Dezincification of aluminum brass by action of Pseudomona fluorescens (ATCC 17552)

MARÍA BEATRIZ VALCARCE; SUSANA R. DE SANCHEZ; MARCELA VAZQUEZ

Lisboa, Portugal

Congreso; EuroCorr2005; 2005

Federacion Europea de la Corrosion

Microbiologically influenced corrosion is a common problem associated to tap water distribution systems when copper and copper alloys are the construction materials. In this context, the present paper deals with the dezincification of aluminum brass under de influence of  Pseudomona fluorescens  in drinkable water. Different electrochemical techniques such as potenciodynamic reduction curves, polarization curves, polarization resistance (Rp) and impedance spectroscopy (EIS) were used. These techniques were complemented with UV-visible reflectance spectroscopy. All the experiments were carried out using artificial tap water (ATW) pH 7.6. The surface films were grown at open circuit potential for 2 hs in situ in sterile and inoculated ATW. The occurrence of dezincification associated to the presence of bacteria was reveled by the disappearance of the peak attributed to zinc in potentiodynamic reduction curves, as well as by changes in the spectra. No differences were observed between the impedance spectra with and without bacteria when these results were interpreted in terms of an equivalents circuit. The corrosion current in the different conditions (with and without bacteria in ATW) was evaluated by polarization resistance, impedance spectroscopy and intersection of polarization curves. The Rp values obtained by polarization resistance, as well as by EIS were in good agreement. The Tafel slopes were obtained from polarization curves. In the presence of bacteria an increment in the corrosion current was observed. This could be associated to an increment in the Tafel slopes when bacteria are present. This increment in the corrosion rate is coincident with the dezincification phenomenon