Electrochemical Characterization of Ti and Ti Base Alloys under Simulated Body Fluid Environment

Abstract

Ti and Ti based alloys are characterised by a continuous electrochemical monitoring and a rapid straining electrode technique in simulated body fluid environment. Materials examined are Ti, Ti-6Al-7Nb, Ti-6Al-4V and Ti-29Nb-13Ta-4.6Zr. Sterilized specimens were immersed in Hanks solution or Eagle’s minimum essential medium (MEM) solution. Electrode potential and polarization resistance were simultaneously and continuously measured up to 7 days. For all the specimens examined, the corrosion potential reached to a steady state in 2 days for both solutions. On the other hand, corrosion resistance increased monotonously for the period examined. Tensile specimens were rapidly elongated under potentio-static polarization to evaluate the transient current after exposure of newly-created surface. The anodic current appeared during both elastic and plastic deformation. For Ti alloys, anodic current started to increase gradually during elastic deformation, then increased more rapidly to reveal a maximum when straining was stopped, then decreased. Pure Ti, on the other hand, revealed the transient current after plastic deformation, but does not show any current increase during elastic deformation. The larger dissolution for a straining was observed as the following order; Ti, Ti-29Nb-13Ta-4.6Zr, Ti-6Al-7Nb, then Ti-6Al-4V.

Passivity Breakdown and Repassivation on TiNi During Rapid Straining Accompanying Martensitic Phase Transformation

“…According to the rapid straining electrode test, passive films are broken during plastic deformation to yield newly created surface. No passivity breakdown, however, occurs during an elastic deformation, that is typically a tensile strain of less than 0.5 % [4]. Therefore, it is interesting to analyze the film breakdown and repassivation behavior on Ti-Ni shape memory alloy under dynamic deformation, because shape memory alloys exhibits very large pseudo-elasticity induced by martensitic deformation, which might result in breakdown of surface oxide films.…”

Breakdown of Passive Films and Repassivation of Ti-6Al-4 V Alloy with Rapid Elongation in Simulated Body Fluid including Osteoblast-like Cells

“…The breakdown of passive films comprises the release of metallic ions which can result in toxic damage to the human body. 13 The breakdown of passive films and subsequent metal dissolution have been examined under deformation of substrate in simulated body fluid. [14][15][16][17][18] Usually, the passive film is repaired by repassivation after breakdown.…”