Al-Zn Alloy Formation by Aluminium Underpotential Deposition from AlCl+NaCl Melts on Zinc Substrate (original) (raw)
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Journal of the Serbian Chemical Society, 2019
Contrary to the widely accepted hypothesis that it is not possible, aluminum underpotential deposition (UPD) onto zirconium from a low temperature (200, 250 and 300 °C) equimolar chloroaluminate melt was recorded. Furthermore , it was shown that aluminum UPD facilitates alloy formation between the deposited aluminum monolayer and the zirconium substrate by interdif-fusion. The aluminum/zirconium alloys formed at temperatures substantially lower than those needed for thermal preparation of the same alloys were Al 3 Zr 2 and Al 3 Zr. The experimental techniques linear sweep voltammetry, potential step, scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction were used for the characterization of the obtained electrode surfaces.
Reinvestigation of nucleation and growth of Zn on Al surface during modified alloy zincating
Surface and Coatings Technology, 2019
Modified alloy zincate (MAZ) is a surface-treatment process for depositing Zn on Al by galvanic displacement reaction prior to application of functional coatings. Two-step zincating i.e. double zincating (DZ) is a preferred technique in comparison to single zincating (SZ) because of imparting excellent adhesion of coatings on Al. Prior to second step of zincating during DZ, the single zincated Al substrate undergoes nitric dissolution. In this study, the intriguing role of this nitric acid etching on second step nucleation and growth of Zn has been investigated in detail. For this, time dependent Zn-nucleation and growth morphology on Al surface was monitored by AFM and FESEM examinations and revealed scattered but coarse nucleation during SZ; and finer nucleation along with uniform coverage of Zn during DZ. Post single zincating, nitric acid etch led to generation of micro/nanoporous Al surface as revealed by microscopic investigations. The porous Al surface along with trace amount of noble metals such as Cu and Fe was found to play significant role on Zn root growth into Al matrix and fine grain Zn deposit on top surface confirmed by cross-section FESEM analysis of focused ion beam (FIB) cut Zn/Al sample. Rutherford Backscattering Spectroscopy (RBS) was used as a non-destructive technique to estimate Zn film thickness and growth rate. The observed Zn nucleation and growth results were further substantiated by analyzing the open circuit potential (OCP) data during zincating. Difference in nucleation and growth pattern of Zn on Al surface during SZ and DZ was fundamentally understood with the help of classical nucleation theory and galvanic kinetics.
Electrochemical Behaviour of Pure Aluminium and Al–5 %Zn Alloy in 3 % NaCl Solution
The effects of both immersion time and temperature were investigated to examine the electrochemical anode characters of pure aluminium and Al-5 %Zn in 3 % NaCl solution. Open circuit potential (OCP), linear polarization resistance (R p ), potentiodynamic polarization, electrochemical impedance spectroscopy techniques and Evans diagrams were used to characterize the electrochemical behaviour of the studied pure aluminium and Al-5 %Zn alloy. The materials surface was observed by means of scanning electron microscope. Whatever the studied temperature and the immersion time are, the Al-5 %Zn alloy induced a considerable activation compared to pure aluminium by shifting the OCP toward the negative direction and by a significant increase of the anodic current densities. Arrhenius relation between corrosion current densities and the inverse of temperature shows that the anodic oxidation of the Al-5 %Zn alloy is more spontaneous than that of pure Al. The Al-5 %Zn alloy coupled to the carbon steel leads to a better protection than the pure aluminium.
Surface and Interface Analysis, 2018
AA 3XXX alloys are widely used in heating, ventilation, and air conditioning (HVAC) field. Diffusion joining using a filler metal together with flux is employed in some applications as for heat exchangers. In this work, the effect of diffusion of a Zn-based flux on both microstructure and electrochemical behavior has been investigated. In particular, an AA3xxx was coated with a Zn-rich flux and subjected to controlled atmosphere brazing (CAB). Glow discharge optical emission spectroscopy (GDOES) composition profiles were acquired in order to determine the Zn distribution in the diffusion layer. The GDOES was also employed to produce a controlled erosion of the surface in order to obtain craters with defined depths in the Zn diffusion layer, in which electrochemical analyses could be performed. The Volta potential maps at different depths in the Zn diffusion layer were obtained by scanning Kelvin probe force microscope (SKPFM). The Zn diffusion layer was also investigated by means of Scanning Electron Microscope-Energy Dispersive X-ray Spectroscopy (SEM-EDXS) and the chemical composition of the phases present in the regions was investigated by SKPFM. Finally, the electrochemical microcell was used in the produced craters in order to determine the electrochemical behavior along the Zn diffusion profile. SKPFM and microcell results showed a correlation between the Zn content and the electrochemical properties. In particular, a higher Zn content in the diffusion layer leads to an increase of the Volta potential difference between the intermetallic particles and the matrix. The electrochemical measurements also showed that the Zn diffusion layer provides galvanic protection to the underlaying aluminum alloy.
