MICROBIAL COLONIZATION OF THE SURFACE OF STAINLESS-STEEL COUPONS IN A DEIONIZED WATER-SYSTEM

Stainless steel coupons immersed in a deionized water system for about 7 months were analyzed for the presence of biofouling and microbially-influenced corrosion bacteria. Aerobic oligotrophs were dominant while other microorganisms including sulfate-reducing bacteria were present in relatively low numbers or were absent. A wide variety of microorganisms were detected on the coupon surfaces by scanning electron microscopy. The growth of microorganisms was patchy and in the form of small colonies attached to the surfaces with a confluent film of extracellular polysaccharide or fine strands. Corrosion products, such as sulphur, could not be detected. The potential for biofouling and microbially-influenced corrosion exists in the deionized water system since oligotrophic microorganisms would multiply and form a biofilm in which conditions conducive to the growth of microbially-influenced corrosion bacteria could be created.