Papers by Keyword: Anodic Film

Abstract: Electrochemical techniques can be used in the various fields, such as anodization, deposition, etching, polishing, pitting, and corrosion applications. In this paper, we focus on the high quality coloring anodic film fabrication. In the prior technologies, anodization generally has the main purpose of surface decoration or corrosion resistance. However, in the high technologies, the characteristics of film thickness, anti-voltage value, surface roughness, surface color and hardness of the anodic film have been strict requirements. The key parameters of anodization such as, electrolyte composition, current-voltage curve pattern, temperature, current density, time, final voltage, efficiency, and electricity affect the quality of anodic film. In order to make a high quality anodic film, this paper provided a detail anodization process and discussed the quality of anodic film.

Abstract: The surface morphologies, chemical composition, phase composition, compactness, thickness and the corrosion resistance of porous anodic films prepared in the sulfuric electrolyte with different additives at 35°C were investigated by XRD, FESEM, EDS, drop method in this paper. The additives are including organic acids, polyhydric alcohols and rare earth (REE) salts. It is indicated that a porously anodic film with about 20 nm holes in diameter can be obtained by additives into the sulfuric electrolyte. The main chemical compositions of the anodic films are Al, O elements, and a small amount of S. The film after boiling water sealing is composed of boehmite phase (Al₂O₃·H₂O) and alumina (Al₂O₃). The corrosion resistance of the anodic film can be improved by the coupling effect of the additives. The mechanism is discussed.

Abstract: The characteristics including surface morphology, phase constitution, thickness and the corrosion resistance of the porously anodic films prepared in the sulfuric electrolyte with different additives at 35°C were investigated by SEM, EDS, XRD and electrochemical polarization method in this paper. The additives are organic acids, polyhydric alcohols and rare earth (REE) salts. A porous anodic film with about 20 nm holes in diameter can be obtained by additives into the sulfuric electrolyte. The main chemical compositions of the anodic films are Al, O elements, and a small amount of S. The film after boiling water sealing is composed of boehmite (Al₂O₃·H₂O) and alumina (Al₂O₃) phases. The compactness and the thickness of the anodic films can be improved by the coupling effect of the additives, which increases the corrosion resistance of the film. The effect of additives on morphologies and corrosion resistance is discussed.

Abstract: Galvanic corrosion behavior of TC4 titanium alloy coupled LY12 aluminum alloy was investigated in 3.5% NaCl solution. Particular attention was given to the effect of three different oxidation films. Galvanic corrosion test was conducted on TC4 titanium alloy which coupled LY12-sulfuric acid anodic film (LY12/A(S)), LY12-chromic acid anodic film (LY12/A(Cr)), LY12-hard anodic film (LY12/A(S) hd) and bare LY12, respectively. Galvanic corrosion current (Ig) and average galvanic current density (Ig’) were monitored. Corrosion morphology was observed by camera and corrosion mechanism was discussed. The results show that the three anodic films improve the corrosion resistance of the anode in different magnitudes. LY12/A(S) hd is found to be least susceptible to galvanic corrosion when coupled TC4 titanium alloy. LY12/A(S) and LY12/A(Cr) are found to be moderately susceptible to galvanic corrosion. But the bare LY12 is highly susceptible to galvanic corrosion in corrosive environment.

Abstract: The effect of different factors on the corrosion performance of the anodic film formed on AZ31 was studied by using electrochemical impedance spectroscopy (EIS) and Tafel polarization curves techniques. The result of EIS showed that the oxide film formed at 20 mA·cm^-2 had the highest corrosion resistance and the optimum temperature was 40°C. The similar conclusion was drawn by the Tafel polarization curves. Moreover, the equivalent electrical circuit R(C(R (QR))) (CR) was used to analyze the EIS data.

Abstract: Lithium ion was introduced into high purity aluminum (99.999%) by hydrotalcite precursor method, and Li/Al composite anodic film was obtained by anodizing. The methods of X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to investigate the properties of the anodic film. The electrochemistry behaviors of composite anodic film were studied by means of potentiodynamic method and electrochemical impedance spectroscopy (EIS). The results showed that the composite anodic film was produced by hydrotalcite precursor method and which is amorphous to X-ray diffraction. The passivation current density of the anodic film in NaCl solution (1mol/L, pH=3, 7, 11) decreased obviously, while impedance value increased sharply. Corrosion resistance of the composite anodic film in NaCl solution was improved by the introduction of Li+ ion.

Abstract: The electrochemical behaviors of anodized and sealed aluminum alloys in NaCl solution were studied by potentiodynamic polarization, the open-circuit-potential and EIS. The results show that anodic oxidization of aluminum increases its corrosion resistance greatly. Different sealing methods have different influences on corrosion behavior of the anodized alloys in NaCl solution; corrosion resistance increases in the order: no sealing < water sealing < dichromate sealing < nickel fluoride sealing. The modulus of the porous film sealed by dichromate solution increases with the immersion time in NaCl solution, which is similar to the self-sealing effect of unsealed anodic films.