Electrochemical Growth of Ag/Zn Alloys from Zinc Process Solutions and Their Dealloying Behavior
ACS Sustainable Chemistry & Engineering, 2022
This study investigates the sustainable preparation of Ag/ Zn alloys from a simulated zinc process solution (20 ppm Ag, 65 g/L Zn, and 10 g/L H 2 SO 4) via electrodeposition-redox replacement (EDRR) and the electrochemical dealloying behavior of the Ag/Zn alloys. Results indicate that Ag/Zn deposits with diverse compositions and microstructures can be obtained at room temperature without any complexing agents, simply by varying EDRR parameters like deposition time, deposition potential, and redox replacement time. Two types of Ag/Zn intermetallics (Zn 0.96 Ag 0.04 and Ag 0.76 Zn 0.24) were identified by the combination of X-ray diffraction (XRD) and anodic linear sweep voltammetry. Mass-transfer limitations have significant effects on the growth process, and a nucleation-growth mechanism from Ag/Zn particles into dendrites with increased EDRR cycles is introduced: with EDRR parameters favoring mass-transfer limitations (higher overpotentials, longer deposition times, and shorter redox replacement times), a more dendritic morphology of Ag/Zn alloys is achieved. The selective dissolution of Zn (i.e. dealloying) allowed the formation of silver-rich surfaces with an enhanced surface plasmon resonance behavior, which can be readily tuned by EDRR and dealloying parameters. These results highlight the significant potential of the EDRR-dealloying route to produce different types of Ag/Zn alloys and optically functional materials directly from base metal process solutions.
Development of Aluminum-Zinc Alloy by Adding Zn Solid and Zn Powder
Aluminum is most versatile material for various application like Aerospace, Marine and Transport industry due to high strength to weight ratio. Aluminum is alloyed with various element like copper, magnesium, zinc and silicon to obtain desired properties among which 7xxx (Al-Zn) series exhibits outstanding properties. This paper present idea to developed Al-Zn alloy by adding Zn in solid as well as powder form. Aluminum is doped with 1%, 3% and 5% Zinc by weight percent in both form. We get highest recovery in case of solid. Addition of Zn is also evaluated by hardness, tensile strength value and electrical conductivity. Superior properties are obtained in case of Zn solid.
Effect of Zn content on tensile and electrochemical properties of 3003 Al alloy
The effect of Zn addition on the microstructure, tensile properties and electrochemical properties of as-annealed 3003 Al alloy was investigated through TEM observations, tensile tests and Tafel polarization analysis. High density precipitates are observed in the Zn-containing alloys and the alloy with 1.8% Zn addition also has rod-like precipitates. Tensile test results indicate that Zn has a great effect on tensile strength of 3003 Al alloy. The alloy with 1.5% Zn addition has the highest ultimate tensile strength. The electrochemical results indicate that Zn addition to 3003 Al alloy also has great impact on the corrosion potential of the 3003 Al alloy in 0.5% NaCl solution and ethylene glycol-water solution. The corrosion potential varies with the Zn content and shifts negatively.
Aluminum–aluminum compound castings by electroless deposited zinc layers
Journal of Materials Processing Technology, 2014
Sandblasted aluminum sheets (Al 99.5) were coated with a basic zincate solution and integrated into high pressure die casting components (AlSi9Cu3(Fe)) with wall thickness ranging from 3 mm to 6 mm. Investigations of the Al-Al-interface showed that sound castings could be realized. Microprobe analysis was used to elucidate the dissolution and diffusion of the Zn coating as a function of the processing parameters. Due to the very small total amount of zinc we did not find a zone of brittle intermetallic phases at the interface. Shear testing of the compounds confirmed the presence of a firmly bonded compound without embrittlement by intermetallic phases.
Study of Directional Solidification of Zn-Al Alloys
Procedia Materials Science, 2012
Directional growth of Zn-Al alloys of different concentration was carried out by using a Bridgmann like apparatus. The compositions of studied systems were a) dilute Zn-0,5 wt.%Al, below the maximum solubility limit, b) hypo-eutectic Zn-2 and 4 %wt. Al, and c) hyper-eutectic Zn-8wt.% Al. Proper metallographic analysis of the segregation patterns behind the solid-liquid (S-L) interface gives information about the effect of the local solidification conditions to obtain different microstructures. It was found that the dilute alloy grows in a similar fashion than other alloys with atomistically rough interfaces. For alloys with composition above the maximum solubility limit, it was found that a single primary phase grows surrounded by liquid eutectic. In the case of hypo-eutectic alloys, a dendritic hcp primary phase is formed, whilst for hyper-eutectic alloys, the primary phase is an fcc Al-rich dendrite. In both cases, a secondary interface for eutectic solid-liquid is formed below the dendrite tips, in such a way the eutectic seems to growth independently of the primary phase.