Anodized Aluminum Alloy Research Articles

Effects of the Process Conditions on the Color of Dye-Treated Anodized AA5052.

This study investigated the effects of process conditions (anodization time, coloring treatment time, dye concentration) on the color of dye-treated anodized aluminum alloy 5052 (AA5052). The color change of the anodic layers and amount of dye adsorbed were quantitatively analyzed using a UV-vis spectrophotometer. The color of the anodic layer turned darker as the anodizing time, coloring treatment time, and dye concentration increased due to the amount of dye adsorbed by the layers. As the anodizing time increased, the thickness of the anodic layers also increased, and a growth in the number of nanopore sites resulted in a greater amount of dye being adsorbed, causing the darkening of the color. Increase in the coloring treatment time and dye concentration led to a greater amount of dye being adsorbed in the anodic layers, thereby contributing to the darkening of the color. Quantitative analysis in the depth direction of the anodic layer using glow discharge optical emission spectroscopy revealed that the dye was mostly adsorbed on the outer region of the anodic layer.

Nickel fluoride as a surface activation agent for electroless nickel coating of anodized AA1050 aluminum alloy

In this study, the use of nickel fluoride tetrahydrate (NiF2·4H2O) as a surface activator and sealant at the same time for the coating of electroless nickel-phosphorus (Ni-P) on anodized aluminum alloy AA1050 is proposed. The usage of the activator resulted in more efficient deposition of Ni-P, improved adhesion properties, and increased wear and friction behavior as opposed to non-activated conditions. Scanning electron microscopy (SEM) and confocal laser microscopy (CLM) analyses of ultramicrotome-cut cross sections of Ni-P coated specimens, surface-activated by NiF2·4H2O, revealed a more well-structured metal-coating interface as opposed to non-activated conditions.

Study on Heat Transfer and Corrosion Resistance of Anodized Aluminum Alloy in Gallium-Based Liquid Metal

Gallium-based liquid metal (LM) inherits excellent thermophysical properties and pollution-free characteristics. However, it has long been a fatal problem that LM would cause serious corrosion and embrittlement on the classical substrate made of aluminum alloys in constructing chip cooling device. Here, anodic oxidation treatment was introduced on processing the aluminum alloy aiming to tackle the corrosion issues. The prepared anodic oxidation aluminum (AAO) coatings were composed of nanopore layers and barrier layers on a high-purity alumina matrix that were manufactured electrochemically. According to the measurement, the effective thermal conductivity of the anodized aluminum alloy increases with the total thickness of sample increasing. When the total thickness L exceeds 5 × 10−3 m, effects of the porous media on effective thermal conductivity are negligible via model simulation and calculation. It was experimentally found that aluminum alloy after surface anodization treatment presented excellent corrosion resistance and outstanding heat transfer performance even when exposed in eutectic gallium–indium (E-GaIn) LM over 200 °C. The convective heat transfer coefficient of LM for anodized sample reached the peak when the heat load is 33.3 W.

Hydrophobic surface treatments for improving the corrosion resistance of anodized AA2024-T3 alloys

The present study investigates the use of hydrophobic sealing treatments to improve the corrosion resistance of anodized aluminium alloys. Alternative hydrophobic processes to the hydrothermal sealing were tested. One is based on a monocarboxylic acid, myristic acid, and others involve the deposition of hybrid sol-gel film. The samples characterization was performed by Field Emission Scanning Microscopy. The hydrophobic properties were assessed by contact angle measurements, and Electrochemical Impedance Spectroscopy was used to study the anticorrosive properties. All the hydrophobic treatments improved the corrosion resistance of the anodized samples with respect to the hydrothermal treatment. The best results were obtained using the hybrid sol-gel film, where high impedance values are measured after long immersion periods in a 0.1 M NaCl solution. Especially good behaviour was observed in samples sealed with the sol-gel film when the sol was previously heated at 70 °C. This temperature was necessary to dissolve the aggregates that formed at room temperature, which contribute to a more efficient sealing.

