Microbiologically assisted stress corrosion cracking of carbon steel in mixed and pure cultures of sulfate reducing bacteria

The role of microbiological environments containing pure and mixed cultures of sulfate-reducing bacteria in stress corrosion cracking of carbon steel in biotic and abiotic environments was investigated. Carbon steel specimens were subjected to slow strain rate testing in a synthetic seawater environment (3.5% sodium chloride solution), with and without the microbiological cultures. Specimens tested in biotic (microbiological) conditions showed a considerable loss of ductility, as compared to those tested in abiotic conditions. Fractography of the specimens tested in abiotic solutions suggested features of only ductile failure (dimples), whereas those tested in biotic conditions had additional features of brittle cracking. Results also suggested the role of sulfate-reducing bacteria in promoting hydrogen-assisted cracking.