The application of XPS to the study of MIC Page: 3 of 15
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in the breakdown of passive alloys has yet to be estabiaslKed.■
sion products of unusually high concentrations of certain chemical elements that
may have a microbiological origin has been proposed to be conclusive proof: of the
role of bacteria in a degradation process. For example, the presence and activity of
SRB in water systems is often associated with the pungent odor of j\y^r°gen su ' e
and the formation of metal sulfides. Although metal sulfides ana H2S may be p
sent at a corrosion site, these factors are not necessarily the cause of accelerated co-
rosion There are both biotic and abiotic sources of sulfur compounds and H2S in
113t^aditional°models for the mechanism of SRB corrosion, such as that by von
WoLgen and Van der Vlught, do not take into consideration the differences be-
tween biotic and abiotic sulfide formation Furthermore the nature o sulfur
species formed cannot be predicted from thermodynamic datf ^rP '
Macinawite is a sulfide phase that is thermodynamically unlikely to form under
ambient conditions. Yet, MacNeil and Iittle have obs^ed.^.^^^f0rThe
bioticallv and MacDonald has observed Maanawite under abiotic conditions, the
^hysko<hemiral properties of the bacteria cell wall as well as the sulf.de must also
b8 Sve adsorption of certain metal ions by SRB and subsequent sulfide
formation has not b Jn fully investigated. The retention of metal ,ons on cd walls
by the formation of intermediate organometallic and metal-organic complexes
provides a unique means for metal ions to react with bactenogexuc sulfur.
Mohagheghi, et al., have demonstrated that metal ions bound to bacterial cell
walls are8more reactive with sulfide than are metal ions in solution. This ll ustrates
that the biotic environment is far more complex than the simple abiohc analog o
sulfur reacting on a metal surface to form a sulfide in a biotic environment.
However, there clearly exists considerable opportunity for corrosion^ result from
the direct contact of sulfur with a metal surface, especially in the presence o
sulfide that is acting as a cathodically active surface.[7-10] Newman, et al.[ll] have
demonstrated that Type 304 is more susceptible to pitting in neutral chlon
containing solutions when sulfur speaes (Na2S203, Na2S4Ofe, KSCN, Na2S,, 2 3/
“do”fm^ndfoerdthe limited characterization of corrosion products assorted with
MIC is that the nature of the chemical species within the biomass could not be pre-
tiselv determined. This may be due to one or more of the following reasons:
l Limits of detection for the technique^) employed, (e.g. SEM Energy Dispersive X
rav Analysis cannot determine the valence state of an element).
2. The small quantity of corrosion products that were analyzed (such as those that
3. hiadequate^preservatkm oftiie biological and/or chemical integrity of the
Determination of the precise chemistry of corrosion products in a biomass may help
materials [12-15] as well as the surface of living cells [19-22]. In the present studY'
amilication of the technique has been extended to study the effect of environmental
conditions on microbial behavior as well as the ability of bacteria to alter local
environmental conditions. Specifically, the interaction of Fe, Cr, Ni, Mo 10ns with
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Kearns, J.R. (Allegheny Ludlum Corp., Brackenridge, PA (United States). Technical Center); Clayton, C.R.; Halada, G.P. (State Univ. of New York, Stony Brook, NY (United States). Dept. of Materials Science); Gillow, J.B. & Francis, A.J. (Brookhaven National Lab., Upton, NY (United States)). The application of XPS to the study of MIC, article, January 1, 1992; Upton, New York. (https://digital.library.unt.edu/ark:/67531/metadc1094209/m1/3/: accessed March 18, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.