PBT–anodized aluminum alloy direct joining: Characteristic injection speed dependence of injected polymer replicated into nanostructures

Roughened metal pieces and polymer can be joined via typical injection molding. We formed nanopores on the aluminum alloy surface by anodization and joined the alloy with polybutylene terephthalate. Tensile tests indicated the anodized metal and polymer joined with a shear strength of over 20 MPa. STEM-EDS analysis showed the polymer was replicated into the nanopores. We revealed the injection speed and joint strength have a negative correlation, which may result from the breaking of the nanopores. Additionally, measurement results for the polymer temperature indicated the local thermal decomposition could weaken the joint, especially in nanostructures. The joint strength dependence on the injection speed in anodic pores was similar to that of the NMT method. However, the characteristic correlation between the pack pressure and joint strength at high injection speeds has not been found for other surface treatments. These results provide insight into the behavior of injected polymers in nanostructures.

Electrochemical Behavior of Al-1.5Mg-0.05Sn-0.01Ga Alloy in KOH Ethanol-Water Solutions for Al-Air Battery

Self-corrosion of aluminum alloy anodes has always been the focus of research on aluminum-air batteries. In this paper, the performance of Al-1.5Mg-0.05Sn-0.01Ga anode in different 4M KOH ethanol-water mixed solutions were investigated. The experiment results show that the mixed solutions are distinctly inhibited anode self-corrosion and the anode utilization rate is improved effectively. The results of molecular dynamics simulation show that the ethanol would reduce the transport of K+ and OH− ions, decrease the conductivity of the mixed electrolyte. When the electrolyte contains more than 50% ethanol, the discharge performance of the battery will be rapidly deteriorated.

Studies on the sealing processes of corrosion resistant coatings formed on 2024 aluminium alloy with tartaric-sulfuric anodizing

Anodizing and post-treatment of aluminium alloys can effectively improve their surface corrosion resistance. In this work, we demonstrate the effectiveness a potassium permanganate sealing (M-S) treatment of tartaric‑sulfuric anodized 2024 aluminium alloy. This post anodic oxidation process was performed by immersing samples in the electrolyte solution at 70 °C for 30 min. Immersion and salt spray tests show such a M-S sealing processing can result in much improved corrosion resistance. The M-S treated samples can resist 240 h of salt spray test without corrosion pitting. Detailed morphological, microstructural and chemical analyses have been used to reveal mechanistic effects of the M-S retreatment. Interfacial electrochemical impedance measurements were performed to directly compare the corrosion behaviors of Al alloys after different post-treatments.

The Influence of PSA Pre-Anodization of AA2024 on PEO Coating Formation: Composition, Microstructure, Corrosion, and Wear Behaviors.

In the frame of the current work, it was shown that plasma electrolytic oxidation (PEO) treatment can be applied on top of phosphoric sulfuric acid (PSA) anodized aluminum alloy AA2024. Being hard and well-adherent to the substrate, PEO layers improve both corrosion and wear resistance of the material. To facilitate PEO formation and achieve a dense layer, the systematic analysis of PEO layer formation on the preliminary PSA anodized layer was performed in this work. The microstructure, morphology, and composition of formed PEO coatings were investigated using scanning electron microscopy (SEM), x-ray diffraction (XRD), and glow-discharge optical emission spectroscopy (GDOES). It was shown that under constant current treatment conditions, the PSA layer survived under the applied voltage of 350 V, whilst 400 V was an intermediate stage; and under 450 V, the PSA layer was fully converted after 5 min of the treatment. The comparison test with PEO formation on the bare material was performed. It was confirmed that during the “sparking” mode (400 V) of PEO formation, the PEO coatings, formed on PSA treated AA2024, were more wear resistant than the same PEO coatings on bare AA2024.

Experimental and theoretical investigation on calcium oxide and L-aspartic as an effective hybrid inhibitor for aluminum-air batteries

In this study, experimental method containing hydrogen evolution test, electrochemical measurement, galvanostatic discharge test and morphology analysis combining with theoretical method containing quantum chemical calculation and Monte Carlo simulation are used to study the inhibition performance of a new hybrid calcium oxide (CaO)/L-aspartic (Asp) inhibitor for AA5052 aluminum alloy anode of alkaline aluminum air batteries. The results show that the hybrid inhibitor has strong inhibitory effect on the self-corrosion and little impact on the discharge performance of AA5052 anode, so the discharge stability and efficiency, safety and storage time of aluminum air batteries are greatly improved. The optimal concentration is 10mM CaO and 4mM Asp. The hybrid inhibitor mainly retards anodic process of self-corrosion reaction, so it is more suitable in the case where discharge current density is not very large. According to the morphology simulation, the (11¯0) face of calcium hydroxide (Ca(OH)2) is suitable as the adsorption substrate, given that it provides more adsorption active sites. Combining experimental research with theoretical studies, the inhibition mechanism of the hybrid inhibitor is: calcium hydroxide formed from calcium oxide in alkaline electrolyte adheres to the surface of aluminum by geometric coverage effect, and promotes the adsorption of L-aspartic, which active sites are located on the oxygen atom of two hydroxyl groups and the nitrogen atom of amino group, thereby forming Ca(OH)2-Asp and Al-Asp monolayer composite films, they effectively block the dissolution of AA5052 alloy.

