitation method, and the morphology, structure of ZnAlCe MoO 4 LDH were observed and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) techniques. The inhibition behavior of ZnAlCe MoO 4 LDH for Q235 steel in 3.5%NaCl solution was determined by polarization curves, electrochemical impedance spectroscopy (EIS), inductively coupled plasma mass spectrometer (ICP-MS) and X-ray photoelectron spectrometer (XPS) methods. The results shows that the synthesized ZnAlCe MoO 4 LDH has a lamellar structure with a particle size of 0.1–2.0 μm, an average thickness of 30 nm, and a basal plane spacing of 0.898 nm. Compared with the addition of ZnAl layered double hydroxide intercalated by nitrate (ZnAl NO 3 LDH) and ZnAl layered double hydroxide intercalated by molybdate (ZnAl MoO 4 LDH) in 3.5% NaCl solution, Q235 steel in 3.5%NaCl + ZnAlCe MoO 4 LDH solution has a lower corrosion current density, larger polarization resistance and a higher inhibition efficiency. The addition of ZnAlCe MoO 4 LDH will reduce the chloride concentration in 3.5% NaCl solution by the anion exchanged with molybdate, and improve the corrosion resistance of Q235 steel owing to the formation of passive film with the composition of ferrous or iron molybdate and deposition film with zinc and cerium hydroxides. [ABSTRACT FROM AUTHOR]

Abstract: The platinum (Pt) particle electrocatalysts supported on the indium tin oxide (ITO) substrate were prepared by the pulsed electrodeposition for the methanol oxidation. The effect of the lower potential pulse duration (t l) of the electrodeposition on the surface morphology and structure of the Pt particles was investigated by the X-ray diffraction and scanning electron microscopy. The amount of the Pt loading was determined by an inductively coupled plasma method, and the electrocatalytic activity of the prepared Pt electrocatalysts on the ITO for the methanol oxidation was characterized by cyclic voltammetry. The results showed that the t l has a significant influence on the surface morphology of the Pt particles on the ITO substrate. As the t l decreases from 1 to 0.01s, the deposited Pt particles on the ITO exhibit flower-, nanosheet-, prickly and smooth spherical-like morphology in turn. Furthermore, there is a remarkable effect of the surface morphology of the Pt particles on the electrocatalytic activity for the methanol oxidation. Among all these morphologies, the flower- and nanosheet-like Pt particles on the ITO have a much higher mass specific activity (MA) for the methanol oxidation, and the Pt particles with prickly surface followed while the smooth spherical Pt particles have the lowest MA. In particular, the dispersed Pt nanosheets prepared at t l of 0.5s has the highest MA. The much improved MA of the dispersed Pt nanosheets is attributed not only to the large electrochemically active surface area (ECSA) achieved, but also to the high electrocatalytic activity per unit ECSA related to its special morphology. [Copyright &y& Elsevier]

Abstract: The relationship between surface functional groups and electrochemical behaviors of polyacrylonitrile (PAN)-based carbon fibers (CFs) differentiated by oxidation treatment in air was studied. The chemical character of the CFs surface was estimated by X-ray photoelectron spectroscopy (XPS) and the electrochemical behavior of treated CFs in CuSO4 plating solution was studied by electrochemical setup. The influence of functional groups on the morphology of copper deposits was characterized by field-emission scanning electron microscopy (FESEM). It was found that the O/C atomic ratio rose rapidly from 23.05% (as-received carbon fibers) to 42.83% as the oxidation temperature was increased to 400°C and the content of –C highest. Concentrations and types of the functional groups on CFs surface showed a close connection with the electrochemical response of CFs in CuSO4 plating bath. It was showed that Cu electrodeposition was the interaction of applied voltage and the reduction of surface functional groups. With the functional groups increased, the quantities of the Cu nuclei increased, further the morphology of deposited Cu was affected. [Copyright &y& Elsevier]

Abstract: The friction and wear properties of short carbon fibers (SCFs) reinforced aluminum matrix composite were studied. The influences of the fiber volume fraction, load applied, rotating speed, and wear mechanism were discussed. The results indicated that SCFs/Al composite had better tribological properties than Al alloy. The friction coefficient and wear mass loss decreased with the fiber volume fraction increased, but increased as the load and rotating speed increased, respectively. SCF reduced direct contact between the matrix and counterpart and improved the wear resistance of SCFs/Al composite greatly. The wear displayed a linear evolution in all the range of load. Surfaces before and after wear tests were characterized using scanning electron microscopy (SEM) and energy-dispersive analysis of X-ray (EDAX) spectroscopy. [Copyright &y& Elsevier]

Abstract: The tribological behaviour and wear mechanism of Ni–P–Gr (graphite)–SiC (manufactured by electroless plating) is surveyed in this paper. The worn surface, wear debris and the compositional changes that take place during wear were characterized using scanning electron microscopy (SEM) and energy-dispersive analysis of X-ray (EDAX). By comparison with Ni–P–Gr and Ni–P–SiC, the results indicate that hybrid Ni–P–Gr–SiC composite presented well anti-friction and wear resistance which is resulted from a graphite-rich mechanical mixed layer (GRMML) formed on the contact surface. Hard SiC particles mixed with GRMML played a load-bearing role at high load when relative motion occurs. After heat treatment at 400°C for 1h, the wear rate of the hybrid composite decreased with an increase in microhardness. During sliding, the temperature of the hybrid composite occured less change than Ni–P–SiC coating and further guaranteed the stable state of the whole wear process. [Copyright &y& Elsevier]

Abstract: In this paper, the friction behaviour and wear mechanism of electroless Ni–P matrix with PTFE and/or SiC particles composite coating are investigated by virtue of ring-on-disk wear machine at a high load of 150N. The worn surface, wear debris and the composition changes after wear were characterized using scanning electron microscopy (SEM) and energy-dispersive analysis of X-ray (EDAX). By comparison with Ni–P and Ni–P–SiC coatings, the results indicated that the combination of a PTFE-rich mechanical mixed layer (PRMML) formed on the worn surface and hard SiC were responsible for the good tribological properties of the hybrid Ni–P–PTFE–SiC composites at high load. After heat treatment at 400°C for 1h, the wear rate of Ni–P matrix composites decreased with corresponding increase in microhardness. During sliding, an obvious decrease in the temperature rise with PTFE addition was attributed to the good anti-friction of PTFE. [Copyright &y& Elsevier]

Abstract: A facile method to fabricate submicrometer-sized hollow nickel spheres by autocatalyzing the redox reaction around a sacrificial colloidal particle surface is presented in this paper. The size distribution of these spheres can be controlled by regulating the concentration of the alkali solution. The hollow nickel particles were characterized by field emission scanning electron microscopy, transmission electron microscopy and X-ray powder diffraction. The hollow spheres produced by this process may have potential applications in many fields, including chemistry, biotechnology and materials science. [Copyright &y& Elsevier]