Bare Aluminum Alloy Research Articles

Corrosion Properties of the Composite Coatings Formed on PEO Pretreated AlMg3 Aluminum Alloy by Dip-Coating in Polyvinylidene Fluoride-Polytetrafluoroethylene Suspension.

This paper presents the results of an evaluation of corrosion properties of PEO pretreated AlMg3 aluminum alloy samples with polymer coatings obtained by dip-coating in a suspension of superdispersed polytetrafluoroethylene (SPTFE) in a solution of polyvinylidene fluoride (PVDF) in N-methyl-2-pyrrolidone at different PVDF:SPTFE ratios (1:1, 1:3, 1:5, and 1:10). The electrochemical tests showed that samples with a coating formed at a ratio of PVDF to SPTFE of 1:5 possessed the best corrosion properties. The corrosion current density of these samples was more than five orders of magnitude lower than this parameter for bare aluminum alloy. During the 40-day salt spray test (SST) for samples prepared in a suspension at a PVDF:SPTFE ratio of 1:1-1:5, the formation of any pittings or defects was not detected. The PVDF:SPTFE 1:5 sample demonstrated, as a result of the 40-day SST, an increase in corrosion current density of less than an order of magnitude. The evolution of the protective properties of the studied samples was assessed by a two-year field atmospheric corrosion test on the coast of the Sea of Japan. It was revealed that the samples with the PVDF:SPTFE 1:5 coating had electrochemical parameters that remained consistently high throughout the one year of exposure. After this period, the polymer layer was destroyed, which led to a deterioration in the protective characteristics of the coatings.

A facile preparation of durable superhydrophobic PFA coatings with superior anti-icing, anti-corrosion and self-cleaning performance

The potential of superhydrophobic coatings for various applications has been widely recognized. However, preparing durable superhydrophobic coatings on metal surfaces remains a significant challenge. Perfluoroalkoxy Alkane (PFA), a fluorine-rich material, has recently emerged as a promising candidate for constructing superhydrophobic coatings. In this study, a mechanically stable superhydrophobic PFA coating was prepared using a simple combination of electrodeposition and annealing. The prepared PFA coating displays excellent water repellency, as evidenced by a water contact angle of 171 ± 0.3° and a sliding angle of 1.0 ± 0.4° The water contact angle of the coating only decreases by 0.6°after undergoing 400 tape stripping tests, indicating the remarkable stability. The PFA coating significantly prolongs the freezing time of water droplets on a cool surface at temperatures of -6 °C, -8 °C, and -10 °C, with improvements of 19.4, 72.5, and 47.8 times respectively. The corrosion current density on the coated surface is reduced by four orders of magnitude compared to bare aluminum alloy, and the PFA coating exhibits a high inhibition corrosion efficiency of 99.995 %. Furthermore, the coating possesses exceptional self-cleaning performance by repelling dirt particles and maintaining a clean surface. Consequently, the developed superhydrophobic PFA coating holds significant promise for long-lasting anti-icing, anti-corrosion and self-cleaning applications.

Chelating agent stimulated LDH post-treatment of PEO coated AA2024

Layered double hydroxides (LDHs) are well known and broadly investigated on bare aluminum alloys, but not on PEO treated aluminum where source of aluminum ions is restricted. The additions of the chelating agents were tested in this work to stimulate the LDH formation on PEO (plasma electrolytic oxidation) coated aluminum alloy AA2024. 1,3-diamino-2-hydroxipropane-N,N,N’,N’-tetraacetic acid (DHPTA) was identified as the most effective one among tested additives. Its performance in terms of LDH growth stimulation was investigated. The DHPTA additive provides an increase of the pH of the LDH synthesis compared to previously known methods to achieve hydration of aluminum oxide from PEO as the initial stage of PEO etching, as well as the formation of soluble complex compounds of Zn-DHPTA, necessary for the formation of ZnAl LDH. The process of LDH formation was also followed by intercalation of DHPTA ions into LDH galleries. It was shown that LDH was formed both on the surface and insight the pores of parental PEO coating. Moreover, it imparted lubricating properties to the hybrid coating. Finally, PEO-LDH coating demonstrated higher corrosion resistance and long-term stability comparing to the PEO coated aluminum alloy.

