The role of biofilm in maturation process on microbial corrosion of galvanized steel

摘要

The main aim of this study was to determine the role of biofilm in maturation process on the microbial corrosion of galvanized steel surfaces in a model recirculating system. It was also aimed to observe changing in structure of the biofilm during the maturation process. The experimental study was performed using a 100-L polypropylene cooling tower model system. Galvanized steel coupons were placed in the model system and the system was operated continuously for 6 months. The coupons were removed from system firstly after 0.5 h and then every month. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization methods were used to determine the microbial corrosion behavior of galvanized steel. The biofilm and corrosion products on the galvanized steel surfaces were investigated by using Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectrometry (EDS). It was observed that the variations in structure of the biofilm affect the corrosion behavior of galvanized steel. The maximum corrosion rate of the coupons was determined as 19.6 mpy at 1st month and then a significant decrease was observed in the corrosion rates. The results of EIS experiments and surface analyses showed that the structure of the biofilm changed over the experiment. It suggests that the biofilm has a dynamic and complex structure.