Aluminum Alloy Substrate Research Articles

Influence of pretreatments on physicochemical properties of Ni-P coatings electrodeposited on aluminum alloy

Aluminum often requires protective coatings to prevent corrosion. The aluminum alloy substrate usually needs pretreatment to minimize, stabilize or convert the surface oxide in order to achieve adequate coating adhesion. The electrodeposited Ni-P coating is a promising candidate as a protective coating due to its easy fabrication and excellent performance. This study comprehensively investigates the pretreatment of zincating and anodizing on 6061 aluminum alloy, and systematically discusses their influence on the electrodeposited Ni-P coatings. The crystal structure and elemental composition were investigated for interlayers and Ni-P coatings subsequently, while morphologies of the coating surface and cross-section were also determined. The results revealed similar phase composition for differently pretreated Ni-P coatings, while distinct nodule featured morphology was observed for anodized Ni-P coating. It was found that anodized Ni-P coatings had the best performance due to its superior coating adhesion, wear-resistance, and corrosion resistance. In contrast, severe wear damage was occurred to zincated Ni-P coatings due to its inferior microstructure and weak zinc interlayer. Lastly, the influence of anodizing pretreatment on the coating microstructure is discussed, and a model is proposed for Ni-P electrodeposition employing anodizing pretreatment.

Study of Surface Properties in Laser Surface Alloying of AlxCu0.5FeNiTi High-Entropy Alloy

Due to better alloying characteristics, high-entropy alloys may result in superior surface properties. The present paper investigates the microhardness and erosion behavior of laser surface alloyed AlxCu0.5FeNiTi high-entropy alloy on aluminum alloy (AA1050) substrate. The effects of laser power, scan speed, and powder feed rate on microhardness and erosion rates are studied comprehensively. X-ray diffraction confirms the presence of a three-phase system and a shift in the peak at high power density, which indicates more significant lattice distortion. Scanning electron microscopy images show good dispersion of the three-phase system at optimum parameters. Energy dispersive spectroscopy confirms the presence of elements with negligible precipitation. Further, experimental data are used to develop empirical models. The optimizations of these models show an appropriate selection of parameter levels that may result in an erosion-resistant alloy. At optimum parameters, microhardness and erosion rate improve by 11.56 and 22.44%, respectively.

Electrodeposition of Paramagnetic Copper Film under Magnetic Field on Paramagnetic Aluminum Alloy Substrates

Electrodeposition of Paramagnetic Copper Film under Magnetic Field on Paramagnetic Aluminum Alloy Substrates

Microstructure and Properties of an Al 6061/Galvanized Plate Fabricated by CMT Welding

Aluminum alloy 6061 was welded with zinc coated low carbon steel by cold metal transfer (CMT). The microstructure composition, morphology and growth process of the welding joint and the HAZ were researched. The weld area on the side of the galvanized steel sheet mainly contains Fe2Al5. And on the side of the aluminum alloy substrate, it is mainly filled with a needle-like FeAl3. At the same time, Al8Fe2Si is formed at the edge of FeAl3. The zinc-rich region on the side of the aluminum alloy mainly contains an aluminum-zinc solid solution and an aluminum-zinc co-crystal, and the current size had no significant effect on the type and morphology of the compounds produced in the interface layer.

Synthesis and evaluation of a novel fluorinated poly(hexafluoroisopropyl methacrylate) polymer coating for corrosion protection on aluminum alloy

The hydrophobic and corrosion resistive film of cross-linked poly(hexafluoroisopropyl methacrylate) was successfully prepared by a simple photopolymerization method. The starting materials were a monomer of 1,1,1,3,3,3-hexafluoroisopropyl methacrylate, a photoinitiator of hydroxycyclohexyl phenyl ketone, and a cross-linker of poly (ethyleneglycol diacrylate). A very simple coating technique of drop-casting was used to deposit the fluorinated polymer onto an aluminum alloy substrate (AA 3003). The polymer coating was stable over a 60-day period when exposed to an aqueous solution of 3.5% NaCl as measured by open circuit potential technique. The fluorinated polymer coating had high corrosion protection when measured by potentiodynamic polarization with a reduction of 90% in the corrosion current density for the polymer-coated aluminum alloy over the bare substrate. The corrosion current density decreased to 0.065 μA/cm2 for the aluminum alloy coated with the polymer film compared to 0.708 μA/cm2 for uncoated aluminum alloy. Fourier-transform infrared spectroscopy was used to monitor the polymerization process. The dynamic contact angle technique was used to measure the hydrophobicity for the fluorinated polymer coating and increased from 65° to 100° for the uncoated and coated substrate, respectively. Contact angle measurements before and after treatment with strong acid were carried out to confirm the chemical resistance of the polymer coating. The thermal stability of the fluorinated polymer was measured using thermogravimetric analysis showing thermal stability up to 200 °C.

