International Journal of Minerals, Metallurgy and Materials
Volume 19, Number 8, Aug 2012, Page 717
DOI: 10.1007/s12613-012-0618-y
Corresponding author: Fu-shao Li E-mail: lifushao@126.com
© University of Science and Technology Beijing and Springer-Verlag Berlin Heidelberg 2012
Corrosion inhibition of stainless steel by a sulfate-reducing bacteria biofilm in
seawater
Fu-shao Li
1,2)
, Mao-zhong An
3)
, and Dong-xia Duan
2)
1) School of Chemistry and Chemical Engineering, Qujing Normal University, Qujing 655011, China
2) State Key Laboratory for Marine Corrosion and Protection, Qingdao 266071, China
3) Chemical Engineering School, Harbin Institute of Technology, Harbin 150001, China
(Received: 30 June 2011; revised: 14 September 2011; accepted: 19 September 2011)
Abstract: Corrosion inhibition of stainless steel due to a sulfate-reducing bacteria (SRB) biofilm in seawater was studied. By atomic force
microscopy, a layer of fish-scale-like biofilm was found to form as stainless steel coupons were exposed to the culture media with SRB, and
this biofilm grew more and more compact. As a result, coupons’ surface under the biofilm turned irregular less slowly than that exposed to
the sterilized culture media. Then, physicoelectric characteristics of the electrode/biofilm/solution interface were investigated by electro-
chemical impedance spectroscopy (EIS), and the coverage of the biofilm as well as the relative irregularity of coupons’ surface was also re-
corded by EIS spectra. Finally, anodic cyclic polarization results further demonstrated the protective property of the biofilm. Therefore, in es-
timation of SRB-implicated corrosion of stainless steel, not only the detrimental SRB metabolites but also the protective SRB biofilm as well
should be taken into account.
Keywords: stainless steel; corrosion prevention; microbiology; microorganisms; biofilms; electrochemistry
[This work was financially supported by the projects of Qujing Normal University (Nos.TD200901 and 2009ZD009).]
1. Introduction
In aquatic environments, metals/solution interfacial elec-
trochemical properties and physical structures are often al-
tered considerably by the microorganisms’ metabolic activi-
ties [1]. Consequently, these metals tend to exhibit some
peculiar and unique corrosion characteristics, i.e. a phe-
nomenon well known as microbiologically influenced cor-
rosion (MIC). Once microorganisms like bacteria have
colonized on the surface of an object, a layer of biofilm will
eventually form. This complicated biofilm is mainly com-
posed of extracelluar polymeric substances (EPS) [2], and
the concrete compositions and structure depend not only on
the biological nature of the cells but also on the circum-
stances of their growth as well. EPS in some types of
biofilms have the high ability of complex-binding metal ions
and thus is thought to promote corrosion [3]. On the con-
trary, a biofilm resulted from given groups of bacteria can
provide the metal base with good protection, which is re-
ferred to as MIC inhibition (MICI) in the literatures [4].
In the case histories of MIC, rapid corrosion of carbon (or
low-alloyed) steel due to sulfate-reducing bacteria (SRB) in
anaerobic media has long been reported and widely studied.
From the point of cathodic reactions, the roles of SRB can
be viewed from two aspects. The first aspect is the indirect
effect of SRB via the metabolic weak-acid molecules such
as hydrogen sulfide, and on this occasion, deprotonation is
much faster than that merely from water [5-7]:
22
Fe H S FeS H
→+ (1)
In the meantime, hydrogen evolution will further be
stimulated by fresh iron sulfide, which acts as a good cath-
ode with low hydrogen overpotential when coupled with the