Titanium alloy grade 7 under the influence of micro-organisms in diluted NaBr solution

The behavior of titanium alloy grade 7 under the influence of micro-organisms in diluted NaBr solution was studied. The exposure of the tested titanium alloy to aqueous environments combined with micro-organisms was carried out in a unique test cell under induced potential. During the exposure, the potential between the anodic surface and the reference electrode was recorded. A heavily polluted environment with micro-organisms resulted in a sharp drop of the steady potential after an incubation period of ≈2–4 h. Potentiodynamic polarization measurements show that increasing the total bacterial counts (TBC) to a value >104/ml results in higher sensitivity to localized corrosion attack. As the TBC increases, the anodic breakdown potential decreases from ≈950 mV in 102/ml to ≈800 mV in 107/ml. The results clearly indicate that the aqueous media polluted with micro-organisms inhibits the anodic passivation process and depolarizes the cathodic process, resulting in higher corrosion current density. SEM observation of Ti 7 alloy that was exposed to heavily polluted environments with micro-organisms for ≈3 months revealed a massive growth of biofilm on the metal surface.