Efficacy of silver-copper ions in controlling microbial corrosion related with mixed-species biofilm

摘要

The aim of this work was to determine the changes in the biofilm structure in the presence of Ag-Cu ions and how these changes in the biofilm affected the corrosion behavior of galvanized steel by electrochemical methods. The experimental study was performed using a 100-L polypropylene cooling tower model system. Galvanized steel was used as test material. After placing the coupons, the model system was operated continuously for 6 months. The coupons, which were removed from the model system every month, were immersed into the beaker containing model system water with Ag and Cu ions. The working solutions were mixed with magnetic stirrer (150 rpm) and kept at 30°C in a laminar flow system over 504 h. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization methods were used to determine the microbial corrosion behavior of galvanized steel in the presence of Ag-Cu ions. Electrochemical measurements were taken at certain times during 504 h of exposure times. SEM observations were carried out. It was observed that the biofilm structure and corrosion behavior of galvanized steel changed according to the exposure times to the Ag-Cu ions. The altering structure of the biofilm may result in changes in the effects of Ag-Cu ions on the corrosion behavior of galvanized steel. In all these findings, it can be said that the maximum concentration values of Ag-Cu ions suggested by the Environmental Protection Agency (EPA) may not be sufficient to prevent MIC of galvanized steel for long-term applications.