Wettability and Anti-Corrosion Performances of Carbon Nanotube-Silane Composite Coatings

In this paper, a sol-gel N-propyl-trimethoxy-silane coating filled with different amount of multi-wall carbon nanotubes (MWCNTs) was investigated in order to improve the aluminum corrosion resistance. The nanocomposite coating was applied, by drop casting, on AA6061 aluminum alloy substrate. The morphological analysis highlighted that a uniform sol-gel coating was obtained with 0.4 wt.% CNT. Lower or higher nanotube contents lead to the formation of heterogeneities or agglomeration in the coating, respectively. Furthermore, all nanocomposite coatings exhibited effective adhesion to the substrate. In particular, the pull-off strength ranged in 0.82–1.17 MPa. Corrosion protection of the aluminum alloy in NaCl 3.5 wt.% electrolyte (seawater) was significantly improved after CNT addition to the base coating. The stability in electrochemical impedance was observed during three days of immersion in the sodium chloride solution. AS3-CNT2 and AS3-CNT4 batches showed advanced electrochemical stability during immersion tests. Furthermore, interesting results were evidenced in potentiodynamic polarization curves where a decrease of the corrosion current of at least two order of magnitude was observed. Moreover, the breakdown potential was shifted toward noble values. Best results were observed on AS3-CNT6 specimen which exhibited a passivation current density of approximately 1.0 × 10−5 mA/cm2 and a breaking potential of 0.620 V/AgAgClsat.

Aluminum borophosphate glaze-coated aluminum alloy substrate: Coating properties and coating/substrate coupling

Thermal fatigue can cause irreversible damage in aluminum alloys restricting their use in the automotive industry, despite their excellent mechanical and technological properties. The application of ceramic coating is an alternative to obtain a protective barrier to improve the wear resistance at high temperatures. However, the low melting point and high coefficient of thermal expansion (CTE) of aluminum alloys limit the coating options. Thus, a suitable coupling feature can be obtained between aluminum alloys and a glazed coating. A glazed coating based on the aluminum borophosphate system was developed and applied onto an aluminum-silicon-copper commercial alloy. The coating was characterized by X-ray diffractometry, scanning electron microscopy, hardness tests, and thermal analysis. The coupling between the glazed coating and the aluminum alloy surface was studied employing optical dilatometry and optical fleximetry. A dense, good adhesion coating and presenting adequate dilatometric coupling (effective coupling temperature of 345 °C) related to the investigated aluminum alloy was obtained at 500 °C. The good compatibility of CTE between the layers (24.54 × 10−6 °C-1 for the substrate and 14.56 × 10−6 °C-1 for the coating) led to a crack-free material. For this reason, microhardness increased from 136 (aluminum alloy) to 325 HV (glazed aluminum alloy). The glazed coating can expand the use of this alloy, improving its performance and thermal efficiency. This result suggests an enormous potential of applications in the automotive industry, for instance.

RETRACTED ARTICLE: Silver Nanoparticles Intercalated Polyaniline Composites for High Electrochemical Anti-Corrosion Performance in 6061 Aluminum Alloy-Based Solar Energy Frameworks

