Abstract
Microbially influenced corrosion (MIC) is a major problem in various sectors including chemical process plants, on-shore and off-shore oil and gas, pipelines, marine and aviation industries resulting in annual losses just in the United States of several billions of dollars. MIC often develops as a result of biofilm formation by multiple microbial species that form well-defined and organized structures. Development of effective mitigation strategies for MIC requires a fundamental understanding of how biofilms are formed. The aim of this study was to investigate the factors underlying formation and development of dual-culture biofilms. Using Vibrio natriegens as the model biofilm forming species and Shewanella oneidensis as the model iron reducing bacterium, we investigated the dynamics of biofilm formation using a microfluidic flow cell. The experimental system consisted of a flow channel in a microfluidic device made of polydimethylsiloxane that is bonded to a glass slide with coated metal electrodes. The effect of hydrodynamic factors like flow rate was investigated on single species biofilms in this system. Later, co-culture biofilms of V. natriegens and S. oneidensis developed in this system were used to measure biomass in the biofilm by confocal laser scanning microscope (CLSM) and impedance from electrochemical impedance spectroscopy (EIS). These parameters measured were analyzed along with SEM images of the metal electrodes to give an understanding of the extent of MIC from a biofilm perspective.
Introduction
Microbiologically influenced corrosion (MIC) is a corrosion process in which microorganisms play a significant role by actively getting involved in redox reactions occurring at the site of corrosion. MIC is a major problem seen across various chemical process industries, on-shore and off-shore oil and gas industries, pipeline industries, marine industries and aviation industries.¹ According to a survey by the U.S. Federal Highway Administration (FHWA), the direct corrosion costs in US from 1999 to 2001 amounted to $276 billion; and when indirect costs are conservatively taken into account, the result will be 6 percent of US GDP.² Another study estimates that the activity of micro-organisms is the reason for around 20 percent of pipeline corrosion.³ These numbers associated with the costs and wide prevalence of MIC gives us an idea of the extent of this problem and the necessity to effectively mitigate MIC.