Effect of Mg content on discharge behavior of Al-0.05Ga-0.05Sn-0.05Pb-xMg alloy anode for aluminum-air battery

Al-0.05Ga-0.05Sn-0.05Pb-xMg alloys with different Mg content have been prepared. Electrochemical tests including constant current discharge test, current polarization test, electrochemical impedance spectroscopy (EIS) test, and Tafel test are performed. The surface states of the alloys after constant current discharge were analyzed by scanning electron microscopy (SEM) and energy disperse spectroscopy (EDS). X-ray diffraction (XRD) analysis was carried out. We find that different Mg contents have great influence on discharge performance of aluminum alloy anodes by changing the corrosion behavior. The SEM and XRD show that Mg can influence the distribution of corrosion and change the grain size to improve the discharge performance of aluminum anodes. Al-0.05Ga-0.05Sn-0.05Pb-0.1Mg shows the best electrochemical performance due to uniform corrosion and proper grain size. At 800 mA cm−2 constant current discharge, the potential of the aluminum anode can reach − 1.54 V (vs Hg/HgO), and the utilization ratio is over 98%.

Self-healing and corrosion protection performance of organic polysulfide@urea-formaldehyde resin core-shell nanoparticles in epoxy/PANI/ZnO nanocomposite coatings on anodized aluminum alloy

Coatings of epoxy resin blended with polyaniline (PANI)/ZnO nanocomposites and core-shell nanoparticles of organic polysulfide@urea-formaldehyde resin as self-healing agents have been prepared. The corrosion inhibition and self-healing performance of the scratched coatings on the anodized aluminum alloy (2024-T3) substrates in 3.5% brine at 65 °C were investigated. PANI/ZnO nanocomposite (1.3% ZnO) have been successfully prepared by in-situ emulsion polymerization of aniline in the presence of ZnO nanoparticles. The core-shell nanoparticles of organic polysulfide@urea-formaldehyde resin (60–80 nm) was synthesized via two microemulsions method. The materials were characterized by Fourier transform infrared (FT-IR) spectroscopy, dynamic light scattering (DLS), scanning electron microscopy (SEM) and thermal gravimetric analysis (TGA) techniques. The morphology of the coatings was studied by atomic force microscopy (AFM). Corrosion behavior of the coatings were investigated by electrochemical impedance spectroscopy (EIS). Finally, epoxy/PANI/ZnO coatings containing relative amounts of 0, 5, 7.5 and 10 wt% of the synthesized core-shell nanoparticles were fabricated on the anodized aluminum alloy and their electrochemical and self-healing behavior were studied. The coating with 7.5% core-shell have resulted to a much more superior corrosion protection than other samples, and also a significant self-healing response against the cracks exerted on the coatings.

Characterization and corrosion behavior of anodized Aluminum alloys for military industries applications in artificial seawater

The corrosion behavior of the hard anodizing coating layer, formed on Aluminum alloys in sulphuric acid electrolyte containing sodium lignin sulphonate, was investigated by using salt spray procedure and Potentiodynamic polarization technique, in 3.5% sodium chloride solution. The anodic process was performed on different groups of Aluminum alloys as Al2014, Al6061and Al7075, which are used in military industries. The results showed that the corrosion resistance and the anodized coating layer are influenced by the type of the alloy and the anodizing conditions such as current density, acid concentration and time of duration. Moreover, changes in film thickness, anodic coating weight and hardness of Aluminum alloys have been studied and the obtained results were compared and analyzed. Adsorption of sodium lignin sulphonate on oxide surface has been confirmed by Fourier transform infrared spectroscopy (FTIR). The phenolic and carboxylic groups in lignin inhibitor are responsible for forming a complex on the metal oxide surface, that improves the corrosion resistance.

