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To improve the electrochemical corrosion resistance of cold sprayed Al coating.

A cold sprayed aluminum (Al) coating fabricated on S355 structural steel was oxidized using a micro arc oxidation (MAO). The electrochemical corrosion and impedance spectroscopy were tested to investigate its corrosion performance.

The MAO film is primarily α-Al₂O₃ and γ-Al₂O₃, which increases its density and surface quality. The corrosion potential is positively shifted by 0.2 V, and the electrochemical impedance is significantly increased.

A cold sprayed Al coating on S355 steel was first oxidized using a MAO. The effects of MAO on the microstructure of Al coating were investigated to analyze its electrochemical corrosion behavior.

Aluminum alloy is considered an ideal material in aerospace, automobile and other fields because of its lightweight, high specific strength and easy processing. However, low hardness and strength of the surface of aluminum alloys are the main factors that limit their applications. The purpose of this study is to obtain a composite coating with high hardness and lubricating properties by applying GO–PVA over MAO coating.

A pulsed bipolar power supply was used as power supply to prepare the micro-arc oxidation (MAO) coating on 6061 aluminum sample. Then a graphene oxide-polyvinyl alcohol (GO–PVA) composite coating was prepared on MAO coating for subsequent experiments. Samples were characterized by Fourier infrared spectroscopy, X-ray diffraction, Raman spectroscopy and thermogravimetric analysis. The friction test is carried out by the relative movement of the copper ball and the aluminum disk on the friction tester.

Results showed that the friction coefficient of MAO samples was reduced by 80% after treated with GO–PVA composite film.

This research has made a certain contribution to the surface hardness and tribological issues involved in the lightweight design of aluminum alloys.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-12-2023-0427/

This chapter analyzes Mao Zedong’s decision-making code in foreign policy decisions made during his years as China’s leader: 1949–1976. I examine six decisions in China’s foreign policy during Mao’s tenure: China’s involvement in the Korea war (1951), Annexation of Tibet (1951), attacking the Taiwanese islands (1954), China’s war with India (1962), its involvement in the Vietnamese war (1964), and 1969 incident with the Soviet Army. This, in order to shed more light on the decision-making of leaders from the Far East, and to try and understand insights pertaining to the current foreign policy of China.

The analysis was conducted using the Applied Decision Analysis (ADA) method, based on historical materials, testimonies, and reports. The analysis demonstrates that Mao followed the poliheuristic decision rule in these decisions. Chairman Mao was making his decisions while choosing the most rational, cost-effective decision among alternatives that did not place his political status at risk.

The purpose of this paper is to explore the effect of ZnO on the structure and properties of micro-arc oxidation (MAO) coating on rare earth magnesium alloy under large concentration gradient.

The macroscopic and microscopic morphology, thickness, surface roughness, chemical composition and structure of the coating were characterized by different characterization methods. The corrosion resistance of the film was studied by electrochemical and scanning Kelvin probe force microscopy. The results show that the addition of ZnO can significantly improve the compactness and corrosion resistance of the MAO coating, but the high concentration of ZnO will cause microcracks, which will reduce the corrosion resistance to a certain extent.

When the concentration of zinc oxide is 8 g/L, the compactness and corrosion resistance of the coating are the best, and the thickness of the coating is positively correlated with the concentration of ZnO.

Too high concentration of ZnO reduces the performance of MAO coating.

The MAO coating prepared by adding ZnO has good corrosion resistance. Combined with organic coatings, it can be applied in corrosive marine environments, such as ship parts and hulls. To a certain extent, it can reduce the economic loss caused by corrosion.

The effect of ZnO on the corrosion resistance of MAO coating in electrolyte solution was studied systematically, and the conclusion was new to the common knowledge.

This study aims to investigate whether and how auditors responded to the documented increases in earnings management after split-share structure reform (SSSR) in China, as manifested in auditors’ propensity to issue modified audit opinions (MAOs) after the SSSR. This study further investigates how client importance and auditor size influence auditors’ response to earnings management after the SSSR.

This study adopts logit regression models to investigate auditors’ propensity to issue MAOs to their clients that appear to manage earnings after the SSSR. Initially, including all Chinese publicly listed firms from the CSMAR database, the sample for final analyses consists of 21,904 firm-year observations for 1,290 unique listed firms during the period 2001–2020. The sample period surrounds the implementation of the SSSR, which started in 2005, allowing the examination of auditors’ propensity to issue MAOs after vis-à-vis before the SSSR.

The authors find that non-Big10 auditors in China were less likely to issue MAOs to their economically important clients who appear to manage earnings after SSSR. However, in the years of non-tradeable shares being released to the markets, both Big10 and non-Big10 auditors were less likely to issue MAOs to their economically important clients who appear to manage earnings. The findings suggest that auditors may have compromised auditor independence in response to earnings management after the SSSR, likely due to the pressure from their economically important clients.

This paper contributes to the literature, specifically the practice and theory in auditing, by shedding light on ever-changing auditors’ reporting behaviour, especially with regard to auditor independence. It also adds to the growing body of literature on the impact of institutional changes on auditing practices worldwide. The findings of this study further suggest that the recently documented declining demand for high-quality audits after the SSSR may be motivated by the clients’ intention to manage earnings after the SSSR.

The purpose of this paper is to improve the corrosion resistance of the 6061-Al alloy as the battery pack material for electric vehicles, and the nano-SiC/MAO composite coating was prepared.