Bilayer coating fabricated on aluminum alloy substrates with superamphiphobicity, corrosion resistance, self-cleaning, and delayed icing properties

To address the functional failure caused by low-surface-tension liquid wetting and adhesion in superhydrophobic materials, in this study, we constructed a bilayer coating with superamphiphobic properties using an epoxy (Ep) bonding layer and an organosilane-grafted attapulgite (OG-ATP) layer through spray-coating technique. The prepared superamphiphobic bilayer coating exhibited high contact angles (CAs) and low sliding angles (SAs) for cold water (25 °C), hot water (85 °C), glycerol, ethylene glycol, peanut oil, and even n-hexadecane (CA = 150.4 ± 0.3° and SA = 7 ± 2°) with surface tension of 27.5 mN m−1. Surface morphology and elemental analysis confirmed the coating's unique micro-nano hierarchical structure and low surface energy characteristics. Electrochemical impedance spectroscopy (EIS) results showed that the surface charge transfer resistance (Rct) and low-frequency modulus (|Z|0.01Hz) were enhanced by 6–7 orders of magnitude compared to the bare aluminum alloy substrate. The anti-corrosion performance remained stable even after 5 days of 3.5 wt% NaCl immersion. Additionally, icing experiments with water droplets at −10 °C and −15 °C revealed a significant delay in ice formation on the substrate protected by the bilayer coating. The development of this protective material, combining superamphiphobicity, self-cleaning, corrosion resistance, and anti-icing functions, will provide advanced technological reserves in areas such as marine, aviation, transportation, and manufacturing.

Corrosion Modeling of Aluminum Alloys: A Brief Review

AbstractCorrosion remains a critical concern in various industries, particularly in applications involving aluminum alloys due to their widespread usage as light structural materials. This work provides a comprehensive overview of the recent advances in modeling techniques for better understanding the corrosion behavior of aluminum alloys. The present study encompasses the state‐of‐the‐art of computational approaches, highlighting their strengths and limitations. Special attention is given to transport models, galvanic couples, localized corrosion, and the incorporation of different factors, such as pH variations, electrolyte thicknesses and dynamic electrolytes into corrosion models. Furthermore, the review delves into both bulk and atmospheric corrosion models. On the other hand, this work also emphasizes a clear differentiation between models designed for bare aluminum alloys and those tailored for coated ones. Additionally, it addresses certain challenges associated with the experimental validation of such models. This review concludes with perspectives on both sophisticated transport models to bridge the gap between industrial and academic investigations, as well as the integration of machine learning and artificial intelligence techniques in corrosion modeling, offering promising directions for future research in this field.

Buckling characteristics of carbon fiber composite/aluminium alloy combined cylindrical shells under external hydrostatic pressure

The buckling behaviour of combined shells fabricated from aluminium alloy and carbon fiber–reinforced polymer (CFRP) composites subjected to external hydrostatic pressure were investigated. Three sets of combined cylindrical shells with different combinations and one set of bare aluminium alloy cylindrical shells were designed and fabricated. The wall thickness of each cylindrical shell was measured. All the cylindrical shells were tested under external hydrostatic pressure, and the buckling load and final collapsed mode were recorded. Numerical models with real imperfections were established, linear and nonlinear analyses were performed to evaluate the buckling loads of cylindrical shells. The experimental and numerical results agreed favourably. On this basis, the effects of the thickness-diameter ratio, combination method and geometric imperfection on the buckling of combined cylinders were studied. This research can provide a reference for the design of combined shells made from CFRP and metal shell.

Ultrasound-assisted cast-on method: Obtaining high-quality metallurgical bonds between a bare steel insert and A354 aluminum alloy within a composite casting

