Long term in vitro investigation of titanium and some titanium alloys usedfor surgery implants

The paper investigates the long term, "in vitro" corrosion resistance of su rgical implant Ti and two titanium alloys, Ti-6Ai-4V and Ti-5Al-2.5Fe in Ri nger's solution of various pH.'s (2.54; 4.25; 7.53), pointing out the possi bility to appear the local corrosion because of some pH gradients on the di fferent areas of the implant surface. Ti and its alloys are self passivated and the corrosion potentials of the alloys are nobler than base metal (wit h the exception of Ti-5AL-2.5Fe alloy at acid pH, 2.54); the potential Delt a E-cor and current dip gradients, which can appear as a result of the pH c hanges, have the significant values and can determine the intensification o f the corrosion. These surgical implants are used for dong term (20 years) and it is possibly to rake place the hydrolysis of different compounds of t he passive film (like aluminium oxides and vanadium compounds) and therefor e to appear the important pH changes which can generate the potential and c urrent gradients like these simulated in this paper and so it exists the po ssibility of local acceleration of the corrosion on some areas of the impla nt.