Papers by Keyword: Anodizing

Abstract: The Mg-1wt.%Ca alloy was fabricated using powder metallurgy method. The anodizing process were done by using different voltage (5V, 15V, 25V) and concentration of KOH (0.1M, 0.5M, 1.0M). The surface changes on PM Mg/1wt.%Ca resulted by anodizing was analyzed using SEM-EDX and XRD pattern. Meanwhile, surface hardness was measured by micro-Vickers hardness machine. The experiment found different XRD pattern between all non-anodized and anodized samples. The study found that increasing the voltage will increase the hardness while increasing KOH concentration reduced the hardness. The relation of the hardness and oxide film formation can be analyzed using SEM-EDX and XRD pattern. The optimum value for voltage, KOH concentration and hardness are 25V, 0.1M and 27.2 HV. The XRD detect the changes in PM Mg/1wt.% Ca indicates the oxide film formation.

Abstract: Bioabsorbable magnesium (Mg) alloy was anodized in 1.0 M NaOH solution to improve the corrosion resistance. Then the anodized Mg alloy was immersed in an aqueous solution with three times of Ca²⁺ and HPO₄^2- and lower Na⁺ and Cl^- in comparison with those of conventional SBF. The whole surface of Mg alloy was successfully coated with plate-like apatite within 1 day. The thickness of apatite layer formed on Mg alloy was about 7 μm.

Abstract: Titania nanotube arrays were formed by electrochemical anodic etching of titanium from glycerol solutions with addition of 0.5% HF and analyzed by scanning probe microscopy and ellipsometric analyzes. Potentiostatic curves allow identifying several different stages of growth of nanotubes of titanium dioxide, however, this method does not establish specific parameters of the surface. We demonstrated that analysis of the spectrum ellipsometric parameters Psi and Delta can used as a criterion of quality, frequency, depth and other characteristics of the obtained arrays of titania nanotube. The use of these methods of analysis allowed to fully characterize the different stages of growth of titania nanotube from glycerol solutions and can be used for quality control the resulting structures for various applications.

Abstract: High-strength magnesium alloy (AZ31) reinforced poly-lactic acid (PLA) composite rods for potential application of bone fracture fixation prepared by plastic injection process on Mg rod.Thecomposities possess improved the interfacial bonding between poly-lactic acid and Mg rod due to the micro-anchoring which lead to better mechanical performance in Simulated body fluid solution.The present results indicated that this new PLA-clad Mg composite rods show good potential for biomedical applications.

Abstract: Anodization is an electrochemical process that converts the metal surface into a decorative, durable, corrosion-resistant, anodic oxide coatings. The thickness of the resulting layer depends on the process parameters (voltage, current, type of electrolyte, concentration and temperature of the electrolyte). In this work, the preparation of zinc metallographic samples with anodic layer is described. Samples prepared by anodic oxidation on the zinc substrate are rather brittle and porous. During the mounting, cutting, grinding and polishing the layer can be deformed which can affect the layer thickness measurements. The problem is to determine the boundary between anodic layer and resin. The cross-sectional micrographs were observed by scanning electron microscopy with the aim to improve anodic layers thickness measurements by means of digital image analysis.

Abstract: Electrochemical process of conversion coatings formation on Zn-Ti alloy surface during one-step anodizing process was studied in NaOH and KOH electrolytes over the range of voltages (4-50 V) and constant time in order to investigate parameters for the origin of anodic zinc coating. Stainless steel was used as a counter electrode and electrolyte during the anodizing process was agitated by compressed air. Coatings microstructures and morphology were characterized by means of scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). Surface topography was investigated prior and after the anodizing using non-contact optical 3D profilometer. It was found that high voltage (50 V) and low concentrations of electrolyte (0.04 and 0.1 mol/L NaOH) led to origin of white coloured oxide coatings, while lower voltage (4 and 6 V) and higher concentrations of electrolyte promote the origin of black coloured oxide coatings. Concentration of electrolyte and voltage influenced the thickness of conversion coatings and its surface morphology. Moreover, the surface morphology of the coatings was also influenced by the heterogeneity of substrate alloy.

Abstract: The effect of hydrothermal treatment time on sealing and corrosion resistance of the AA7475-T761 anodized aluminium alloy has been investigated in this study. The hydrothermal treatments tested are environmental compatible without chromium ions involved. Anodizing was carried out by a tartaric-sulphuric anodizing (TSA) process and this was followed by hydrothermal treatments for partial sealing, in various solutions. The effect of propyleneglycol (PRG) and/or cerium ions in the hydrothermal treatment solution was evaluated. Four treatment times were tested, specifically, 2.5, 5.0, 7.5 and 10 min. The corrosion resistance of the anodized and treated samples was evaluated by Electrochemical Impedance Spectroscopy (EIS) and the anodic layers formed were characterized by Scanning Electron Microscopy (SEM). The EIS results showed that the hydrothermal treatments in solutions with cerium ions resulted in similar impedances for periods of treatment from 5 to 10 min whereas in the solutions with PRG the impedance increased with time of treatment from 2.5 to 10 min showing a slower kinetics of anodic layer sealing. However, the fastest kinetics of sealing were associated to the treatments that combined two steps, one in PRG and other in cerium containing solutions with similar impedances obtained from 2.5 to 10 min of treatment. Surface evaluation by SEM showed that the porosities in the anodic layer were not sealed for the periods of hydrothermal treatments corresponding to 2.5 min. The presence of cerium in hydrothermal treatment had a beneficial effect on the stability of the anodic layer formed and provided a healing effect on the corroding sites.

Abstract: This paper provides an overview of the main issues related to the durability of aluminium alloy structures. In particular, the main corrosion pathways are considered, in relation to alloy type, microstructural features, thermomechanical treatments and environmental characteristics. The strategies for corrosion mitigation are also discussed, with particular focus on the tailoring of anodizing treatments for enhanced durability.

Abstract: Anodizing is a surface modification technique that is applied to growing oxide films on Ti to accelerate the osseointegration of an implant. Besides the surface roughness, the crystalline structure of these films can affect its performance as a biomaterial. For this reason, this technique has been refined to produce crystalline films without requiring heat treatments. For this purpose, TiO₂ films were grown on Ti (grade 2) by anodizing with direct current at different potentials. Images obtained by optical microscopy with polarized light revealed a granular microstructure in various colors, as consequence of different crystalline orientations of the grains and films thickness. Raman spectroscopy showed that the films crystallinity is affected by variations in the applied potential and anodizing time.

Abstract: In this study, the inhibitor effect of Solidago chilensis extract as green corrosion inhibitor for anodized aluminum alloy samples was evaluated in NaCl 3%wt solution. This study was carried out for application on cans for pack of foods. The procedure of the surface treatment of the samples was done by anodizing followed by sealing in a solution containing the inhibitor. Essays of potentiostatic polarization and electrochemical impedance spectroscopy were done to evaluate the inhibitor effect. The mechanical analyses were performed on anodized samples to evaluate the influence of the thickness of anodization on the mechanical resistance of the samples. The potentiostatic essays indicated that a cathodic inhibitor effect occurs only in non-anodized samples and that the anodic effect of the inhibitor not appears on the anodized samples. The calculated efficiency of the inhibitor was 96 %. The EIS results indicated that the higher values of polarization resistance (16 kΩ) occur on anodized samples containing inhibitor after 72 hours of immersion in NaCl 3%wt. The mechanical essays indicated a non – significant difference between anodized and non – anodized samples.