Now, the use of any medical device based on metals or alloys, especially intended for dentistry applications, is impossible without preclinical evaluation of its anticorrosion properties. Today, the use of stainless steels with AISI standardization, with predilection 316L and 321, are preferred for ergonomic reasons due to their high operational reliability and optimal mechanical properties for functionality over time. In this regard, 316L and 321 stainless steels are tested for comparison in the solution that simulates human saliva with different pH. Stainless steel samples were subjected to corrosion in Fusayama-Meyer and Carter-Brugirard saliva. In-situ electrochemical measurements were applied, such as the open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS). The results show that the corrosion resistance of 316L is superior to 321 in saliva solution at both pH values.

In this paper there are presented some results obtained by open circuit potential and electrochemical impedance spectroscopy measurements from studies performed on the behavior of tribocorrosion on metallic implant biomaterials as: 304L stainless steel, Co/nano-CeO2 nanocomposite layer and Ti6Al4V untreated and oxidized alloy to form a nanoporous TiO2 film. The open circuit potential technique used in measuring the tribocorrosion process provide information on the active or passive behavior of the investigated metallic biomaterial in the biological fluid, before, during friction and after stopping the friction. Thus it clearly show a better behavior of Co/nano-CeO2 nanocomposite coatings as compared with 304L stainless steel to tribocorrosion degradation in Hank solution; as well the better behavior of nanoporous TiO2 film formed annodically on Ti6Al4V alloy surface as compared with untreated alloy to tribocorrosion degradation in artificial saliva Fusayama Meyer. The slight decrease in polarization resistance value resulted from electrochemical impedance spectroscopy measured during friction in the case of the Co/nano-CeO2 nanocomposite layer (four times smaller), compared to 304L stainless steel, whose polarization resistance decreased more than 1000 times during friction shows the higher sensitivity of stainless steel to degradation by tribocorrosion. The same behavior is observed when comparing the polarization resistance of untreated titanium alloy recorded during friction that is about 200 hundred times smaller, while the specific polarization resistance of the oxidized alloy with the nanoporous film of titanium oxide, decreases very little during friction, highlighting the beneficial effect of modifying the titanium alloy by anodic oxidation to increase its resistance to the degradation process by tribocorrosion.

The aim of this paper was to study the corrosion behavior of Nickel – Base – Dental Alloys in Ringer biological fluid. The Nickel base alloys are widely used for medical purposes, especially for prosthetic works in the field of dentistry. The applied electrochemical methods used for corrosion investigations are Open Circuit Potential, Linear Polarization during time of immersion in order to calculate the polarization resistance and corrosion rate. Potentiodynamic Polarization diagrams was performed to appreciate the passive domain. Ni-Cr Ugirex alloy show a better corrosion resistance in Ringer solution which will be reflected in a longer life of the dental structures made with this alloy as compared to the Ni-Cr Ducinox alloy, which will result in dental structures with a shorter lifespan.
The electrochemical studies has shown that the alloy have a corrosion behavior similar to a passivating alloy, displaying an extensive passivity area due to formation of an oxide film.

This paper deals with the effect of impeller shape on off-bottom particle suspension. On the basis of numerous suspension measurements, correlations are proposed for calculating the just-suspended impeller speed for a standard pitched four-blade turbine and three types of hydrofoil impellers produced by TECHMIX for several particle sizes and for a wide range of particle concentrations. The suspension efficiency of the tested impellers is compared with the efficiency of a standard pitched blade turbine on the basis of the power consumption required for off-bottom suspension of solid particles. It is shown that the standard pitched blade turbine needs highest power consumption, i.e. it exhibits less efficiency for particle suspension than hydrofoil impellers produced by TECHMIX.