A study of the electrochemical reactivity of titanium under cathodic polarization by means of combined feedback and redox competition modes of scanning electrochemical microscopy

Sensors and Actuators B. Chemical, 320 (2020) 128339. https://doi.org/10.1016/j.snb.2020.128339.The effect of cathodic polarization on the electrochemical behavior of the thin titanium dioxide film formed by anodic pretreatment over pure commercial titanium metal for biomaterial application was investigated in situ using scanning electrochemical microscopy (SECM). Quantitative information on the electron transfer rates (keff) at the titanium surface was obtained using the feedback operation of SECM using ferrocene-methanol (FcMeOH) as electrochemical mediator. An increase of keff values with the increase of the negative polarization was detected, a feature that correlates well with the decrease of titanium oxide resistance with increasing cathodic polarization observed using electrochemical impedance spectroscopy (EIS). In addition, SECM operation in the redox competition mode proved that hydrogen was absorbed in the surface oxide film leading to changes in conductivity and electrochemical reactivit

A scanning electrochemical microscopy characterization of the localized corrosion reactions occurring on nitinol in saline solution after anodic polarization

Sensors and Actuators B: Chemical 321 (2020) 128610. https://doi.org/10.1016/j.snb.2020.12861

In situ investigation of the cytotoxic and interfacial characteristics of titanium when galvanically coupled with magnesium using scanning electrochemical microscopy

Recently, the cytotoxic properties of galvanically coupled Mg-Ti particles have been shown to different cells, although this cytotoxic effect has been attributed mainly to Mg due to its tendency to undergo activation when coupled with Ti forming a galvanic cell consisting of an anode (Mg) and a cathode (Ti). However, the role of the Ti cathode has been ignored in explaining the cytotoxic effect of Mg-Ti particles due to its high resistance to corrosion. In this work, the role of titanium (Ti) in the cytotoxic mechanism of galvanically coupled Mg-Ti particles was examined. A model galvanic cell was prepared to simulate the Mg-Ti particles. The electrochemical reactivity of the Ti sample and the pH change above it due to galvanic coupling with Mg were investigated using scanning electrochemical microscopy (SECM). It was observed that the Ti surface changed from passive to electrochemically active when coupled with Mg. Furthermore, after only 15 min galvanic coupling with Mg, the pH in the electrolyte volume adjacent to the Ti surface increased to an alkaline pH value. The effects of the galvanic coupling of Ti and Mg, as well as of the alkaline pH environment, on the viability of Hs27 fibroblast cells were investigated. It was shown that the viability of Hs27 cells significantly diminished when Mg and Ti were galvanically coupled compared to when the two metals were electrically disconnected. Next, the generation of reactive oxygen species (ROS) increased when the Ti and Mg were galvanically coupled. Thus, although Ti usually exhibited high corrosion resistance when exposed to physiological environments, an electrochemically active surface was observed when galvanically coupled with Mg, and this surface may participate in electron transfer reactions with chemical species in the neighboring environment; this participation resulted in the increased pH values above its surface and enhanced generation of ROS. These features contributed to the development of cytotoxic effects by galvanically coupled Mg-Ti particles

Microelectrochemical characterization of titanium biomaterials by scanning electrochemical microscopy

8Aims of the workTitanium and its alloys are of great industrial interest due to their versatility. They have broad-scale applications especially in aeronautics, electrochemical industries, and orthodontia. Indeed, the titanium alloys have been widely used for clinical applications such as dental implants, stents, and orthopedic devices because of their biocompatibility and their outstanding mechanical properties such as low elastic modulus, high tensile strength, and low density. Also, they are known for their exceptional osseointegration character functioning in living tissue. Besides, they are well known for the formation of robust protective film on the surface. That provides a high corrosion resistance via inhibiting the release of metal cations from the surface and hinders the electron transfer reactions with the surrounding environment. However, the clinical problems of titanium and its alloys were broadly reported. Metal ions were detected in blood and urine also localized corrosion was observed in vitro and in vivo. In fact, the improvement of properties of titanium-basedbiomaterials required a deep comprehension of the electrochemical featurethat take place on their surface.The corrosion resistance of frequently used biomaterials made of pure titanium, and its alloys such as Nitinol, as well as its change upon different mechanical and physiological impacts is an extremely important character. Most of the corrosion studies of objects used as implanted medical supports were done with conventional methods. The reports appeared about the results of these experiments however, turned up some questions, or uncertainties. Application measurements with new ultramicroelectrodes combined with the conventional methods seemed very promising for obtaining fine details about the corrosion resistance and about its changes. It was specially so far using SECM with its different modes and measuring micro tips. In my research I planned to prepare different ultramicroelectrodes applicable in SECM measurement, work out selective SECM methods applicable for corrosion studies and use them in examination of the corrosion of biomaterial objects made of titanium and titanium alloys

Do titanium biomaterials get immediately and entirely repassivated? A perspective

Abstract Titanium and its alloys have been widely used for clinical applications because of their biocompatibility and exceptional chemical inertness, in addition to their outstanding osseointegration characteristics. They are well known to form a robust protective film on the surface that provides a high corrosion resistance with the surrounding environment. Although this passive state of titanium-based materials is often considered to be achieved very rapidly, even when damaged, and to be chemically stable in physiological environments, evidences of passivity breakdown and electron transfer reactions have been collected using high resolution microelectrochemical techniques. Thus, further optimizations are required for their forthcoming applications