Anticorrosive Performance Approach Combining an Epoxy Polyaminoamide–Zinc Phosphate Coatings Applied on Sulfo-tartaric Anodized Aluminum Alloy 5086

This study focused on developing an effective anticorrosive formulation for selected sulfo-tartaric anodized aluminium alloy (Al-alloy AA5086) to withstand harsh marine environment. The developed formulation was based on an epoxy resin bisphenol A diglycidyl ether (DGEBA) that is cured with polyaminoamide. Two sets of coated Al-alloy AA5086 samples were prepared using the epoxy resin formulation; a standard and ER–EZ. The formulation for making the ER samples included zinc phosphate (ER–ZP). Zinc phosphate was added to the formulation in about 5 wt%. The coated samples of Al-alloy AA5086 were evaluated by exposing them to a salt spray test chamber for various periods of time. The test was carried out according to an ISO 7253 standard test. The anticorrosive performance of the two epoxy coatings, the standard and ER–ZP were monitored by an electrochemical impedance spectroscopy (EIS). According to the EIS results, ER–ZP exhibited superior anticorrosive performance. The surface morphology analysis of the ER–ZP sample as shown by scanning electron microscopy with energy-dispersive spectroscopy (SEM/EDS) stayed smooth with minor roughness even after exposure to the harsh environments for 4392 h. The Bode and Nyquist plots showed that the ER–ZP coating has an outstanding barrier property in protecting Al-alloy AA5086 in marine environment against corrosion. The superior performance of the ER–ZP could be attributed to the presence of zinc phosphate which enhanced the adhesion properties of the coating and made it a more effective barrier.

Effect of NaAlO2 sealing on corrosion resistance of 2024 aluminum alloy anodized film

In order to effectively improve the corrosion resistance of aluminum alloys, anodic oxidation technique was used to generate the oxide film. Sealing after anodization is an important step to improve the corrosion resistance of aluminum alloys. In this paper, sealing effect of NaAlO2 solution on the oxalic acid anodized aluminum alloy was studied by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM), and X‐ray photoelectron spectroscopy (XPS). Experimental results show that unsealed anodized aluminum alloys display a porous structure and have poor corrosion resistance but the pores are filled and the corrosion resistance of the sample is significantly improved when anodized aluminum alloy was immersed in 0.2 m/L NaAlO2 solution with pH of 7 for 5 min at 85 °C. Moreover, the anodized aluminum alloy with NaAlO2 sealing exhibited better corrosion resistance compared to the hydrothermally sealed sample, because of the formation of more AlOOH in NaAlO2 sealing treatment.

Localized corrosion of aluminum alloy 6061 in the presence of Aspergillus niger

The corrosion behavior of anodized and non-anodized aluminum alloy 6061 in the presence of Aspergillus niger fungus was studied using electrochemical noise, recurrence plots and electrochemical impedance spectroscopy techniques. Corrosion potential measurements were also obtained. The fungus generated organic acids causing microbially induced corrosion of the specimens, which was more evident on non-anodized than on anodized aluminum alloy 6061, showing uniform and localized corrosion and a change in the attack as a function of the fungus growth time. A biomass growth curve was obtained to compare the behavior of anodized and non-anodized aluminum alloy 6061. A long-term electron transfer mechanism was proposed for localized corrosion of aluminum alloy 6061.

Electrochemical Degradation of Phenol and Resorcinol Molecules through the Dissolution of Sacrificial Anodes of Macro-Corrosion Galvanic Cells

This paper reports on the processes of phenol and resorcinol electrodegradation carried-out through continuous anodic dissolution of aluminum alloy and carbon steel sacrificial anodes for artificially aerated Cu-Al alloy and Cu-Fe-based galvanic (macro-corrosion) cells and synthetically prepared wastewater solutions. Electrochemical experiments were carried-out by means of a laboratory size, PMMA (Poly-methyl methacrylate)-made electrolyser unit, where significant degrees of phenol (10–89%) and resorcinol (13–37%) decomposition were obtained and visualized through the respective chemical/spectroscopy analyses. In addition, quantitative determination of phenol, as well as resorcinol (and possible electrodegradation products) for the selected experimental conditions was performed by means of instrumental high-performance liquid chromatography/mass spectrometry analysis.

