Incidence of microbial corrosion of metallic tubes in sanitary facilities

摘要

Metallic alloys such as galvanized steel and copper tubes are used in sanitary water distribution systems for their corrosion resistance. In the last decades, corrosion rates found in sanitary facilities using galvanized steel pipes have exceeded the expected values, shortening their lifetime. Following some assessments, the hypothesis of microbial corrosion has been put forward. This corrosion may be attributed to sulphate-reducing bacteria (SRB), which reduce sulphates contained in water, turning them into sulphides and acidifying the environment. This work aimed to define the role of SRB as an aggravating factor in the usual corrosion mechanisms. The principal purpose was to characterize the chemical influence of the biofilm present on metallic substrates (carbon steel, pure zinc and pure copper) by studying the evolution of chemical and electrochemical parameters with time. Two distinct culture media were used: a sterile Baar's solution (as reference) and a similar medium inoculated by a SRB commercial strain. The evolution of the corrosion products was followed by Scanning electron microscopy and optical microscopy. The chemical composition evolution of the culture media was analysed by UV-visible spectrometry and total organic carbon method.