effects of sulphate reducing bacteria (SRB) on pitting corrosion of Type 304 stainless steel in nearneutral
solutions based on 0.1 M NaCl have been studied at ambient temperature. SRB are considered to have at
least two potentially corrosive effects: they create a biofilm having a crevice like geometry on the metal surface
and they produce hydrogen sulphide. Slow potentiodynamic scans were used to measure pitting potentials and pit
current transients in 0.1 M NaCl solutions with and without H,S, a modified Postgate growth medium inoculated
with SRB, and an inorganic medium based on the Postgate medium. Measurements were made after an 8 day
incubation or aging period. Results indicate that although H,S enhances pitting corrosion, SRB have less effect
on the pitting potential than would be expected from the levels of H,S they produce. In fact, a decrease in the
metastable pitting rate was observed suggesting that, rather than forming aggressive crevice environments in these
tests, the biofilms had inhibitory properties. Analysis of current transients in terms of the pit stability product
suggested that pits in commercial grades of stainless steel should possibly be considered as micro-crevices rather
than ideal hemispherical cavities. 0 1998 Published by Elsevier Science Ltd. All rights reserved
effects of sulphate reducing bacteria (SRB) on pitting corrosion of Type 304 stainless steel in nearneutralsolutions based on 0.1 M NaCl have been studied at ambient temperature. SRB are considered to have atleast two potentially corrosive effects: they create a biofilm having a crevice like geometry on the metal surfaceand they produce hydrogen sulphide. Slow potentiodynamic scans were used to measure pitting potentials and pitcurrent transients in 0.1 M NaCl solutions with and without H,S, a modified Postgate growth medium inoculatedwith SRB, and an inorganic medium based on the Postgate medium. Measurements were made after an 8 dayincubation or aging period. Results indicate that although H,S enhances pitting corrosion, SRB have less effecton the pitting potential than would be expected from the levels of H,S they produce. In fact, a decrease in themetastable pitting rate was observed suggesting that, rather than forming aggressive crevice environments in thesetests, the biofilms had inhibitory properties. Analysis of current transients in terms of the pit stability productsuggested that pits in commercial grades of stainless steel should possibly be considered as micro-crevices ratherthan ideal hemispherical cavities. 0 1998 Published by Elsevier Science Ltd. All rights reserved
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effects of sulphate reducing bacteria (SRB) on pitting corrosion of Type 304 stainless steel in nearneutral
solutions based on 0.1 M NaCl have been studied at ambient temperature. SRB are considered to have at
least two potentially corrosive effects: they create a biofilm having a crevice like geometry on the metal surface
and they produce hydrogen sulphide. Slow potentiodynamic scans were used to measure pitting potentials and pit
current transients in 0.1 M NaCl solutions with and without H,S, a modified Postgate growth medium inoculated
with SRB, and an inorganic medium based on the Postgate medium. Measurements were made after an 8 day
incubation or aging period. Results indicate that although H,S enhances pitting corrosion, SRB have less effect
on the pitting potential than would be expected from the levels of H,S they produce. In fact, a decrease in the
metastable pitting rate was observed suggesting that, rather than forming aggressive crevice environments in these
tests, the biofilms had inhibitory properties. Analysis of current transients in terms of the pit stability product
suggested that pits in commercial grades of stainless steel should possibly be considered as micro-crevices rather
than ideal hemispherical cavities. 0 1998 Published by Elsevier Science Ltd. All rights reserved
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