The objective of this thesis has been to develop understanding of microbiologically influenced corrosion (MIC), within the industrial context of diesel oil fuel (DOF) tanks in Royal Navy submarines. In addition, the possibility of a mitigation strategy using biotic sol-gel coatings is explored, with field trials taking place in Barrow-in-Furness (UK) and Santander (Spain) to develop knowledge surrounding biofouling. Firstly, MIC on S355 carbon steel was studied, using Desulfovibrio salexigens as a model SRB organism. This was compared to a consortium of bacteria, isolated from the DOF tank of HMS Vengeance. In both cases, electrochemical data show a non-conductive iron oxide film covering the surface developing after 12 days in sea salt solution. In growth media, a mixed film of iron oxide, iron sulfides and iron phosphate forms. Upon removal of surface films, confocal microscopy reveals pitting in all biotic samples, with the growth media having greater pitting than the sea salt solution. Furthermore, the SRB consortium shows greater pitting than the D. salexigens in both media. The consortium of bacteria were identified using 16S rRNA sequencing, with a notable absence of any species belonging to the genus Desulfovibrio, despite this genus being the mainstay of MIC research. The only culturable SRB present was of the genus Desulfomaculum. Biotic sol-gel coatings encapsulated the endospores of a number of 'protective' bacteria to study their antibiofouling properties. These coatings were applied to test panels and exposed to biofouling conditions over two trial periods of 5 and 7 months. Bacillus psychrosaccharolyticus showed the least biofouling in photographs of the panels and showed the lowest phylogenetic diversity of settled microorganisms. Bacillus baekryungensis showed the best anticorrosion performance, with no aluminium oxide spots after 37 days, and most inhibition of settled SRB.
|Date of Award||1 Aug 2022|
- The University of Manchester
|Supervisor||Dirk Engelberg (Supervisor) & Nicholas Stevens (Supervisor)|
- Carbon Steel