The purpose of this work was to evaluate the effect of three commercial mouthwashes on the corrosion resistance of Ti-10Mo experimental alloy. Experiments were made at 37.0 +/- 0.5 degrees C in a conventional three-compartment double wall glass cell containing commercial mouthwashes. Three mouthwashes with different active ingredients were tested: (I) 0.05% sodium fluoride + 0.03% triclosan; (II) 0.5 g/l cetylpyridinium chloride + 0.05% sodium fluoride; (III) 0.12% chlorohexidine digluconate. The assessment of the individual effect of active ingredients was studied by using 0.05% sodium fluoride. Commercially pure titanium (CP Ti) was used as control. Microstructures from Ti-10Mo experimental alloy and CP Ti were also evaluated using optical microscopy. Ti-10Mo as-cast alloy shows the typical rapidly cooled dendrites microstructure (beta phase) while CP Ti has exhibited a metastable martensitic microstructure. Electrochemical behavior of dental materials here studied was more affected by mouthwash type than by Ti alloy composition or microstructure. In both alloys passivation phenomenon was observed. This process may be mainly related to Ti oxides or other Ti species present in spontaneously formed film. Small differences in passive current densities values may be connected with changes in film porosity and thickness. Protective characteristics of this passive film are lower in 0.05% sodium fluoride + 0.03% triclosan mouthwash than in the other two mouthwashes tested.
Zinc alloys coatings formed with elements of group VIIIB are promising because they display similar properties and protect steel by galvanic action. The Zn-Ni alloy is remarkable by showing improved mechanical properties and better corrosion resistance when compared to zinc coatings of similar thickness, also can be applied at higher temperatures. In this work, electrodeposits of Zn, Zn-12%Ni, obtained upon SAE 1010 steel from commercial alkali baths, were treated by blue chromatization and characterized according to mechanical properties and morphology. Studies were carried out by using measures of hardness, roughness, SEM, EDS and XRD. Among the studied electrodeposits, alloys treated by chromatization showed higher corrosion resistance and Zn-Ni electrodeposits showed higher value of roughness and hardness, while zinc coating had results similar to the steel substrate By means of XRD, it was found that electrodeposits are crystalline, being identified in Zn-Ni alloy the presence of the phases (Ni 5 Zn 21) and (Ni 3 Zn 22), which are responsible for its higher corrosion resistance.
At present, titanium and its alloys stand out for their mechanical and biological properties. Vickers hardness and the effect of 15%, 22% and 35% hydrogen peroxide (H2O2) on Ti-10Mo alloy corrosion were evaluated. A conventional double-walled glass cell was used for thermostatization. As reference electrode was used the Ag/AgCl (s)/KClsat and as auxiliary electrode graphite stick. The work electrodes consisted of Ti-10Mo cylinders embedded in polyethylene, with electrical contact by brass wire and silver paint on one end. The electrolyte used was H2O2 in concentrations of 15%, 22% and 35% and potentiodynamic measurements were recorded. The Vickers hardness was evaluated before the treatment using Vickers penetrator under load of 1000g and dwell time of 10s / measurement separately. The results showed an increase in the corrosion values in direct relation with the increase of the H2O2 concentration. At 35% concentration, at constant current of ~ 1.0V the alloy did not passivate, characterizing high corrosion rate. At the concentrations of 15% and 22% the results showed a tendency to pseudopassivation, with release of TiO2 and part of the product of the corrosion becoming semi-adherent to the surface of the working electrode and another part passing through the middle, characterizing intermediate corrosion velocity. It was concluded that higher H2O2concentrations produced higher electrochemical corrosion.Descriptors: Titanium; Alloys; Surface Properties; Corrosion; Tooth Bleaching Agents.
From industrialized baths, free of cyanide, the corrosion behavior of electrodeposits of zinc and zinc alloys was studied by means of electrochemical tests in aerated solution of 3.5% (0.6 M) NaCl at pH 8.2. In literature, several studies are found about zinc coatings and zinc alloys, for example, Zn-Ni and Zn-Co, nevertheless there is little about the ternary alloy Zn-Fe-Co. The Fe presence in the alloy results in a good adhesion to the substrate and allows application of these materials at higher temperatures. The electrochemical tests were carried out by obtaining open circuit potential curves with immersion time, potentiodynamic polarization curves and cyclic voltammetry. From the obtained results, the large potential differences observed between the steel and the electrodeposits showed that the last protect the substrate, acting as a sacrifice metal. The tests disclosed similar behaviors in both the current densities and the corrosion potential for electrodeposits of Zn and Zn-Fe-Co. After chromate passivation process, a significant decrease in corrosion density was noted for Zn and when the system was de-aerated there was change in the cathodic process mechanism
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