In this work, we report on polyaniline (PANI)–silver nanoparticles (AgNPs) coatings prepared by in-situ polymerization technique. These composites show an excellent corrosion resistance behavior in aggressive environments much superior to PANI. The corrosion studies were carried out on 6061 aluminum alloy substrates coated with PANI-AgNPs composites with different concentrations of silver nanoparticles. The PANI-AgNPs composites were characterized by Scanning and Transmission electron microscopes (SEM/TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Thermogravimetric analysis (TGA). The conductivity of these composites strongly depends on AgNPs concentration with percolation maxima at 20 wt% of AgNPs in PANI. The composite coatings were evaluated for anti-corrosion performance by using standard corrosion testing method, open-circuit potential analysis, potentiodynamic polarization curve, and electrochemical impedance spectroscopy. The increase in diffusion barrier, prevention of charge transport by the AgNPs, redox properties of polyaniline as well as the large surface area available for the liberation of dopant due to nano-size additive appear to be associated with the exceptional improvement in anti-corrosion performance of elaborated coatings. Due to ease of preparation, better thermal stability, enhanced conductivity, and excellent corrosion inhibition properties, this PANI-AgNPs composite could be used as a potential anti-corrosion coating material in protecting aluminum infrastructures.

LASER SURFACE REINFORCEMENT OF THE Ti/Al TIG WELDED JOINT

The microstructure of the Ti/Al weld seam (WS) was uniform, and a good metallurgy bond between TC4/5052 aluminum alloy substrates was obtained without obvious defects after the Tungsten inert gas (TIG) process. Then, a remelt layer (RL) with fine microstructure can be formed by means of a laser remelting (LR) technique of the Ti/Al TIG joints. The Ti–Al intermetallics were produced adhered to the weld joints’ surface, exhibiting the extreme high surface hardness. The micro-hardness distribution of this RL surface was in a range of 1150–1200 HV[Formula: see text], which was significantly higher than that of the TC4 titanium alloy substrate. The high micro-hardness of the weld joints’ surface can be mainly ascribed to the actions of the Ti–Al intermetallics, the fine grain and the solid solution strengthening.

Brazing diamond grits onto AA7075 aluminium alloy substrate with Ag–Cu–Ti filler alloy by laser heating

The brazing of diamond is a promising way to fabricate grinding wheels for efficient machining and precision grinding. This work investigated the feasibility of bonding diamond grits onto Aluminium Alloy 7075 (AA7075) substrate with a Ag–Cu–Ti filler alloy via laser fusion brazing. The interfacial microstructures and the strength of the brazed diamond joints were studied. The cross-section of the brazed diamond joint consists of a molten filler alloy layer, a molten pool, a heat effect zone, a columnar crystal zone and an equiaxed crystal zone. Within the interface of the filler alloy/substrate metal, microstructures observed possibly were Ag(s.s), Al(s.s), TixAl, Al2Cu and Mg intermetallic compounds. A layer of TiC with a thickness of about 30–50 nm was found at the bonding interface of the diamond/filler alloy. The averaged peak shear force of the brazed joints was found to be approximately 39.8 N. The abrasion grinding test indicated that the diamond/AA7075 brazed joint was adequate for grinding. However, the pulled-off of grit was found to be the primary failure of this type of brazed joint. This work broadened the brazing diamond technique and the range of applications of brazed diamond wheels for efficient grinding.

Study on the characteristics and mechanism of pulsed laser cleaning of polyacrylate resin coating on aluminum alloy substrates.

The behavior of paint removal with a pulsed laser has been investigated using an Nd:YAG fiber laser. Experimental and theoretical analyses are conducted to reveal the underlying mechanism of the paint removal. The results show that the depth, radius, and volume of the pit formed by a single pulse become larger with increases in the energy density. The ideal parameters for the complete removal of paint have been achieved. During the paint removal, burning occurred over the surface, and the variation in element content has been attributed to the absorption of laser energy. Under the action of the pulsed laser, there was breakage and rearrangement of chemical bonds such as C-C, C-N, and C-O in the molecular chain of the polyacrylate paint coating. Through these analyses, the paint removal mechanism was shown to be based on chemical bond breakage, combustion, and mechanical action provided by the thermal expansion and plasma shock.

