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. ....
Indian Journal of Experimcntal Biology Vol. 4 I. September 2003.
pp. 1023 -1 029
Control of metallic corrosion through microbiological route
S Maruthall1l1thll *, S Ponillari appan, S Mohanan, N Pal ani
swalllY, R Palani appan l & N S Rengasw31llY
Elcctrochemical Protec tion & Biofou ling Scct ion.
Corrosion Scicncc & Enginecring Division Central Elcc
trochemica l Research Inst itute, Karaikudi. 630 006. India
I P.G. Dept of Microb iology. Sri Paramakalyani Co llegc. A lwa
rkurichi. 627 4 12. India
In vo lvemcnt 0(' biof'i lm or microorganisms in corros ion
proccsses is widely ack nowlcdged. Although majority of thc studies
on microbiolog ica ll y induccd corros ion (MIC) have conccntrated
on ae robic/anae robic bactc ri a. T here arc nUlllerous aerobi c
b;lcteri a. which could hindcr thc corros ion process. T he Illi
crobi ologica ll y produccd cxopoly illcrs prov idc thc structural
framc work for the bio f'i I Ill . Thcsc polymers combinc w ith
dissolvcd metal ions and rorm organometalli c complexes . Gcncra ll
y hetcrotrophic bactcri a contribute to threc maj or processcs : (
i) synthes is of polymers ( ii ) accumulation of reservc
Illaterials li ke po l y-~- hyd roxy butratc (iii ) producti on of
high Illolccular wcight cx tracc llular polysacchari dcs. Poly-
[3-hydroxy butyratc is a po lymcr or D( -)[3-hydroxy bu tratc and
has a Illolecu lar we ight betwccn 60.000 and 2.50,000. Some cx
trace llular polymcrs al so havc highcr molecular weight s. It sec
ill s that highcr molccular weight polymer acts as biocoating. In
the prescnt rev icw, rolc or biochemi stry on corros ion inhibiti
on and poss ibiliti cs or corrosion inhibiti on by vari ous
microbes arc di scussed. T he ro le of bacteri a on cu rrcnt demand
during ca thodic protecti on is also debatcd. In add ition. some or
the signi ficalll contribu tions madc by CECRI in thi s proilli
sing arc;) arc highligh ted.
Keywords: Bioril lll, Corros ion contro l. Heterotrophic bacteri
a. M eta lli c cormsion
Solid surfaces immersed in aqueous environments absorb organic
matter from the surrounding environment. Bacteri a through their ex
tra ce llular metabolites cause the formati on of an ex tremely
complex micro layer called sl i me or biofi I m. The involvement of
biofilm or microorganisms in corrosion processes is 'Nell known.
The microorgani sms can promote corrosion in different ways by
differential aerati on celli . extra ce ll u lar pol ymcri c
substances2.3, or by their binding capability w ith metal i o n s~
-6. According to the more recent studi es by researchers, certain
speci fic microorganisms which favour the fo rmati on of pass ive
film on the metal surfacc could ac tu all y hinder the corros ion
process. But no detailed study is available on microb iolog icall y
induced corros ion control (MICC) systems. Thi s prov ides a vast
scope for deve loping corros ion control techniques through
microbio log ical route.
Process of corrosion control hy hacte.-ia A biofilm can contain
diffcrcnt types o f bac tcri a,
viz. (a) heterotroph ic bacteria (b) sui phate reduci ng bacteri
a, (c) thi osulphate ox idi zing bacteria and (d) manganese ox idi
zing bacteria . The ac ti ve contri butor in a biol'ilill is
heterotrophi c bactcri a. which utili ze encrgy 1'1'0111 carbon
source. T hcse hetcrotrophi c bactcri a contri bute to three maj or
processes.
*Corrc,;pulldent author: [ -mail: lllarutila_lll
@yahoo.colll
I. Synthes is o f polymers (anaboli sm) 2. Reserve material s (s
torage) 3. Cataboli sm
More th an 95% of the cellular mater:al of E.coli and other
microorgani sms consists of macromolecules. A typica l an alys is o
r microbial ce ll s gil OOg o f dri ed ce ll s 7 is as fo llows :
protei n 52.4 . polysaccharides 16.6, lipid 9.4, RN A 15.7 , DNA
3.2. These constitucnts havc their own di stinct role in
controlling metalli c corrosion. Bacteri a do not accumulate lipids
as reserve materi al but they conta in considerable amounts of
lipids especiall y phospholipids and glycolipids as constituents of
their membrane systems. These phospholipids are ncgati ve ly
charged. Whil c g lucose serves as growth substrate for E.co/i , a
nUlllber of hexose and pcntosc phosphates are intermediates in the
brcakdown or thi s substrate. Phosphates arc also negati ve ly
charged. Hence, it bccomes easier fo r the positi ve ly charged
metal ions to combine w ith ph osphates and form protecti ve
organometall ic complex .
