Increasing of the corrosion resistance of the Ti6Al4V alloy by high thickness anodic oxidation

Oxide films with different thicknesses and electrochemical properties can be anodically formed on titanium and titanium alloys. In this work the resistance, and particularly, the passivity currents of a Ti6Al4V alloy anodized under different conditions were evaluated. The tests were performed in a physiological solution simulating the environment of the human body. A significant reduction in the passivity current and an increase of the range of passive potentials have been observed on anodized specimens. Consequently the anodic oxidation of the Ti6Al4V alloy to obtain an high thickness oxide film can be considered an important improvement in the finishing of prosthetic devices.     

Cathodic protection and cathodic preventionin concrete: principles and applications

The paper deals with the principles of cathodic protection for atmospherically exposed concrete structures, the various protecting effects induced by the cathodic polarization and tests and field experience results. The differences between the cathodic protection applied for controlling the corrosion rate of chloride contaminated co nstructions and that applied to improve the corrosion resistance of the reinforcement of new structures expected to become contaminated are then underlined and discussed. The more recent applications of cathodic protection on carbonated concrete are also illustrated. The operating conditions (voltage and current applied), the throwing power, the protection conditions which avoid the risk of hydrogen embrittlement in prestressed structures are also discussed. Examples of cathodic protection and of cathodic prevention are also presented.     

CHROMATOGRAPHIC RESOLUTION OF ENANTIOMERS

In the pharmaceutical industry, the increasing demand of new single enantiomer products has raised a great interest towards chromatographic separation methods. While analytical applications of high performance liquid chromatography and gas chromatography are well established, the scaling up to preparative applications still needs a better comprehension and rationalization of the elementary phenomena involved.

In this work the analytical and preparative separation of an isoxazoline racemic mixture on triacetylcellulose has been studied. In order to determine the thermodynamic properties and the equilibrium isotherms of adsorption several experiments at very low concentration (in a HPLC column) and at higher concentrauon (using the frontal analysis technique) have been performed. Moreover, pulse experiments on a preparative column have been run at different temperature and at different racemic concentration. The comparison between experimental data and model results is discussed.     

Characterization of photocatalytic and superhydrophilic properties of mortars containing titanium dioxide

Environmental pollution arising from industrial implants and urban factors is constantly increasing, causing aesthetical and durability concerns to urban structures exposed to the atmosphere. This work is aimed at the study of a system which could take advantage of functionalized building materials in order to improve the quality of urban surfaces, and possibly of the environment itself: TiO₂-containing photoactive materials represent an appealing way to create self-cleaning surfaces, thus limiting maintenance costs, and to promote the degradation of polluting agents. Several mortars containing anatase TiO₂, added as suspension or as powder, were characterized: among the photocatalytic mortars, the use of a combined additive (both powder and suspension) improved the material response. The best photoefficiency was exhibited by a mortar containing TiO₂ as surface covering; nevertheless, the adhesion problems shown by the surface layer open the way for future widening of investigations focused on the optimization of layer durability.     

Hydrodynamic instabilities in electrolytic gas evolution

Both the direct evidence from cine pictures and the analysis of systematic electrochemical investigations support a general explanation of the anode (or cathode) effect, which is based on the conditions of hydrodynamic instability described by Helmholtz and Taylor. Further confirmation of this hydrodynamic interpretation is provided by recent critical current density studies carried out to ultimately establish a method for in situ determination of the alumina content in cryolite-alumina melts.