The corrosion resistance of coatings was evaluated by the global electrochemical test, and the local electrochemical impedance spectroscopy (LEIS) was used to study the local corrosion mechanism. The laser confocal microscope, scanning electron microscope and X-ray diffractometer (XRD) were used to characterise coatings.

Results showed that the impedance of nano-SiC/MAO coating was 1–2 times higher than MAO coating, and the main corrosion product was Al(OH)₃. LEIS results showed that the impedance of the nano-SiC/MAO coating was two times higher than the MAO coating. The defective SiC/Micro-arc oxidation coating still had high corrosion resistance compared to the MAO coating.

The physical model of the local corrosion mechanism for SiC/MAO composite coating in “cavity-fracture collapse” mode was proposed.

This paper aims to investigate the effects of deposition time on the structure and anti-corrosion properties of a micro-arc oxidation (MAO)/Al coating on AZ31B Mg alloy.

The study describes the fabrication of the coating via a combined process of MAO with multi-arc ion plating. The structure, composition and corrosion resistance of the coatings were evaluated using scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction and electrochemical methods.

The Al-layer is tightly deposited with a good mechanical interlock along the rough interface due to the Al diffusion. However, the Al layer reduces the anti-corrosion of MAO-coated Mg alloy because of structural defects such as droplets and cavities, which act as channels for corrosive media infiltration towards the substrate. Fortunately, the Al layer improves the substrate corrosion resistance owing to its passive behaviour, and the corrosion resistance can be enhanced with increasing deposition time. All results indicate that a buffer layer fabricated through the duplex process improves the interfacial compatibility between the hard coating and soft Mg alloys.

An MAO/Al duplex coating was fabricated via a combined process of MAO and physical vapour deposition. MAO/Al duplex coatings exhibit obviously passive behaviours on AZ31 Mg alloy. The structure and corrosion resistance of MAO/Al coatings were investigated.

The purpose of this paper is to investigate the effect of high-intensity pulsed ion beam (HIPIB) intensity on the structure and corrosive properties of microarc oxidation (MAO) films on AZ31 magnesium alloy and explore the mechanism for modified anti-corrosion properties of irradiated films.

The energy deposited on the coating surface influences the remelting process of the MAO coatings significantly, which was closely related to the intensity of HIPIB; therefore, HIPIB with various intensities of 100-350 A/cm², was selected to modify the MAO films on AZ31 magnesium alloy. The changes in film structure and phase structure of modified films were characterized by scanning electron microscopy and X-ray diffractometry (XRD) with CuKα, respectively. The corrosive behavior of the MAO films was featured with polarization curves and electrochemical impedance spectrum in 3.5 per cent NaCl solution on a PAR 2273 electrochemical workstation.

The results clearly show that a dense, continual and remelted layer with a few micrometers in thickness was obtained on the irradiated surface at 200 A/cm², which are mainly responsible for the modified and optimal anti-corrosion property of MAO films by suppressing/retarding the process of the corrosive electrolyte infiltration into magnesium substrate surface.

The paper reveals that HIPIB irradiation could modify the corrosion resistance by producing a remelted compact layer on the MAO film surface at a suitable irradiation parameter and explored the modified mechanism of MAO films.

Aluminum alloy is susceptible to chloride ion attack in sea water, resulting in pitting damage and hence serious security risks for the related applications. To improve the corrosion resistance of Al alloy, micro-arc oxidation (MAO) technology has been developed to produce a protective dense oxide layer on top of Al alloy. However, the mechanism of MAO-induced corrosion resistance is still not fully understood, particularly on local corrosion issue. This paper aims to focus on comprehensively studying the corrosion-resistance mechanism by a series of technologies.

The corrosion behavior of samples was studied by open circuit potential (OCP), potentiodynamic polarization (PDP), electrode impedance spectroscopy (EIS) and localized electrode impedance spectroscopy (LEIS) tests in NaCl solution.

The MAO-coated Al alloy shows a more positive corrosion potential and a higher corrosion current density compared to the untreated counterpart, indicating a significantly enhanced corrosion-resistance. The study of surface morphology and structure also suggest significantly enhanced corrosion-resistance due to the MAO treatment.

Based on the results, a new corrosion model was proposed to describe the influence of MAO treatment on the corrosion process and corrosion mechanism of Al alloy, providing insights on the design of the corrosion-resistance coating for metallic alloys in marine applications.

The purpose of this paper is to investigate the effect of Na₂SiO₃ concentration on the microstructure and corrosive properties of microarc oxidation (MAO) coating on Al-Mg-Sc alloy and explore microstructure evolution rule of Al substrate in the contact area.

The Na₂SiO₃ concentration in electrolytes influenced the microstructure and corrosion behavior of MAO coatings. Instantaneous high temperature and high pressure due to microarc discharge caused annealing treatment. The corrosive behavior of the MAO coating was featured with polarization curves and electrochemical impedance spectrum in 3.5 Wt.% NaCl solution.

The substrate in the contact area existed the instantaneous annealing treatment, which caused obvious recrystallization. The coating prepared in electrolyte containing 7 g/L Na₂SiO₃ exhibited the highest protective properties in 3.5 Wt.% NaCl solution.

MAO treatment could increase the corrosion resistance by producing a protective layer on the Al-Mg-Sc alloy surface at a suitable Na₂SiO₃ concentration and microstructure evolution rule of Al substrate in the contact area was obtained.