The involvement of sulphate-reducing bacteria in a heterogeneous marine laboratory model
Sulphate-reducing bacteria are known to play an important role in anaerobic corrosion processes. They are often found associated with metal surfaces and their activities can be of particular economic significance in many industrial areas. The aim of this thesis was to investigate anaerobic corrosion of metals by the sulphate-reducing bacteria in the presence of mixed microbial consortia in various heterogeneous marine environments. A laboratory model system was designed, based on part of an offshore oil storage system. An extensive bacteriological analysis and comprehensive study of the consequent physicochemical parameters involved in the microbial corrosion process was carried out. Particular attention was paid to the activity of the sulphate-reducing bacteria on metal surfaces. A method was developed to measure both acid-volatile and non-acid-volatile sulphur formation, produced by the activity of the sulphate-reducing bacteria on mild steel coupons. The importance of this method is firmly stressed. Previous results involving rates of sulphate reduction estimated without considering non-acid-volatile sulphur product formation, must be interpreted with caution. A study of non-biological methods of analysing corrosion and their various limitations was carried out to assess their usefulness in determining the effect of microbial corrosion in various environments. It must be stated that no single technique can be used to study anaerobic microbial corrosion. Therefore, it is recommended that a series of tests should be utilised. These should include microbiological, chemical and metallurgical methods.