ABSTRACT
Microbiological corrosion has caused several damages to several industrial segments that use the metallic materials in their systems. One way of minimizing and even controlling this problem has been the biocide application in these systems. In this work, the microbiological corrosion of the UNS S 31803 duplex steel was evaluated by the application of a biocide containing quaternary ammonium salts in petroleum production water from an offshore platform, simulating the hypersaline environment. In order to evaluate the microbiological corrosion, microbiological technique as Most Probable Number method (MPN) and electrochemical technique (open circuit potential and polarization measures) were used. The biocide impacted on the present microbiota, eliminating two bacterial groups (aerobic and sulfate reducing bacteria) in the sessile phase. The highest open circuit measured potentials were observed when the biocide containing quaternary ammonium salts was applied to the systems. The potential pite values obtained by the polarization analyzes showed that the microorganisms influenced the values and that the biocide kept the potentials around 1000 mVECS. The polarization tests allowed to analyze, through instability in the curves and variations in passive current densities over time, the complex dynamics occurring on the metal surface due to competition between formation and destabilization of passive film, adsorption and desorption of biocide/biofilm.
Keywords
Duplex steel; microbiological corrosion; quaternary ammonium salts