Green hybrid zeolite coatings for on-orbit molecular decontamination

FAU-type and MFI-type green hybrid zeolite coatings were developed for on-orbit molecular decontamination application by using a mixture of an organic binder (silicone resin) and an inorganic binder (suspension of colloidal silica nanoparticles). The zeolite content in the final dry coatings varies from 80 to 85 wt % whereas the total amount of binders varies from 15 to 20 wt %. This amount of binder was sufficient to give the zeolite coating interesting adhesion and cohesion properties. In fact, by using an equal amount of each binder, homogeneous films without significant cracks were obtained on an aluminum alloy substrate which is the main constituent of satellites. Nitrogen adsorption-desorption measurements revealed almost no loss of micropore volume of zeolite coatings. Adsorption experiments of an organic pollutant were carried out using n -hexane as probe molecule. The n -hexane adsorption capacities of FAU-type hybrid zeolite coatings (136–143 mg/g anhydrous zeolite ) are lower than that of pure FAU-type zeolite (180 mg/g anhydrous zeolite ) due to water co-adsorption. The n -hexane adsorption capacities of MFI-type zeolite coatings (103–106 mg/g anhydrous zeolite ) are similar to that of pure MFI-type zeolite (110 mg/g anhydrous zeolite ). • Hybrid zeolite coatings were developed with high zeolite contents (80 and 85 wt %). • A combination between an organic binder an inorganic binder was studied. • Good adhesion properties of zeolite coatings on an aluminum alloy substrate. • Interesting adsorption capacities of n -hexane by zeolite coatings. • Potential applications for VOCs adsorption.

Fabrication of robust superhydrophobic Ni–SiO2 composite coatings on aluminum alloy surfaces

Artificial superhydrophobic surfaces have attracted increasing research interest due to their self-cleaning properties. However, their poor corrosion and temperature resistance restrict their extensive applications. In this study, an electrodeposition method was employed to fabricate a robust superhydrophobic Ni–SiO2 composite coating with temperature resistance, corrosion resistance, adhesion strength, and wear resistance properties on an aluminum (Al) alloy substrate. The Ni–SiO2 composite coating was found to have high hardness by using a hardness indenter with a load of 1000 g. The temperature resistance was investigated by rapid temperature cycling from 100 °C to −35 °C. Corrosion resistance to acidic and alkaline environments was also presented. Adhesion strength, wear resistance, robustness, and flexibility were tested to show the stability of the coating. The proposed approach for fabricating robust superhydrophobic Ni–SiO2 composite coatings shows great potential for industrial applications.

Cooperative and synergistic corrosion inhibition of AA 7075-T6 by praseodymium and CaSO4

Abstract In a primer coating system used in aerospace applications to protect aluminum alloy substrate, praseodymium is added as corrosion inhibitors while CaSO4 is primarily added as filler materials. The interaction of Pr and CaSO4 is unknown. The goal of this study is to characterize any cooperative or synergistic inhibition between these two. Cooperative inhibition can be defined when one inhibitor enhances inhibiting effect of the other that already has inhibiting ability. Synergistic inhibition can be defined when one inhibitor activates the inhibiting effect of the other that originally does not inhibit. Optical profilometry, electrochemical techniques and X-ray photoelectron spectroscopy were used to characterize corrosion results. The results showed that several pit parameters will affirm the inhibition effect. Electrochemical results cannot always detect modest corrosion inhibitors. Cooperative inhibition was detected in pH 5 while synergistic inhibition was observed in pH 8. Synergistic inhibition occurs because SO4 2− helps with gelation of Pr to passivate the surface.

Thermal barrier coatings formed by flame-spray with metal–EDTA

Nowadays, the selection of a suitable spray method to design the coating microstructure such as its porosity, is key to effectively improving the properties of the base materials. In this study, the microstructures and thermal insulation capability of chelate flame-sprayed erbium oxide (Er2O3) and yttrium oxide (Y2O3) coatings directly deposited on aluminum alloy (A5052) substrates were investigated. A rotation apparatus and cooling agent (liquid nitrogen) were used during the synthesis to cool the substrate and control the deposited particles’ shape or form during film deposition. The results show that the Y2O3 coatings had higher thermal insulation capability than the Er2O3 coatings. It is worth noting that the thermal insulation capacity of the Y2O3 and Er2O3 coatings synthesized by cooling the substrate with liquid nitrogen was improved. For thicknesses of 90–128 μm and cross-sectional porosities of 12%–33% of the Y2O3 coatings, a temperature drop (ΔTf = 37 °C) of the porous structure Y2O3 coating at 440 °C and an increase from 0.10 to 0.32 of ΔTf per unit micron (°C μm–1) were observed. This was due to the coating having a more undulated layer surface and more complicated microstructures. Therefore, it is a new idea with the chelate flame-spray method to synthesize thermal barrier coatings on low-melting-point-metal materials.

