Evaluation of Corrosion Resistance of Implant-use Ti6Al4V Alloy in Hank Biological Solution in the Presence of Microorganism's Metabolic Product Lactic Acid

Titanium alloys such as Ti6Al4V is the most used alloy used as implant for biomedical purposes. The conditions for a biomaterial to be selected for a particular application in the human body is that this should to conforms to the physical, chemical and biological characteristics, more precisely to be biocompatible, biofunctional and not ultimately sterilizable. Ti6Al4V alloy has mechanical properties suitable for many biomedical applications and has excellent corrosion resistance, which depends on the presence of a stable passive oxide film forming on its surface. Our study aims to evaluate the corrosion resistance of Ti6Al4V as a function in time with addition of 5 g/L and 10 g/L Lactic acid in biological solution Hank after exposure at 0 h (at immersion time), after 48 h (from immersion) and 168 h (from immersion). The evaluation of corrosion resistance of Ti6Al4V in Hank biological solution with addition of two concentration of Lactic acid it was done by electrochemical methods in terms of open circuit potential and polarization resistance (Rp). Lactic acid is used in this study because it is a component present in human blood in small quantities and is necessary for the metabolic processes used directly by the heart muscle, brain and nervous system. The increased lactic acid content in muscle appears as weight-bearing exercises. This is why it is important to know how the presence of lactic acid in larger quantities affects the implants. The study also highlights the importance of using longer testing times and more realistic solutions when testing biomedical materials

Study of Tribocorrosion Processes by Electrochemical Techniques

Tribocorrosion is defined as the chemical-electrochemical-mechanical process leading to a degradation of materials in sliding, rolling or erosion contacts immersed in a corrosive environment. That degradation results from the combined action of corrosion and wear. The mechanism of tribocorrosion is not yet fully understood due to the complexity of the chemical, electrochemical, physical, and mechanical processes involved. Examples of the occurrence of tribocorrosion in service are the accelerated corrosion of steel conveyors exposed to ambient air of high relative humidity, the fall out of electrical connectors in the automotive industry, the degradation of hip prosthesis and dental fillers, the erosion wear of turbine blades, etc. The combined corrosion-wear degradation of materials in sliding contacts immersed in electrically conductive solutions is investigated in-situ by electrochemical techniques. Such techniques are the open circuit potential measurements, EOC, the potentiodynamic polarization measurements, PD and the electrochemical impedance. Capabilities and present limitations of these techniques are discussed based on a tribocorrosion study of a cobalt chromium alloy hard coating (Stellite6) and stainless steel (304L) immersed in water-based electrolytes, namely aerated 0.5 M sulphuric acid, Ringer solution or cooling water reactor (12 ppm Li as LiOH+1000 ppm Boric Acid) and sliding against a corundum counterbody. Some novel insights into the tribocorrosion mechanism of active and passive materials are discussed. These in-situ electrochemical data provide insights into a possible synergism between corrosion and wear processes in sliding contacts. This paper concludes on the benefit of using different electrochemical analyzing techniques when investigating the behaviour of materials under corrosion-wear test conditions

Comparative Corrosion Behavior of Pure Copper and Brass in 3.5% NaCl Solution

Copper and brass are used in many economic sectors as electrical, construction, transport and others. From common household electrical wiring to boat propellers and from photovoltaic cells to saxophones, copper and its alloys are employed in a variety of end-uses. Copper tubing is now the standard material for potable water and heating systems in most developed countries. This is in part due to its bacteriostatic properties, or in other words due to the ability of copper to inhibit the growth of bacterial and viral organisms in water. Therefore, the corrosion resistance of copper and brass are important in defining the field of use as construction parts. This paper aims at investigating the comparative corrosion behavior of pure copper and brass in 3.5 % NaCl solution. The corrosion behavior of both type samples in 3.5% NaCl solution was investigated by the use of electrochemical methods as open circuit potential and linear polarization resistance measurements. The results show an improved corrosion resistance of pure copper sample in 3.5 wt. % NaCl solution as compared with brass sample

The Effect of Fluoride Containing Toothpaste on the Electrochemical Behavior of 316L Stainless Steel for Dentistry Applications in the Human Saliva

The study aims to investigate the effect of fluorinated toothpaste added in Fusayama-Meyer saliva in order to evaluate the electrochemical behavior of 316LSS for dentistry applications. For electrochemical behavior in situ electrochemical measurements such as: Open circuit potential (OCP), Linear Polarization (PL), Potentiodynamic Polarization (PD) and Electrochemical Impedance Spectroscopy (EIS) were applied. The results show a comparative analysis of the electrochemical behavior and corrosion resistance of 316L-SS in human saliva containing high fluoride toothpaste for dentistry applications. From the electrochemical results it can be concluded that the addition of fluoride toothpaste in Fusayama-Meyer saliva decreases the corrosion resistance of 316L-SS and therefore will reduce the lifetime of dentistry structures or devices

Tribocorrosion – Insight into Material Degradation in Specific Environments

Tribocorrosion is an irreversible surface degradation mechanism of a metallic and/or non-metallic material as a result of its physicochemical and mechanical interactions during relative motion (friction, sliding, impact, abrasion, erosion) in corrosive media. It encompasses synergistic effects between mechanical wear and chemical / electrochemical processes which interact with each other. Tribocorrosion processes lead to uneconomical material loss as well as to the decreasing of the following characteristics: durability, reliability, safety, performance, energy efficiency, pollution and health. Recent activity in tribocorrosion research aims at addressing the need to select or design new surfaces for future equipment as well as minimizing the operating costs and extending the life of existing machinery and medical devices. The work presents an overview and some experimental results from tribocorrosion tests of biomaterials and nanocomposite coatings in specific environments from physiological solutions to industrial environments

