anodizing

In this research, super-hydrophobic surfaces were made on pure aluminum (92%) using two methods of chemical etching, and onestep anodizing and modification with materials with low surface energy. After creating a uniform roughness on the surfaces, surface modification was done with perfluoroactyltrichlorosilane (PFTS). The wettability was investigated by measuring the drop contact angle (WCA) and the morphology of the coating with a field emission scanning electron microscope (FESEM). The chemical composition of the surface was detected by Fourier transform infrared spectroscopy (ATR-FTIR). The self-cleaning property with coal powder was investigated. Corrosion behavior was evaluated using Tafel polarization test and salt fog. The results of the water contact angle showed that the surface roughness due to anodizing and chemical etching reduced the contact angle to 15ᵒ and 24ᵒ, and after modifying the surfaces, the contact angle increased to 157ᵒ and 153ᵒ. After modifying the surface of the anodized sample, it has higher corrosion resistance than the etched sample. The final coating is self-cleaning.

Development of materials with the ideal black body absorption spectrum are of great interest. Such materials could improve the efficiency of solar cells, and passive cooling and heat transfer systems as well as the protective and decorative coatings. Fabricating black anodizing coatings is promising for this purpose because they exhibit low light reflection from the surface. Such coatings can be produced through successive anodizing and black coating of aluminum alloys. In this study, the effect of anodizing repetition on the absorption coefficient of the black anodizing coatings on 2024 aluminum alloy was investigated, as model. All the parameters were fixed in the black coloring stage to evaluate the influence of the anodizing steps. After a one-step anodizing, the black coatings showed an absorption coefficient of 0.956 in the visible region and 0.911 in the of 220 to 2200 nm wavelength range, while their absorption coefficient increased after a three-step anodizing up to 0.982 in the visible region and up to 0.966 in the 220 to 2200 nm wavelength range. This indicates that anodizing repetition helps the optical absorption of black anodizing coatings to approach the optical absorption of an ideal black body.

Increasing the thickness of the oxide layer on the surface of the titanium alloy by electrochemical processes such as anodizing, leads to improved corrosion resistance and ultimately increase the lifespan of titanium implants in the human body. Among the parameters affecting the properties of the anodized layer, process voltage is of great importance with respect to kinetic and thermodynamic processes. In this paper, titanium substrate is subjected to anodizing process in sulfuric acid solution by different voltages such as 3, 6, 9 and 21 volts, electrolyte temperature of 60 ° C and duration of 30 seconds. Then the fuzzy, structural and morphological behavior, as well as the corrosion behavior of the coating are evaluated by GIXRD, FESEM and electrochemical tests such as electrochemical impedance in the simulated body fluid (SBF) solutionat 37 °C, respectively. GIXRD and FESEM analyzes show the formation of a titanium oxide coating with a hexagonal structure, which with increasing voltage up to 6 volts, a smoother and smoother surface was obtained, but further increase of voltage up to 9 and 21 volts, resulted in a rougher surface. Also, the results of corrosion behavior showed that increasing the anodizing voltage up to 6 volts due to the presence of a more uniform and smoother surface, which indicates less surface imperfections, led to the highest load transfer resistance in 1 and 24 hours of immersion in SBF solution at 37354 And 58127 (Ω .Cm2 ) compared to other anodized samples.

For decades, aluminum alloys have been known as one the most vital materials utilized in diverse fields of industry. In spite of significance, Al alloys can be easily exposed to corrosion. In this study, it has been tried to investigate anodic oxide coating made by hard anodizing of 5083 aluminum alloy in sulfuric acid at the temperature of 0 ºC and different voltages (20, 27 and 35 V). Subsequently, all samples were characterized using X- Ray Diffraction (XRD), Scanning Electron Microscope (SEM) and Field Emission Scanning Electron Microscope (FESEM). Low angle XRD results showed that the amorphous alumina coatings were formed in the surface of the samples. SEM images showed that the coatings are porous which is directly related and affected by anodizing voltage. FESEM images of fracture surfaces were indicant of formation and growth of oxide nano-cells in the cross section of the coatings. In order to investigate the properties of the coatings, micro-hardness, roughness and thickness measurement was carried out. Results showed that micro-hardness, roughness and thickness of the coatings increase by increasing the anodizing voltage. Furthermore, potentio dynamic polarization and electrochemical impedance spectroscopy (EIS) tests were performed. Electrochemical analysis proved that by increasing the anodizing voltage, corrosion resistance of the samples declined due to increasing the porosities on the surface of the coatings.

In order to improve the surface properties and the greater use of aluminum and its alloys in various industries, especially aerospace, different coating methods have been introduced. Anodizing and electroless plating are the most widely used methods for this purpose. In this research, the effect of temperature and voltage of anodizing on the surface properties of anodic aluminum oxid (AAO), producred on 2024 aluminum, was investigated. The results showed that with increasing voltage and decreasing temperature, the thickness and roughness of coatings increased. An optimal voltage (45 V) was obtained to achieve the highest hardness at all temperatures. The study of the thickness and hardness of the optimum sample also showed an increase in these two parameters with increasing time. FESEM studies also revealed that by carefully controlling on the anodizing conditions, a structure with regular nano-cells could be obtained. The two step anodizing significantly increased the order of the oxide layer cells. SEM, EDS, and XRD results indicated that the possibility of Ni-P electroless coating applying on anodized aluminum in SLOTONIP 70A solution is well established. To investigate and compare the corrosion behavior of AAO and AAO/Ni-P coatings with aluminum substrate, the polarization method and tafel extrapolation was used. The results indicated that the high corrosion resistance of 2024 aluminum alloy was achieved in the presence of Ni-P electroless coating on anodized alloy. The heat treatment of the samples at different temperatures showed that the highest hardness of the final coating (1185 vickers) would be achieved at 400 °C, and the heat treatment time at this temperature after 75 minutes would not have much effect on the hardness.