Reaction Behavior, Microstructure, and Radiative Properties of In Situ ZrB2-SiC Ceramic Composites from a Si-Zr-B4C System

The present work focuses on the in situ self-propagating high-temperature synthesis (SHS) of ZrB2-SiC (ZS) ceramic composites in a Si-Zr-B4C system. The reaction process characteristics, microstructure and radiative properties of products were investigated. The thermal conductivity of ZS/acrylic composite coating filled with 40 wt.% ZS is 1.77 W/m K, which is ninefold enhancement in comparison with neat acrylic coating. In addition, in situ ZS/acrylic composite coatings showed an excellent increase in infrared emissivity up to 0.93 for 45 wt.% in situ ZS content, which was nine times more than bare aluminum alloy substrate. The produced coatings remarkably increased the heat dissipation performance of an aluminum alloy tube by 17.9%, implying a promising prospect for real passive heat dissipation applications.

Hypergyrating Droplets Generated on a Selective Laser-Textured Heterogeneous Wettability Surface.

An impacting droplet on water-repellent surfaces experiences spreading, retraction, and bouncing phases, among which the spontaneous droplets gyrating is very interesting and has promising applications. Here, we present an ultrahigh-speed gyrating droplet generation method via torque transmission on a heterogeneous wettability surface. Hybrid superhydrophobic-superhydrophilic (SH-SHL) patterns were fabricated by selective laser texturing on aluminum alloy substrates. The maximum static contact angles (CAs) of the SH region and SHL region were 163.3 ± 2 and 0 ± 1°, and the advancing and receding CAs were 162.2 ± 1 and 159.9 ± 1°, respectively. The hybrid SH-SHL pattern coupling with the translational kinetic energy of impacting droplet and the rotational momentum of the rotating substrate has been proved as a high-efficiency energy conversion method to construct hypergyrating droplets. A hypergyrating speed exceeding 96 700 rpm (13 times of the latest reported value) was achieved in droplets impact on the hybrid SH-SHL-patterned heterogeneous wettability surface, and the maximum energy transformation ratio (α) of the rotating specimen driven torque to the rebounded gyrating droplet is 83.40%. The regulation of the maximum gyrating speed of a bouncing droplet could be controlled by the pattern size and the substrate driving speed, which suggests a practical approach in the energy transformation, a new type of cleaning strategy, and other industrial applications.

Multiscale corrosion analysis of superhydrophobic coating on 2024 aluminum alloy in a 3.5 wt% NaCl solution

Abstract

Enhanced Tribological Performance of a Ni/GO-Coated 2024 Alloy

Due to its advantages of light weight, high specific strength, large drilling depth and low energy consumption, 2024 Al alloys can potentially be used in drill pipes. However, their poor wear resistance restricts further development. In this paper, graphene oxide (GO) was prepared by the Hummer’s method. A Ni/GO composite coating was deposited by electroplating onto a 2024-t6 aluminum alloy to improve its wear resistance. The morphology and phase of the Ni/GO coating were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and x-ray diffraction (XRD), and the surface hardness, wear volume and friction were tested. The wear test results show that the friction coefficient of the Ni/GO composite coating was the smallest, the wear scar was the shallowest, and the wear volume was the lowest compared with those of the Ni coating and aluminum alloy substrate. The wear scars observed with SEM revealed that the wear spot of the composite coating was obviously less than that of the Ni coating under the same load. It was concluded that the wear resistance of an aluminum alloy matrix can be greatly improved by a Ni/GO composite coating.

Wettability, durability and corrosion properties of slippery laser-textured aluminum alloy surface under water impact

Laser textured aluminum alloy substrate was sprayed with hydrophobic SiO2 nanoparticles followed by the infusion of perfluoropolyether oil. The wettability and the corrosion properties were evaluated before and after the continuous water droplet impact tests. The results showed that the formation of composited pores consisting of micron-sized textured dimples and nano-sized porosities helps in enhancing the preservation of perfluoropolyether oil. The integration of textured micro-dimples endows durable water-repellency to the oil-infused SiO2 nanoparticle coating and the water contact angle stabilizes at a level of about 130° after the water droplet impact of 30 h. The micro-nano composited pores acted as oil reservoirs effectively prolong the life of lubricating oil layer, resulting in a superior corrosion resistance showing neither cathode nor anode currents against water droplet impact for 15 h.