Study of MIC impact in a full-scale ship ballast tank

Microbiologically influenced corrosion (MIC) of steel is a serious problem in the marine environment and many industries, such as the shipping industry. While electrochemical measurements such as impedance have been used in corrosion monitoring for several years, the true capabilities of the technique and the optimal methodology for extracting useful information from the collected data combined with microbiological techniques, are now becoming clear. A new approach was made by using an experimental full-size practical ship ballast tank (SBT) to study the impact of MIC. Working electrodes were immersed at two different height levels of the SBT sediment and immersion zone) to model the corrosion behavior of carbon steel exposed to natural seawater in these specific zones. Until now little information is available on microbial community composition and the corresponding corrosiveness within ship ballast tanks. PCRDGGE analysis was performed to characterize the microbial community near the sidewall of ship ballast tanks as well as the water phase. The information was combined with conventional electrochemical on-site measurements such as OCP and LPR to evaluate corrosion initiation by bacterial communities in closed seawater environments like ship ballast tanks. Substantial corrosion could be monitored by LPR, indicating a clear difference in corrosion behavior for bottom and immersion zone related to the variation of bacterial population. This research paper summarizes for the first time the problem of attached biofilms in the field of corrosion in ship ballast tanks combining electrochemical and molecular analyzing tools.