Effect of Corrosion Media on Biofilm Detachment and the Corrosion Mechanism of Serratia marcescens on Carbon Steel in River Water

The bacterial biofilms formed on metal surfaces play an important role in the corrosion of the metal. Biofilm detachment can greatly influence the corrosion rate. Since the biofilms formed by certain strains of Serratia marcescens are known to get sloughed after prolonged surface exposure, studying the effect of corrosion media on this phenomenon and the corrosion rate will help in understanding the corrosion mechanism of S. marcescens. In this work, carbon steel was exposed to multiple systems containing S. marcescens isolated from treated river water used as a coolant in an oil refinery, referred to as industrial water (IW). The bacterial cultures were anaerobically cultivated in the American Petroleum Institute (API) growth medium and identified using 16S rRNA gene sequencing. Biofilm morphology was assessed through Light microscopy and Confocal Laser Scanning Microscopy (CLSM). The conditions required for biofilm sloughing were investigated by electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, weight loss and surface morphological studies in four different media. While sterilized IW served as a control, biofilm detachment occurred during polarization studies only in the system where the metal sample was exposed to IW containing S. marcescens and the API medium. However, detachment did not occur during other analyses and in similar systems without the API medium or when nitrate ions were added to the API medium. Based on these observations, the mechanism adopted by S. marcescens for its growth and the corrosion of carbon steel under various conditions could be elucidated.