EFFECT OF THE SULFATE REDUCING BACTERIA BIOFILM ON PHASE BOUNDARY BETWEEN HSn70-1AB COPPER ALLOY AND SOLUTION

Growth characteristics of sulfate reducing bacteria(SRB) were tested.The SRB was in logarithmic-phase growth during the first three days and turn into stationary-phase growth since then.Atomic force microscopy(AFM) and electrochemical impedance spectroscopy(EIS) were used to investigate the effect of biofilm on phase boundary of HSn70-1 AB copper alloy and solution,respectively.The AFM images results showed that SRB cells adhered to the surface of copper alloy and the biofilm formed after three days immersion were observed.Roughness of three-day-old biofilm formed on the alloy was 44.7nm,while it decreased to 25.8nm after 14 days immersion.The simulative data of EIS spectrum revealed that capacitance value of oxidation film on the alloy surface was not significant change during the first three days immersion,which implied that the oxidation film of copper alloy was relatively stable in this period.After 7 days immersion,the oxidation film of copper alloy initiated localized corrosion and micropores appeared on the surface,which was indicated by the increase in capacitance value of oxidation film.