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The formation and corrosion processes of a conversion film on the AZ80 Mg alloy with different second phases were compared to clarify the effect of microstructure on the quality of protective coatings.

The size and distribution of second phases in the edge and central regions of the AZ80 cast ingot exhibit a great difference. The film growth processes and their corrosion resistance on the edge and central regions of the AZ80 cast ingot were investigated by scanning electron microscope observations, immersion tests and electrochemical measurements.

The results indicate that second phases act as micro-cathodes and hydrogen evolution reaction occurs on their surface, which is not beneficial for the deposition of the conversion film.

The conversion film formed on the central regions of AZ80 cast ingot with a low volume fraction of second phases exhibits a more uniform surface and higher corrosion resistance than that formed on the edge regions of the sample with a higher volume fraction of second phases.

Magnesium alloys, although valuable, are reactive and require protection before its application in many fields. The purpose of this study was to evaluate a novel anticorrosive chemical conversion film on AZ80 magnesium alloy by environmental-friendly calcium series surface pretreatment.

The corrosion resistance of the film was evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy in 3.5 Wt.% NaCl solution. The surface morphologies, microstructure and composition of the film were investigated by scanning electron microscopy and energy-dispersive spectroscopy.

The corrosion current density of the calcium series film decreased by more than one order of magnitude as compared to that of the AZ80 magnesium alloy. The conversion film presented dry-mud morphology, and its thickness was estimated to be approximately 4 μm. The conversion film was highly hydrophilic, and the organic coating adhesion on treated AZ80 surface was approximately 13.5 MPa.

Excellent performance of the calcium-based chemical conversion film on Mg alloy was obtained, which does not contain heavy metals or fluorides and completely conforms to European RoHS (Restriction of Hazardous Substances) standard.

This paper aims to investigate the effects of different electrolyte systems on the properties of micro-arc oxidation coating on 7050 high strength aluminum alloy.

The coatings were prepared in silicate system with Na₂SiO₃ as main component, borate system with Na2B4O7 as main component and aluminate solution with Na₂AlO₂ as main salt, respectively.

The results show that the 7050 high strength aluminum alloy shows the best properties in silicate system.

This manuscript studied the crucial influence of different electrolyte systems on the microstructure and properties of the aluminum alloy micro-arc oxidation layer.

This paper aims to consolidate the results of various researchers focusing the different applications, so that this paper could become the torch bearer for the futuristic researchers working in the domain of cold gas dynamics spray coating.

A study on the cold spray coating is presented by summarizing the data present in literature. Important factors such as coating temperature, pressure, coating thickness, particle size, which affect the erosion-corrosion (E-C) resistance, physical and mechanical properties of boiler steel are stated. This paper also addresses the use of cold spray coating and compares it with other different thermal spray processes.

From the literature review, it was noticed that cold spray technology is best as compare to other thermal spray processes to reduce porosity, increase hardness, adhesion strength and retention in properties of feedstock powders.

Cold spray coating technology has a great potential in almost every field especially in restoration of surfaces, generation of complex surface, biomedical application, resist hot corrosion, wear, oxidation and erosion corrosion.

This paper aims to overcome the corrosion in AA7075 by incorporating the dual-reinforcements like Al2O3 and SiC through friction stir processing (FSP). In recent days, an automotive monocoque structure undergoes corrosion because of changes in environmental conditions.

Surface hybrid composites (SHCs) of AA7075 with different weight ratios of Al₂O₃ and SiC were fabricated at a rotating speed of 1000 rpm, traveling speed of 56 mm/min and tool tilt angle of 2º with two passes. Surface regions were observed using optical microscopy, and the potentiodynamic corrosion test was performed under a 3.5 per cent NaCl environment at room temperature. Then, the surface morphology analysis of corroded samples and their structural properties were also investigated through scanning electron microscopy (SEM), X-ray diffraction (XRD) and electron dispersive spectroscopy (EDS).

Through FSP, an improved interface between the reinforced particles and the AA7075 base matrix was observed because of the severe plastic deformation. Potentiodynamic polarization tests confirmed that the AA7075 matrix with a higher concentration of Al₂O₃ and a lower concentration of SiC (Al₂O₃ – 75 per cent and SiC – 25 per cent) possesses a lower corrosion rate than other specimens. This result is because of the combined effect of stable passive film formation and the resistance produced by hard SiC particles. In addition, the formation of a stronger interface between the reinforcements and the base matrix impedes the NaCl solution attack. The SEM micrograph depicts the film crystallinity variations with an increase in Al₂O₃ content. Debonding between the layers was observed on increasing the SiC content in the base matrix. XRD shows the peaks of reinforcing elements that influence the corrosion behavior. These observations suggest that the AA7075 reinforced with a higher concentration of Al₂O₃ and a lower concentration of SiC through FSP affords a suitable solution for automotive monocoque applications.

The corrosion rate has been identified for AA7075 SHCs with various concentrations of Al₂O₃ and SiC and has been compared with that of the base metal and the friction stir processed specimen without reinforcement.

This paper aims to investigate the corrosion evolution process of AZ91 magnesium alloy in 3.5 wt.% NaCl solution under different stresses by using in situ methods, thereby evaluate the influence of stress on the corrosion sensitivity of AZ91 magnesium alloy, and discuss the potential mechanism.

A four-point bending method was used to apply different loads to the magnesium alloy samples, a charge coupled device camera and electrochemical impedance spectroscopy test being used for in situ study. Scanning electron microscopy and X-ray diffraction (XRD) analysis were performed for corrosion product and morphology characteristics.