A bare steel insert is difficult to be bonded to an aluminum alloy using a cast-on method for manufacturing bimetal composite castings. This article describes an ultrasound-assisted cast-on (UACO) approach in obtaining high quality metallurgical bonds between bare steel inserts and A354 aluminum alloy. Hot dip tests were carried out to determine the reaction times required to obtain high quality metallurgical bonds with and without high-intensity ultrasonic vibrations. Ultrasonic vibrations were then applied through the bare steel insert to assist the cast-on method for making bimetal castings. Microstructural characterization revealed that oxide and porosity defects that covered the interface of the steel/melt in a bimetal casting made by conventional cast-on methods were totally removed in castings subjected to high-intensity ultrasonic vibrations. Push-out tests confirmed that the mean shear strength in such composite castings increased with increasing intensity of ultrasonic vibrations, from about 3.1 MPa at 0 µm amplitude to about 91.6 MPa at about 80 µm amplitude of ultrasonic vibrations. The mean shear strength associated with the UACO process was about 85 % and 39 % higher than that of the Al-Fin process and Cummins process, respectively. Theoretical analyses were performed to understand experimental results. It is believed that ultrasound induced phenomena that occur at or near the steel/melt interface play an important role in forming high quality metallurgical bonds between bare steel inserts and aluminum castings. Research results suggest that the UACO process can be a cost-effective replacement for various cast-on processes for manufacturing bimetal composite castings of high internal integrity.

Investigating the effect of curing temperature on the corrosion resistance of epoxy-based composite coatings for aluminium alloy 7075 in artificial seawater.

Araldite LY5052 epoxy resin and Aradur HY5052 hardener were used in a ratio of 100 : 38 to produce composite coatings containing 0.05 proportion of functionalized SiO2. Coating samples were cured at curing temperatures of 60, 80, 100, 120, and 140 °C. The results of Fourier Transform Infrared Spectroscopy (FTIR) verified that silica particles were successfully functionalized with methyltrimethoxysilane (MTMS)/3-aminopropyl-triethoxysilane (APTES). The epoxide and Si-O bond peaks in the EHS100 coating were present due to the effective incorporation of functionalized silica (FSiO2) particles in the polymeric matrix (epoxy resin). The surface morphology of the bare aluminium alloy AA7075 and EHS100 coating was investigated by Field Emission Scanning Electron Microscopy (FE-SEM). Additionally, corrosion analysis was conducted at room temperature using an electrolytic solution of artificial seawater, prepared according to ASTM standard D1141-98. Charge transfer resistance (Rct) was shown to increase by 86.43, 92.15, 94.76, 90.65, and 83.96% for EHS60, EHS80, EHS100, EHS120, and EHS140 in comparison to bare AA7075 substrate using electrochemical impedance spectroscopy (EIS) examination. Furthermore, potentiodynamic polarization (PDP) measurements were carried out to determine the corrosion rates, which demonstrated a drop of 55.98, 98.96, 99.37, 98.33, and 50.39% for EHS60, EHS80, EHS100, EHS120, and EHS140, as compared to the bare AA7075 sample. The highest charge transfer resistance (29.77 kΩ) and lowest corrosion rate (0.00078 mm per year) were recorded for EHS100, which reveals that the EHS100 coating has the best anti-corrosion performance and provides the maximum corrosion protection for the aluminium alloy AA7075 substrate.

Comparative Mechanical Study of Pressure Sensitive Adhesives over Aluminium Substrates for Industrial Applications.

The use of adhesives for fixing low-weight elements is showing increasing interest in the industry, as it would reduce the weight of the assembly, costs, and production time. Specifically, the application of pressure-sensitive adhesives (PSAs) to join non-structural naval components to aluminium substrates has not yet been reported. In the present work, a study of the mechanical behaviour of different double-sided PSAs applied on bare aluminium alloy substrates is performed. The influence of surface roughness, surface chemical treatments, and the matrix of the adhesives is studied through different mechanical tests, such as shear, T-peel, and creep. The application of an adhesion promoter improved the mechanical behaviour. Low roughness substrates provided better performance than ground samples. Acrylic foam adhesives were subjected to creep tests, whose results were fitted to a simple mathematical model, predicting the fracture time as a function of the applied load.

In situ fabrication of flower-like ZnO on aluminum alloy surface with superhydrophobicity

