Biofilm influenced corrosion on cast iron pipes in reclaimed water was systemically studied using the weight loss method and electrochemical impedance spectroscopy (EIS). The results demonstrated that compared to sterile water, the existence of the biofilm in reclaimed water promoted the corrosion process significantly. The characteristics of biofilm on cast iron coupons were examined by the surface profiler, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The bacterial counts in the biofilm were determined using the standard plate count method and the most probable number (MPN). The results demonstrated that the corrosion process was influenced by the settled bacteria, EPS, and corrosion products in the biofilm comprehensively. But, the corrosion mechanisms were different with respect to time and could be divided into three stages in our study. Furthermore, several corresponding corrosion mechanisms were proposed for different immersion times. (C) 2015 Elsevier B.V. All rights reserved.