The observation results show that the corrosion of AZ91 magnesium alloy becomes more and more serious with the increase in the stress and generated many corrosion products. Originally, corrosion products prevented alloy matrix from contacting the corrosive medium. However, the increase in the stress facilitated the emergence of the corrosion holes in the corrosion products, which provided the microscopic channels for corrosive solution to attack the Mg alloy matrix, and accelerated the corrosion of the magnesium alloy, resulting in a lot of corrosion pits on the magnesium alloy surface under the corrosion product layer.

The evolution information of corrosion process is crucial to explore the mechanism of corrosion. Currently, most researches about corrosion of magnesium alloy used traditional testing techniques to obtain corrosion information, lacking the direct tracking and monitoring of the corrosion evolution process. Hence, this paper focuses on in situ corrosion study of AZ91 magnesium alloy. The technology with spatial resolution capability observed the changes in magnesium alloy surface at different times in the corrosion process in situ. Meanwhile, the in situ electrochemical technology was used to monitor the changes in micro-electrochemical signals during the corrosion process of magnesium alloy under different stresses.

The high specific strength makes magnesium alloys have a wide range of applications in aerospace, military, automotive, marine and construction industries. However, its poor corrosion resistance and weldability have limited its development and application. Friction stir welding (FSW) can effectively avoid the defects of fusion welding. However, the microstructure, mechanical properties and corrosion behavior of FSW joints in magnesium alloys vary among different regions. The purpose of this paper is to review the corrosion of magnesium alloy FSW joints, and to summarize the protection technology of welded joints.

The corrosion of magnesium alloy FSW joints includes electrochemical corrosion and stress corrosion. This paper summarizes corrosion protection techniques for magnesium alloys FSW joints, focusing on composition, microstructure changes and surface treatment methods.

Currently, this research is mainly focused on enhancing the corrosion resistance of magnesium alloy FSW joints by changing compositions, structural modifications and surface coating technologies. Refinement of the grains can be achieved by adjusting welding process parameters, which in turn minimizes the effects of the second phase on the alloy’s corrosion resistance.

This paper presents a comprehensive review on the corrosion and protection of magnesium alloys FSW joints, covering the latest research advancements and practical applications. It aims to equip researchers with a better insight into the field and inspire new studies on this topic.

The purpose of this paper is to research the corrosion behavior of AM60B magnesium alloy in simulated acid rain. Specifically, this paper aims to investigate the effect of pH on the corrosion behavior of the alloy.

Electrochemical methods and surface analysis were applied to study the corrosion behavior of AM60B magnesium alloy in simulated acid rain.

Results showed that changes in pH can influence the corrosion potential and corrosion current of the alloy. In particular, the anodic process was affected. The protective film on the surface of AM60B magnesium alloy was destroyed in simulated acid rain. The type of corrosion attack observed on the surface of the alloy was pitting damage. Numerous deep pits were formed on the surface. Corrosion products were mainly composed of MgO and MgAl₂(SO₄)₄ · 2H₂O.

The paper provides fundamental experimental data for clarifying the mechanism of the effects of acid rain on the corrosion of magnesium alloys.

The purpose of this paper is to reveal the solute segregation behavior in the molten and solidified regions during direct chill (DC) casting of a large-size magnesium alloy slab under no magnetic field (NMF), harmonic magnetic field (HMF), pulsed magnetic field (PMF) and two types of out-of-phase pulsed magnetic field (OPMF).

A 3-D multiphysical coupling mathematical model is used to evaluate the corresponding physical fields. The coupling issue is addressed using the method of separating step and result inheritance.

The results suggest that the solute deficiency tends to occur in the central part, while the solute-enriched area appears near the fillet in the molten and solidified regions. Applying magnetic field could greatly homogenize the solute field in the two-phase region. The variance of relative segregation level in the solidified cross-section under NMF is 38.1%, while it is 21.9%, 18.6%, 16.4% and 12.4% under OPMF2 (the current phase in the upper coil is ahead of the lower coil), HMF, PMF and OPMF1 (the current phase in the upper coil lags behind the lower coil), respectively, indicating that OPMF1 is more effective to reduce the macrosegregation level.

There are few reports on the solute segregation degree in rectangle slab under magnetic field, especially for magnesium alloy slab. This paper can act a reference to make clear the solute transport behavior and help reduce the macrosegregation level during DC casting.

This paper aims to investigate the effect of Cu content and T6 heat treatment on the mechanical properties and the tribological performance of SiCp/Al-Si-Cu-Ni-Mg hybrid composites at an elevated temperature.

The stir casting method was used to synthesize SiCp/Al-12Si-xCu-1Ni-1Mg (x = 2, 3, 3.5, 4, 4.5, 5 Wt.%) composites containing 20 vol% SiC. The hardness and tensile strength of the aluminum matrix composites (AMCs) at room temperature and elevated temperature were studied, and the wear mechanism was investigated using scanning electron microscopic and energy dispersive spectroscopy.

Results indicate that the hardness and tensile strength of the AMCs are affected significantly by T6 heat treatment and Cu content. The high-temperature friction and wear mechanism of AMCs is the composite wear mechanism of oxidation wear, adhesion wear, abrasive wear, peeling wear, high-temperature softening and partial melting. Among them, adhesion wear, high-temperature matrix softening and local melting are the main wear mechanisms.

The influence mechanism of Cu content on the hardness, tensile strength and high temperature resistance of AMCs was explained by microstructure. And the results further help to explore the application of AMCs in high temperature.