A hierarchical structure ZnO is fabricated on aluminum alloy substrate by hydrothermal method at low temperature of 90 °C, following treated by the solution of PDMS to achieve superhydrophobicity. We investigate the effect of PDMS concentrations on surface hydrophobicity. Results are shown that the optimum superhydrophobic surface (Al-ZnO-PDMS8) possesses a water contact angle as high as 161.1° and a low water sliding angle of 3.3°. The chemical compositions and surface morphologies are investigated using FTIR, XPS, EDS, FESEM, and AFM. The delayed-icing time of 7 μL water droplets on Al-ZnO-PDMS8 at − 15 °C is 5.46 times longer than that of the bare aluminum alloy surfaces. Furthermore, the influence of temperature and droplet volume on delayed-icing time is measured and analyzed. Also, the superhydrophobic surface displays excellent anti-frost performance with decreased icing weight and area. Meanwhile, the superhydrophobic surface shows good self-cleaning performance by different types of daily water-based pollutions. The behavior of impacting water droplet is researched by using highspeed photography, indicating that pollutants were difficult to adhere to the surfaces, which could be easily cleaned up by rolling water droplets. These investigations are believed that there is an extent promotion to practical applications of superhydrophobic surface, especially in the fields of anti-icing and self-cleaning.

Concrete-filled and bare 6082-T6 aluminium alloy tubes under in-plane bending: Experiments, finite element analysis and design recommendations

The application of aluminium alloys in structural engineering is growing owing to their high strength-to-weight ratio, aesthetic appearance and excellent resistance to corrosion. However, the low modulus of elasticity of aluminium poses adverse effects on the flexural response of structural members made of aluminium alloys. In case of tubular members, the performance can be improved with the addition of concrete infill. Research on the flexural response of concrete-filled aluminium alloy tubes is still minimal. This study presents experimental and numerical investigations on the behaviour of concrete-filled and bare 6082-T6 aluminium alloy tubular members under in-plane bending. In total 20 beams, including 10 concrete-filled aluminium alloy tubular (CFAT) and 10 bare aluminium alloy tubular (BAT) specimens, were tested. The specimens comprised of square and rectangular hollow sections and were filled with 25 MPa nominal cylinder compressive strength concrete. The experimental results are reported in terms of failure mode, flexural strength, flexural stiffness, ductility and bending moment versus mid-span deflection curve. Compared to the BAT specimens, the counterpart CFAT specimens have shown remarkably improved flexural strength, stiffness and ductility due to the concrete infill and the improvement is more pronounced for the specimens with thinner sections. Finite element models of BAT and CFAT beams were developed by taking into account the nonlinearities in geometry and material and validated against the experimental data. A parametric study considering a broad range of cross-sections and different concrete grades was conducted based on the validated models. The FE results have shown that the flexural strength of the BAT and CFAT members increases with the increase of cross-sectional aspect ratio, wall thickness and concrete grade. The results obtained from experiments and numerical analysis for BAT members were used to assess the flexural capacity predictions and the applicability of the slenderness limits provided in the European standards. It was demonstrated that the slenderness limits provided by Eurocode 9 are conservative for Class A aluminium sections. Hence, revised Class 1, Class 2 and Class 3 limits are proposed which appear to be better applicable to Class A aluminium alloys. In the absence of design specifications for CFAT flexural members, the design rules for concrete-filled steel tubular flexural members provided by Eurocode 4 were adopted and the material properties of steel were replaced with those of aluminium alloy. It was shown that the proposed design methodology is suitable for the design of CFAT flexural members. Moreover, a slenderness limit for compact sections of CFAT flexural members is proposed based on Eurocode 4 framework.

A pH-responsive cerium-imidazole decorated ZIF-8 to achieve self-healing barrier property for epoxy coating on Al alloy by controlled release

Ce-based imidazole complex (Ce-IM/ZIF-8) nanoparticles (NPs) were fabricated by doping cerium ions (Ce3+ /Ce4+) in zeolite imidazolate framework-8 (ZIF-8) through a one-pot co-precipitation method. The stimuli-responsive release of Ce3+/Ce4+ species from the Ce-IM/ZIF-8 NPs under acidic conditions was confirmed by UV–Vis spectroscopy. Electrochemical impedance spectroscopy and scanning electron microscope were applied to evaluate the corrosion inhibition efficiency of Ce-IM/ZIF-8 NPs on bare aluminum alloy, and it demonstrates that the released Ce3+/Ce4+, Zn2+ ions and imidazole could absorb on the surface of Al alloy by chelating effect, forming a compact corrosion barrier on the Al substrate. Furthermore, the Ce-IM/ZIF-8 NPs were encapsulated into epoxy (EP) resin to obtain a composite coating, and it is found that when the NPs addition amount was 1 wt%, the EP-based composite coating exhibits excellent corrosion barrier and promising self-healing ability, with its impedance at 0.01 Hz maintaining 2.2 × 108 Ω·cm2 even after 6 cycles of aging tests (720 h), which could be ascribed to the synergistic inhibition of released Ce ions and imidazole molecules on Al substrate beneath the defective coating.

