Metals immersed in natural seawater are covered with a thin, slimy film of micro-organisms and their biological secretion commonly referred to as biofilm. Biofilms cause the ennobling of the free corrosion potentials and increase the susceptibility of pitting- and crevice corrosion. Biofilm formation from Arabian Gulf water has not been reported before. Biofilm formation on 7 different types of Mo-containing stainless steels and on type 304 steel from Arabian Gulf water was examined in detail. Film formation was followed by measuring the variation of the open circuit, free corrosion potentials in fresh seawater. Stages in the potential-time curves were assigned to oxide thickening and biofilm formation. Coverage with the biofilm occured within 12-15 days of immersion and was independent of the chemical composition of the steels. Oxygen reduction on biofilmed metals was accelerated and the process involved the intermediate formation of H2O2. Cathodization retarded film growth and reduced the catalic activity of the film. Complementary anodic polarization experiments showed a change in behaviour and increased attack at the transpassive region. Biofilm formation thrived with rise in temperature till ca. 42 deg C whereafter the micro-organisms were killed. No film formed in pre-boiled and cooled seawater. Some factors influencing the activity of the biofilm were identified and examined in some detail. These comprised temperature, dryness, sterilization of the water and the eventual use of biocides.
Biofilm formation on stainless steels in Arabian Gulf water
Biofilmbildung auf rostfreien Stählen in arabischem Golfwasser
Desalination ; 107 , 3 ; 251-264
1996
14 Seiten, 10 Bilder, 1 Tabelle, 29 Quellen
Aufsatz (Zeitschrift)
Englisch
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