BACTERIAL-COLONIZATION ON METAL-SURFACES IN ANIMAL BUILDINGS - IMPLICATIONS FOR MICROBIAL-INDUCED CORROSION

The corrosion potential of steel products exposed in animal buildings caused by microorganisms was investigated by determining the presence of bacteria on metal surfaces. In an initial study, scrapings (1 g fro m sample surface) of several corroded metal samples collected from thr ee different animal buildings were cultured for total aerobic, anaerob ic, and sulfate-reducing bacterial counts. The data obtained revealed high counts (about 10(8), 10(6), and 10(4) for total aerobic, anaerobi c, and sulfate-reducing bacteria, respectively) on the corroded metal surfaces in animal buildings. In addition, the presence of biofilms on different metal samples in swine and dairy buildings were revealed by scanning electron microscopy. Data from a controlled field test (base d on 2.54 x 2.54 cm2 scrapings) showed that the anaerobic bacteria wer e able to colonize metal surfaces exposed in swine, dairy, and poultry buildings. After only six months of exposure, the counts of total ana erobic bacteria reached around 4.0 x 10(9) in the three animal buildin gs, while the counts of sulfate-reducing bacteria in all test building s were still low (less than 200). Temperature, relative humidity, ammo nia, and hydrogen sulfide levels were monitored over the six-month stu dy period. Corrosion rates were negligible for all metal types in all buildings with the exception of uncoated 1010 carbon steel in the dair y building (17.8 mum/year). Environmental measurements in this buildin g demonstrated the largest variations in temperature and relative humi dity, but the lowest ammonia concentration.