The effects on microbiologically induced corrosion (MIC) of mild steel resulting from the presence of corrosion products in the biofilm of sulphate-reducing bacteria (SRB) have been investigated. The culture-media-containing sulphide of biogenic origin was used to find out the effect of metal-sulphide layers developed. The SRB were isolated from the Ennore brackish water (Chennai, India). Biocides with different concentrations were used to inhibit the metabolic activity of bacteria. Open circuit potentials (OCP) followed by potentiostatic polarisation measurements were carried out for the specimens with and without the biofilm. Electrochemical impedance spectrometry (EIS) and scanning electron microscopy (SEM) were used to study the accumulation of the biofilms. The corrosion rates and the mechanism of corrosion processes were understood from the investigation.