Nanocomposite Coatings Obtained by Electro-Co-Deposition of Inert Particles with Cobalt–a Review

The paper focuses on review investigations of electrodeposition processes of metallic coatings containing dispersed nanosized particles. The nanosized particles, suspended in the electrolyte by agitation and/or use of surfactants, can be electroco-deposited with the metal. The inclusion of nanosized particles can give (i) increased microhardness and corrosion resistance, (ii) modified growth to form a nanocrystalline metal deposit and (iii) a shift in the reduction potential of a metal ion. Many operating parameters influence the quantity of incorporated particles, including current density, bath agitation (or movement of work piece) and electrolyte composition. High incorporation rates of the dispersed particles have been achieved using (i) a high nanoparticle concentration in the electrolyte solution, (ii) smaller sized nanoparticles; (iii) a low concentration of electroactive species, (iv) ultrasonication during deposition and (v) pulsed current techniques. Compositional gradient coatings are possible having a controlled distribution of particles in the metal deposit and the theoretical models used to describe the phenomenon of particle co-deposition within a metal deposit are critically considered

Sulphate Reducing Bacteria in Biofilms on Thermosetting Polymers/Zn Composite Layers

Bacterial adhesion to surfaces is the first step in the formation of a biofilm and has been studied extensively over the past decades in many diverse applications. Sulphate Reducing Bacteria (SRB) is a group of phylogenetically diverse anaerobic microorganisms that were first discovered by Beijerinck in 1895. This work investigates the attachment of Sulphate Reducing Bacteria and the modification of roughness before and after the attachments on the surfaces of zinc and thermosetting polymers/zinc composite layers obtained by electro co-deposition. There were used two types of thermosetting polymers: phenol – formaldehyde resin (type NOVOLAC) and epoxi resin. For investigations of the surfaces were used atomic force and epifluorescence microscopy methods (AFM and EFM, respectively). Sessile bacteria on coupons were stained with 4’, 6-diamidino-2-phenylindol (DAPI) and visualized by EFM as well as AFM. The best imaging conditions for AFM were assessed

Surface Roughness and Topography of Ni / Micro-SiC Layers: Influence of Current Density on Electrodeposition Process

The surface properties are directly responsible for the performance of engineering materials because most of failures such as friction, wear, corrosion and fatigue often take place on the material surface. Electrodeposition technique is of great interest for industrial usage because it produces functional and protective coatings with low cost and easy control. The present work has the purpose to evaluate roughness and to analyze surfaces of Ni / micro-SiC composite layers obtained at different parameters for electrodeposition. The layers were electroplated from a Watts bath with a suspension of SiC particles (mean diameter size of particles 30 μm) by adding 5 g/L of particles. Electrodeposition took place at 40 oC and a current density of 2 A/dm2 and 4 A/dm2 for 1h. The suspension bath was stirred by a mechanical stirrer at a constant rotational speed of about 500 rpm. The roughness and topography of the layers were evaluated by atomic force microscopy (AFM) method

Electrochemical Modifications of Titanium and Titanium Alloys Surface for Biomedical Applications – a Review

The field of biomaterials requires the input of knowledge from very different areas such as biology, medicine and engineering so that the implanted material in a living body to not induce any adverse impacts. The paper focuses its attention mainly on titanium and titanium alloys, even though there are biomaterials manufactured from other metals, ceramics, polymers and composite materials. Both electrodeposition and anodic oxidation surface modification methods are discussed with several examples and a brief description of underlying theory, in order to improve the mechanical, chemical and biological properties of these materials

Effect of Mean Diameter Size of Disperse Phase on Morphology and Corrosion Resistance of Phenol – Formaldehyde Resin/Zn Coatings

The present work has the purpose of obtaining composite coatings using phenol – formaldehyde (PF) resin electrodeposited with zinc. The phenol – formaldehyde resin/Zn coatings were electrodeposited from a suspension of PF resin particles with two dimensions for mean diameter size of particles (0.1-5.0 μm and 6-10 μm) in aqueous zinc sulphate electrolyte. Suspension was prepared by adding 10 g/L PF resin particles into solution. The thickness and morphology of the coatings were investigated by SEM method. By adding PF resin in zinc electrolyte for electrodepositing we obtained a very good distribution of PF resin particles on zinc surface. The electrochemical behavior of the layers in the corrosive solution was investigated by electrochemical methods. As electrochemical test solution 0.5 M sodium chloride was used in a three electrode open cell. It was observed that by adding PF resin particles in zinc electrolyte for electrodeposition  were obtained composite layers more resistant to corrosive attack of 0.5 M NaCl than pure zinc obtained from electrodeposition at the same parameters for electrodeposition. Corrosion rate for pure zinc coatings was 72.05 µm/year versus 15.34 µm/year for coatings with mean diameter size of particles 0.1-5.0 μm, respectively 10.11 µm/year for coatings with mean diameter size of particles 6-10μm. Values of polarization resistance obtained with both electrochemical methods (potentiodynamic polarization and electrochemical impedance spectroscopy) were in a very good agreement