Title Biodegradation of ballast tank coating investigated by impedance spectroscopy and microscopy
Publication Type Journal Article
Year of Publication 2014
Authors Heyer, A, D’Souza, F, Zhang, X, Ferrari, G, Mol, JMC, de Wit, JHW
Journal Biodegradation
Volume 25
Issue 1
Pagination 67 – 83
Date Published 2014/02//
ISBN Number 1572-9729
Abstract This research paper addresses the biodegradation process for ballast tank coatings in marine environments. As part of this new approach, a commercially available ballast tank coating was exposed to bacteria obtained from a culture collection and to a natural bacterial community isolated from a real ballast tank. The natural community was chosen to explore the interaction of natural biofilms with the coating, an aspect, which is not covered in standard procedures. It is shown that biological activity significantly affects the coating properties. Micro-cracks and holes have been identified using AFM. Acidic bacteria generated holes with 0.2-0.9 μm in depth and 4-9 μm in width. Whereas the natural community additionally caused cracks of 2-8 μm in depth and 1 μm in length. The overall effect of this degradation was examined using the EIS technique. However, the bacterial affected coatings (exposed to acid producing bacteria and a natural community) show a decrease in corrosion resistance. Impedance IZI values decreased over time from 1.18 × 10(9) to 1.87 × 10(7) Ω for acidic bacteria and from 1.71 × 10(9) to 2.24 × 10(7) Ω for the natural community, indicating a clear loss in coating resistance over time. It is also revealed that the coating corrosion resistance declines after 40 days of exposure for the natural community, leading to the formation of blisters. Bacterial settling could be linked to some specific biofilm patterns affecting different types of coating attack. It can be concluded that it is necessary to include natural communities in coating degradation studies to identify possible degradation mechanisms and the severity of the attack over time.
Short Title Biodegradation

 

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