Papers by Keyword: Anodic Oxide Film

Abstract: This work investigated the effects of sealing agents on properties of 7075 slurry cast substrate anodized in 1M sulfuric acid solution. The sealing agents tested were hot water, potassium dichromate, teflon, and nickel fluoride. It was found that anodized 7075 slurry cast Al oxide film sealed with teflon gave the highest hardness and the best corrosion resistance. It is possible that the porous oxide film was plugged by teflon, reducing porosity more than hot water, potassium dichromate, or nickel fluoride sealing.

Abstract: This research focused on the effect of solution heat treated microstructures on anodic oxide formations of casting 7075 Al alloy. The casting specimens were solution heat treated at 450°C for various holding. The results showed that the quality of anodic oxide film on the specimen with 4h solution heat treatment time was higher than that of at other conditions. Because its microstructures obtained the lowest amounts of secondary phase particles leading to improve the quality of oxide film and also reduce defects in oxide film. On the other hand, coarse black particles of Mg₂Si formed increasingly in microstructures of specimens after solution treatment at prolong holding time of 8h and 16h resulted in discontinues oxide films forming on them.

Abstract: Anodic oxide film on titanium alloy (Ti-6Al-4V) substrate was prepared by anodization. The reaction was done by applying low current densities from 0.25 to 2 mA/cm² for 30 minutes using monocalciumphosphate monohydrate (MCPM) solution as an electrolyte. Essential parameters which affected to the formation of anodic oxide film were studied. The properties of the anodic oxide film would be optimized when the parameters were appropriately controlled. Increasing of the current density and the concentration of MCPM electrolyte could promote hydrophilicity and surface roughness of the film. After anodization, the anodic oxide film formed at 2 mA/cm² in 1M MCPM showed the best hydrophilicity (lowest water contact angle) and the film formed at 0.25 mA/cm² in 0.5M MCPM showed the lowest hydrophilicity (highest water contact angle). XPS analyses confirmed that the chemical species of as-anodized film formed at 2 mA/cm² in 1M MCPM changed. Ti2p spectra scarcely changed while the O1s spectra significantly changed due to the presence of chemisorbed water and Ti-OH formed during anodization. The SEM micrographs also revealed the biocompatibility from the growth of the cementoblast cell on anodized surface. It was indicated that anodization using MCPM as an electrolyte at 2 mA/cm² in 1M MCPM could modify the surface roughness and chemical species and that both are likely to be crucial key factors for enhancing of hydrophilicity of as-anodized film which would enhance the biocompatibility of Ti-6Al-4V as a result.

Abstract: Anodic oxide films were prepared firstly on the surface of a 2024 aluminum alloy. Then the effect of different heat-treatment temperatures on the structure and properties of the films was studied. The results indicate that the construction units of Al2O3 oxide film were composed of tubules less than 100nm in external diameter, and the film became more compact and uniform as a result of the increased temperature after the heat treatments of 100, 150, 200, 250, 300, 350, and 400°C under the protection of a H2 atmosphere. The hardness of the films increased linearly with the increase of heat treatment temperature; whereas the wear loss tended to decrease first and then increase. After being treated at the temperature of 250°C, the hardness reaches 606HV, the wear loss is a minimum of 11mg. The structure of the film heat-treated at 250°C has a compact structure, higher hardness, and the best wear resistance.

Abstract: The matrix of AZ91D Magnesium alloy can be covered with a coat of protective film through anodic oxidation treatment, it’s able to make certain that the optimal surface combination properties are generated especially on corrosion resistance. This thesis is devoted to the research on forming process of anodic oxide film of AZ91D magnesium alloy; the experiment shows the formation of anodic oxide film at constant pressure is accompanied by precipitation of gases and fluctuation of current, XRD indicates that anodic oxide film is composed of MgO、γ-Al2O3 and a small amount of Si.

Abstract: The corrosion behavior of the anodic oxide film on aluminium 7A04 alloy is investigated in current paper, where the different anodic oxide films are prepared. Morphology observation on different anodic films is carried out by using laser confocal microscopy (LCM) and copper sulfate test. Meanwhile, the electrochemical properties are evaluated through using electrochemical impedance spectroscopy (EIS). The LCM observation shows that the anodic oxide film formed in boric/sulphuric mixed acid is uniform with porous appearance, while the anodic oxide film formed in chromic aid is nonporous one but defective. The copper sulfate test results show that the corrosion regions almost developed from micropores in strong corrosive media. The evaluation of EIS in NaCl solution demonstrates that the corrosion resistance of specimen with anodic oxide film is much better than that without film. Furthermore, the corrosion resistance of anodic film formed in boric/sulphuric mixed acid is better than that formed in chromic acid.