The purpose of the present work is to provide a suitable substrate for the deposition of titanium dioxide as a photocatalyst on aluminum. Due to the weak adhesion of photocatalysts to aluminum, there is no possibility of adhering photocatalysts to its surface or the lifetime is very short. For this reason, in this study, the adhesion between TiO2 and aluminum substrate is enhanced by the creation of micron pores on the substrate surface using two methods of anodizing and Plasma Electrolytic Oxidation (PEO) and the results of the two methods are compared. Experiments were carried out to investigate the dye removal over time using Rhodamine 6G aqueous solution in the presence of UV light. SEM images were also prepared from the surface of TiO2-coated aluminum substrates. The results of the study showed that the density of pores on the aluminum surface, and consequently, the dye removal in the PEO method were higher than those of conventional anodizing. In addition, although the dye removal in the PEO method is increased compared to the anodizing method, the overall process time and energy consumption in this method, especially in the pulse mode, were less than those of the anodizing method.

In this paper, the effects of anodizing, solution heat-treatment and hot-rolling on microstructure and corrosion behavior of a biocompatible magnesium alloy containing Zn, Ca, and rare earth elements (REEs) were investigated. The anodizing process using HAE method in 3 various current densities and 2 different times was performed on each of the specimens. The corrosion resistance of samples was evaluated by immersion test in PBS solution at 37 ° C. The resulting oxide film were studied by scanning electron microscopy and the weight loss of the specimens was measured after eliminating the oxide residues. The results showed that a uniform structure with increased grain size is made by solution heat-treatment. This treatment had a favorable effect on the corrosion resistance of the alloy and reduced the corrosion rate by 20%. The hotrolling process likewise increased grain size and reduced the corrosion rate by 9%. Also, the anodizing process generally had a favorable effect on the corrosion properties of the specimens and in the best condition, caused 80% reduction in the corrosion rate. The effect of time and applied current density of the anodizing process was also studied. Results showed different effects for each of samples.

Nowdays, AAO (Anodic Aluminium Oxide) films obtained by anodizing, have vast  applications in different fields of nano. In this study, AAO films production by mild and hard anodizing of 1100 aluminium alloy was investigated in three different conditions, and the characteristic parameters of these films were studied. Results showed that AAO films produced in oxalic acid and sulfuric acid mixture as an anodizing electrolyte needs to lower voltage compared with films produced in oxalic acid electrolyte alone. Mixture of oxalic acid and sulfuric acid generated AAO films with smaller interpore distance and pore diamaeter without any reduction in oxide film quality. Thickness of the barrier layer which is an important parameter for the growth of materials, was also reduced from 155 nm to about 110 nm. Phase analysis results using XRD patterns showed amorphous-crystalline structure of AAO films. EDS results showed the presence of sulfur in these films with addition of sulfuric acid to the anodizing electrolyte, and the more sulfuric acid was added to the solution, the amount of sulfur was increased. This shows high acidic potential of sulfuric acid and its peneteration into the film during anodizing process.

Abstract The aim of this work is to optimize the hardness of anodizing aluminum coating by design of experimental method. Various parameters affect the hardness of these coatings among which time, temperature and pulse current parameters (current density limit, frequency and duty cycle) were considered. According to this, mentioned parameters in different levels were considered as input variables. Also, the effect of parameters on the hardness of anodizing aluminum coating was obtained as a mathematical model. The final model was achieved by Analysis of variance which was used for attaining the best method to predict the maximum hardness of these coatings. The most effective variables and optimized hardness of anodizing aluminum coating were obtained by using the mathematical model. Experimental results showed that temperature and quadratic behavior of duty cycle were the most important terms on the hardness of these coatings. Furthermore, the maximum hardness of this coating was 491Hv, which was attained at the maximum and minimum current densities of 4.09, 1.23 A/dm2, frequency of 146.94 Hz, time of 29.50 min, duty cycle of 65.16% and the bath temperature of 3.13oC.

In this research, ordered porous anodic templates with 30 nm diameter and 15 µm thickness were prepared by using double anodization process. Dip coating method was employed to synthesize strontium ferrite in the form of nanowires in sol dilution. Ferrite nanopowders were also synthesized using sol gel method. The characterization of the nanostructures were examined by X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM) and Energy Dispersive Spectroscopy (EDS). Hysteresis loops of nanopowders and nanowires, parallel and perpendicular to the wires axes, were measured by Superconducting Quantom Interference Device (SQUID). The results showed that double anodization in 0.3 M oxalic acid at 4 oC with a single anodization for 12 hours could produce ordered template. Dip coating in 80 oC for two hours could form fine and uniform strontium ferrite nanowires. The produced material showed parallel anisotropy.