COMPARISON OF TWO STAINING METHODS FOR ANODIZING IN ALLOY 6063 ALUMINUM PROFILES

Background: Aluminum stands out for being a light, corrosion-resistant, and recyclable metal, achieving wide coverage in the market. When incorporated into alloying elements, it is possible to acquire other desirable characteristics. Alloy 6063, intended for architectural purposes, has aesthetic, structural, and strength functions. Anodized finishing is performed through an electrolytic process, ensuring a more resistant aluminum oxide film than that formed naturally. For decorative purposes, the anodic film coloration can be performed by several methodologies, in this case, for the coloration by organic adsorption, with the use of aniline, and the electrolytic coloration, composed of tin sulfate salts, both for obtaining the black color. Aim: Compare of two different staining methods on the surface of anodized profiles of aluminum alloy 6063. Methods: Profile samples were collected and tests were carried out to measure the thickness of the anodic layer, immersion tests with 3,5 percent sodium chloride, for 1000 hours, and neutral saline mist, for 600 hours. Results and Discussion: Both methodologies proved to be resistant to immersion tests with sodium chloride, as well as with neutral saline mist, and these tests are quite aggressive and provide corrosion of the material when not well treated. Corrosion points were only seen at the intersections performed, and in the rest of thearea, no points were detected. Conclusions: The result of both methodologies was positive, considering tht there was no corrosion in the tested samples, except in the intersections performed, as well as the maintenance of the color in both tested methodologies, which was not expected in the literature. For future work, it is suggested to deepen the study to perform electrochemical impedance spectroscopy tests for exaluate the strength of the anodic film and perform anodizing with the same parameters, however, with different anilines to analyze their behavior.

Improved Corrosion Resistance of Magnesium Alloy AZ31 in Ringer Lactate by Bilayer Anodic Film/Beeswax–Colophony

A bilayer anodic film/beeswax–colophony is proposed for improving the corrosion resistance of magnesium alloy surface. The bilayer was synthesized on the AZ31 alloy by anodization and subsequent dip coating, and the corrosion behavior was investigated by electrochemical measurements and weight loss test in Ringer lactate at 37 °C. The bilayer improved the electrochemical corrosion resistance by four orders of magnitude, as demonstrated by ~104 times lower corrosion current density in the polarization curves and ~104 higher film resistance in the impedance spectra. The tremendous surface area of the porous anodic film led to a strong attachment of the topcoat beeswax–colophony. Most of the coating remained attached to the surface after 14 days soaking in Ringer lactate. A few small blisters developed under the bilayer contributed to the low mass loss of 0.07 mg/cm2/day compared to the bare substrate, with an average loss rate of 0.25 mg/cm2/day. Local detachment of topcoat layer exposed the underlying anodic film that triggered the deposition of Ca and further nucleation of the Ca–P compound on the surface. The existence of a Ca−P compound with a Ca/P ratio of 1.68 indicated the ability of the bilayer to promote the formation of bone mineral apatite.

Mechanism of action of tin on the semi-conductive properties of PbO layer in lead acid battery

Although antimony in alloys for lead-acid batteries has better mechanical and electrochemical performance, it reduces the excessive potential for hydrogen evolution, resulting in excessive water loss and self-discharge of the battery. This paper aims to examine the action of tin in PbSn using different techniques. In this work, the addition of tin in PbCa was intended to suppress the premature capacity loss (PCL) caused by the substitution of antimony in the PbSb alloy by calcium that has good mechanical properties and a high hydrogen evolution potential (200 mV higher than that of antimony). This substitution induces the formation of a passive film composed mainly of α-PbO. The mechanism of action of tin on the anodic film obtained at 700 mV vs. Hg/Hg2SO4/K2SO4 saturated electrode with Pb – (0–5) wt.% Sn in 0.5 mol/L sulfuric acid solution at 25 °C was studied using electrochemical impedance spectroscopy (EIS), AC voltammetry, Mott–Schottky plots and X-ray diffraction (XRD) of the film obtained. It was found that tin stops the growth of the anodic film due to the co-precipitation of certain conductive oxides which reduce the thickness of the passive film and increase its conductivity. A mechanism of action of tin on the electrochemical behavior of the anodic film was suggested based on the results.

Influence of Electrolyte Temperature on Morphology and Properties of Composite Anodic Film on Titanium Alloy Ti-10V-2Fe-3Al

In this study, we introduced a novel environmentally-friendly electrolyte consisting of polytetrafluoroethylene (PTFE) nanoparticles and malic acid solution to fabricate composite anodic film on Ti-10V-2Fe-3Al alloy at different electrolyte temperatures. The morphology revealed that the PTFE nanoparticles were successfully incorporated into composite anodic films and embedded preferentially in the pores and cracks. Their performances (wear, corrosion and hydrophobicity) were evaluated via electrochemical tests, ball on disc tests, and a contact angle (CA) meter. Compared to the substrate of titanium alloy Ti-10V-2Fe-3Al, the composite anodic films exhibited the low wear rates, high corrosion resistance and good hydrophobicity. However, the microstructure and morphology of the films were affected by the electrolyte temperature. As a result, their performances were changed greatly as a function of the temperature and the film fabricated at 20 °C exhibited better performances (CA = 131.95, icorr = 6.75 × 10−8 A·cm−2, friction coefficient = 0.14) than those at other electrolyte temperatures. In addition, the corresponding lubrication mechanism of the composite anodic films was discussed.