Laser textured dimple-patterns to govern the surface wettability of superhydrophobic aluminum plates

A laser texturing technique herein can endow bare aluminum alloy surface with regular dimple-pattern array and thus generates a case hardening. After STA treatment, these laser-textured samples become superhydrophobic. The surface wettability of the laser-textured samples can be regulated by controlling the dimple-pattern dimensions during the laser processing. It is noteworthy that a fluorescence method is utilized to record the zones on the superhydrophobic surface penetrated by small enough water molecules. Compared with a general method of the Cassie-Baxter theoretical calculation, this fluorescence method intuitively exhibits the air trapping ability of the superhydrophobic surface. Furthermore, the laser-textured superhydrophobic samples have a notable hysteresis phenomenon at the initial period of UMT friction because the air cushion trapped within superhydrophobic samples have strong repellency against water droplets on the hydrophilic steel ball. Additionally, such samples display strong mechanical stability in comparison with bare aluminum alloy because of the presence of case hardening on the surface of the laser patterns. The research results above provide a valuable reference for designing a surface with different wettability, which may inspire practical applications in the fields of fluid transport, droplet manipulation, water harvesting and microfluidic devices.

Organic carbon dot coating for superhydrophobic aluminum alloy surfaces.

A novel fluorine-free and silicon-free superhydrophobic aluminum alloy (treated-Al) is fabricated by chemical etching using hydrochloric acid and hydrogen peroxide and modified with an organic carbon dot (OCD) coating. The water contact angle (CA) of the treated-Al surface increases with the OCD concentration. When etched aluminum (etched-Al) is modified with 0.5 mg/ml OCDs, a CA of 161.4° is achieved, which indicates good nonwettability. SEM results verify that porous microstructures with cavities are uniformly distributed on the surface of etched-Al, in contrast to the bare aluminum alloy, which forms a primary rough structure. After treatment with 0.5 mg/ml OCDs, a nanoparticle coating is dispersed on the rough structures of treated-Al-0.5, which can trap air and make a water droplet essentially rest on a layer of air. The treated-Al-0.5 material has good self-cleaning properties and can sweep away contaminants at both 20 and 0°C. The Ecorr and Icorr of treated-Al-0.5 are − 0.56 V and 2.82 × 10−6 A/cm2, respectively, which shows good anticorrosion performance.

Simultaneous mapping of nanoscale topography and surface potential for the study of localized corrosion in 2024-T3 aluminum alloy and corrosion resistance introduced by a superhydrophobic coating

The localized corrosion phenomenon on 2024-T3 aluminum alloy is studied at nanoscale using simultaneous mapping of topography and surface potential by atomic force microscope in this work. The corrosion resistance imparted by a superhydrophobic coating is also studied using the same procedure for comparison. The results from simultaneous mappings revealed that the surface potential images obtained from SKPM images are capable of predicting the probable sites for the initiation of localized corrosion in the case of bare aluminum alloy substrate. The corrosion parameters for both substrates were quantified by potentiodynamic polarization.

The investigation of corrosion behavior of ZrO2–Al2O3-inhibitor/AA2024 nanocomposite thin film using sol-gel and AHP-TOPSIS method

Nowadays, the sol-gel thin films doped with corrosion inhibitor have suggested enhancing corrosion resistance of materials. In the present work, ZrO2 and ZrO2–Al2O3 thin films with benzotriazole (BTA) and cerium nitrate inhibitors were applied on the aluminum alloy substrate by using dip-coating process, and heat treated at 150 °C for 2 h with heating rate of 1 °C/min. Then, the crystalline phase, chemical composition, the microstructure and topography of thin films were evaluated by grazing incidence x-ray diffraction, energy dispersive spectroscopy, field emission scanning electron microscopy, and atomic force microscopy, and the average thickness of thin films was measured by ellipsometry technique. In addition, electrochemical impedance spectroscopy, and potentiodynamic polarization investigations were used to study the corrosion protection properties of thin films. Eventually, the experimental results related to the three independent coating conditions (sample A, B, D) were investigated by analytic hierarchy process (AHP) and technique for order preference by similarity to ideal solution (TOPSIS). Results indicate the formation of composite thin films without microcracks comparison to the single-component coating, and electrochemical impedance tests after 4 day immersion in the corrosive environment illustrates an improvement of corrosion resistance of sample C (with the first and outside layer of ZrO2 and two middle layers of ZrO2, Al2O3 and BTA) more than 5 times compare to the bare AA2024 aluminum alloy. Additionally a decrease in the corrosion current density from 3.1 μA/cm2 for the uncoated aluminum to 0.2 μA/cm2, which was observed for sample C. Moreover, the data evaluation was studied by AHP and TOPSIS methods, which was presented the best thin films conditions for the sample B (Four layers of ZrO2 – Al2O3- BTA thin films on the AA2024 alloy) which was in good agreement with the experimental results.

