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

The behavior of titanium ahoy grade 7 under the influence of micro-organism s in diluted NaBr solution was studied. The exposure of the tested titanium alloy to aqueous environments combined with micro-organisms was carried ou t in a unique test cell under induced potential. During the exposure, the p otential between the anodic surface and the reference electrode was recorde d. A heavily polluted environment with micro-organisms resulted in a sharp drop of the steady potential after an incubation period of approximate to 2 -4 h. Potentiodynamic polarization measurements show that increasing the to tal bacterial counts (TBC) to a value > 10(4)/ml results in higher sensitiv ity to localized corrosion attack. As the TBC increases, the anodic breakdo wn potential decreases from approximate to 950 mV in 10(2)/ml to approximat e to 800 mV in 10(7)/ml. The results clearly indicate that the aqueous medi a polluted with micro-organisms inhibits the anodic passivation process and depolarizes the cathodic process, resulting in higher corrosion current de nsity. SEM observation of Ti 7 ahoy that was exposed to heavily polluted en vironments with micro-organisms for approximate to 3 months revealed a mass ive growth of biofilm on the metal surface. (C) 2001 Elsevier Science B.V. All rights reserved.