Investigation of Electro-Thermal property for Cu-MWCNT composite coating on anodized 6061 aluminium alloy

In this paper, electrodeposition process was used for deposition of copper based multi-walled carbon nanotubes (MWCNTs) nanocomposite coating on 6061 aluminium in order to enhance the electrical and thermal properties. The method of anodization of aluminium alloy was applied prior to plating to get highly adherent Cu-MWCNT composite coating. Ammonium bi-fluoride (NH4F·HF), a fluorine-containing inorganic substances was added to the anodized solution to increase the porosity of the anodized aluminium alloy surface. Cetyl Tri-methyl Ammonium Bromide (CTAB) cationic surfactant was added in electrolytic bath to get stable, colloidal and uniform dispersed MWCNT copper sulphate solution. The characterization and compositional analysis of the developed Cu-MWCNT composite coating was investigated by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and x-ray diffraction (XRD). The electrical and thermal conductivity were measured for the pure copper coated and Cu-MWCNT nanocomposite coated samples, respectively. It was found that incorporation of MWCNTs in the copper coatings enhanced the electrical conductivity by 59.63%, 103.67% and 128.44%, respectively for Cu-MWCNT (0.5 gL−1, 0.75 gL−1 and 1 gL−1, respectively) nanocomposite coated specimens compared to pure copper coated specimen. The thermal conductivity of Cu-MWCNTs (0.5 gL−1) composite coated sample was improved by 95.62% compared to uncoated 6061 aluminium specimen.

Development of High Corrosion Resistance Hydrophobic Layers on Aluminum Immersed in Saline Geothermic Media

Anodizing processes are widely well-known processes to increase corrosion resistance and to modify the surface features of aluminum alloys. The anodizing parameters of aluminum such as electrolytes, applied current density and processing time in conjunction with the incorporation of a fluoropolymer compound were investigated to obtain thin and uniform layers of aluminum oxides resistant to saline geothermic media. The morphology of anodized films was assessed by using scanning electron microscopy. According to electrochemical impedance analysis, the incorporation of a FP to the anodized aluminum significantly increased the impedance resistance due to the formation of a hydrophobic layer on the surface of the anodized aluminum with high contact angle values. This hydrophobic processing was applied in an aluminum heat exchanger which is intended to be used in real geothermic conditions. The long-term corrosion resistance of the hydrophobic layer represents a good alternative to enhance the electrochemical properties of anodized aluminum alloys.

Galvanic Anodes for Reinforced Concrete Structures: A Review

In recent years, the use of sacrificial anodes for cathodic protection in reinforced concrete structures has increased, reflecting ease of installation, low-maintenance requirements, as well as desirability in prestressed concrete structures where the naturally controlled protection potential decreases the risk of hydrogen embrittlement. Zinc-based alloys have been among the most evaluated galvanic materials for concrete structures, especially in the United States, in many applications: thermal spray, superficial metal/mesh with and without hydrogel adhesive, embedded in concrete (point anodes) with or without salt activator, etc. However, the protection capacity lifetime of zinc alloys as used has been questioned based both on laboratory and on field application studies. Aluminum alloys have also been evaluated, sometimes showing better results as anode materials than zinc alloys. However, both zinc and aluminum alloy anodes may experience limited applicability in concrete structures exposed only to atmospheric conditions, as opposed to those in immersed, tidal, and splash zone service. This paper presents a review of the research work in the literature to date for both laboratory and field evaluations, toward identifying technically relevant situations where the use of sacrificial anodes may or may not be a practical option for reinforcement protection in concrete structures.

The footprint of surface modification treatments on the corrosion-fatigue of AA7075-T651

Different manufacturing and surface modification treatments distinctively affect the surface characteristics and microstructure of the workpiece, having a different impact on their effective life-span. The corrosion-fatigue behavior of as-machined (wire-EDM), blasted and anodized aluminum alloy 7075-T651 was investigated using 3.5wt% NaCl aqueous solution and distilled water as corrosive media. An in-situ corrosion-fatigue device capable of producing cyclic loads in a corrosive solution was employed, coupled with FEM analysis. Blasting process offered a prolongation of the corrosion-fatigue life-span in both corrosive media, when compared to the as-machined samples under identical conditions. Anodizing had a deleterious effect in all the examined cases.