Characterization of anodized and bare 7075-T6 aluminum alloy treated with Zr-based conversion coating

Characterization of anodized and bare 7075-T6 aluminum alloy treated with Zr-based conversion coating

Surface Modification of Aluminum 6061-O Alloy by Plasma Electrolytic Oxidation to Improve Corrosion Resistance Properties

In the present investigation, the plasma electrolytic oxidation (PEO) process was employed to form aluminum oxide coating layers to enhance corrosion resistance properties of high-strength aluminum alloys. The formed protective coating layers were examined by means of scanning electron microscopy (SEM) and characterized by several electrochemical techniques, including open circuit potential (OCP), linear potentiodynamic polarization (LP) and electrochemical impedance spectroscopy (EIS). The results were reported in comparison with the bare 6061-O aluminum alloy to determine the corrosion performance of the coated 6061-O alloy. The PEO-treated aluminum alloy showed substantially higher corrosion resistance in comparison with the untreated substrate material. A relationship was found between the coating formation stage, process parameters and the thickness of the oxide-formed layers, which has a measurable influence on enhancing corrosion resistance properties. This study demonstrates promising results of utilizing PEO process to enhance corrosion resistance properties of high-strength aluminum alloys and could be recommended as a method used in industrial applications.

Liquid-phase plasma assisted electrophoresis and sintering SiC/hBN nanocomposite ceramic coating on aluminum alloy for radiative heat dissipation

To improve the passive radiative heat dissipation property of aluminum alloy, a novel-structural SiC/hBN nanocomposite ceramic coating with high emissivity value (>0.86) was fabricated by one-pot liquid-phase plasma assisted electrophoresis and sintering (LPES) method. The special formation conditions of nanocomposite coating were optimized as: applied voltage was not lower than 600 V, temperature of electrolyte was ranged from 70 to 90 °C and the concentrations of SiC and hBN nanoparticles were 8 g/L and 40 g/L, respectively. The unique parameters contributed to the plasma assisted SiC and hBN nanoparticles synergistic electrophoresis and then sintering together by SiO2 based glassy phase. The infrared emissivity in the wavelength of 3–20 μm was enhanced by SiC/hBN nanocomposite coating, especially the value was up to 0.86 in 3–8 μm wavelength. The nanocomposite coating enabled the temperature drop by 10.4 °C for 1 W LED compared with the bare aluminum alloy, which leds to the cooling efficiency of 19.8%, respectively.The SiC/hBN ceramic nanocomposite coating fabricated by one-pot LPES process shows a novel strategy to design excellent radiative heat dissipation property coatings.

Optimization of surface texture fabricated by three-step microarc oxidation for self-lubricating composite coating of diesel engine piston skirts

A surface texture produced by three-step microarc oxidation (MAO) was optimized to improve the tribology performance of a self-lubricating composite coating for diesel engine piston skirts. WS2 was introduced into the self-lubricating composite coating as a self-lubricating additive. The effects of MAO’s varying electrical parameters in terms of stages and action time on the microstructure and chemical composition of the coatings were analyzed by XPS mapping, micron CT, SEM, XRD, and EDS mapping. Furthermore, friction-wear tests under dry lubricating were employed to evaluate the self-lubricating property of the composite coating. Compared to the bare ZL109 aluminum alloy, the optimized composite coating’s friction coefficients were reduced by 60%. Notably, the wear loss of cylinder liner samples matched with the optimized composite coating was almost zero under this work condition.