Above ground, heating fuel oil tank: 935 litres (approximately 200 gallons)
ASTM A569 (or equal) sheet steel.
The heating fuel oil tank had been in service for approximately three years.
The observed corrosion features were found to be dissimilar to typical corrosion pitting. Pitting was found to be highly localized, and appeared as straight, bore-like holes, in contrast to typical concave pitting. Additionally, tunnel-like features were observed below the corrosion pits within the wall thickness of the tank. It was determined that the corrosion perforations that caused the above ground heating fuel oil storage tank to leak were caused by microbial influenced corrosion (MIC). MIC is the corrosion or deterioration of a material which is initiated and/or accelerated by the activities of micro-organisms.