Synthesis of polymers It has been mentioned that about 97% or
the
ce llul ar matcri al are macromolecules. Three groups can be di
stinguishcd, viz. (a) lipids. (b) peri od ic macromolecules Stich
as peptidog lycan. polysaccharides and (c) macromolecules sllch as
nucleic ac ids aile!
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1024 INDIAN J EXP BIOL. SEPTEMBER 2003
proteins. Many microorganisms excrete polysaccharides which may
be retained as part o f the ce ll structure. The macromolecules may
become dispersed in the liquid phase or in the presence of a suitab
le solid substrate. may adhere to immersed surfaces to form an
organic film .
Lipids are not true macromolecules, as the monomers are not
linked to one another by covalent bonds. However, in aqueous
environment phospholipid molecules such as phosphatidyl choline
associate in such a way that a double layered structure is formed.
M embrane contains up to 60% of protein ; some are embedded in the
lipid layers and have specific functions in the vari ous transport
processes. Peptidog lycan is the ce ll wall wh ich is synthes ized
from two building blocks: UDP - N - acetyl muramic ac id,
pentapeptide and UDP - N - acety l glucosamine. The formation of
these compounds in the cy top lasm is transferred to a membrane
lipid carri er - undecapreny l phosphate. It is then linked to N -
acety l glucosamine. Thi s di saccharide pentapeptide is
transferred by the lipid carrier to the ex trace llu lar si te o f
the cell membrane and used on a building block In peptidog lycan
chain elongation. Bes ides these. molecules of fa tty ac ids are
linked to glucosamine disaccharide of lipid throu gh ester and
amide linkages.
Bacteria differ in the reserve material they accumulate under
certain cond itions. Polyphosphate accumulati on is widespread
among bacteria. It essentia ll y fu ncti ons as a phosphorus
storage material and is utili zed for nucleic ac id and
phospholipids synthesis under conditions of phosphate starvation
.
Besides, glycogen and po l y- ~-hydroxy butyrate serve as energy
storage compounds. Pol y-~-h ydroxy butyrate (PH B) is a typical
prokaryo ti c storage materi al. It IS widespread in bacilli , in
chemolithotrophic and phototropic bacteri a, and in Pseudolllonas
sp. PHB is a pol ymer of 0 (-)~-hydroxy butyrate and has a
molecular wei ght between 60,000 and 2.50,000. It is accumulated in
the cell s of granul es surrounded by membranes. Under appropri ate
conditions, bacterial ce ll s may accumu late
so much Poly-0-hydroxy butyri c acid (PHB) that accounts for
approx imately 60% of their dry weight R. Alcaligenes sp
accumulates up to 80% of its dry weight as polymer. In eubacteri a
the synthes is of large amounts of PHB IS tri ggered by different
environmental stimuli including limitat ion o f oxygen, nitrogen.
phosphorus and potass ium individuall y or
collectively depending on the organism9.IO. Propionic and
pentanic acids are required as substrates in the
production of poly -~-hydroxy butyri c co -~-hydrox y valoric
acid. Since it has high molecular weight, it is possible that the
compound may act as a very gooe! bio-coating. Pagel I has described
the iso lation of a mutant strain of Azotobacter villelolldii,
which rapidl y produces large amounts of PHB.
Production of siderophores Escherichia coli develops four
different Fe'+
chelator transport systems wh ich are termed siderophores. It
occurs in all aerobic and facul tati ve anaerobic microorganisms.
In gram negativc microorganisms, specific receptor proteins arc
present fo r the siderophorcs in the outer membrane. It may ac t as
inhibitor particularly in acid mediull1.
Enzymes Nitrate reducer is a molybdenulll containing
membrane bound enzyme which reduces nitrate to nitrite. Mol
ybdenum is present in thi s cnzy me in the form of the so called
molybdenum co factors (M o Co) in which molybdenum is bound to a
protein moiety, the so ca lled molybdopterin Mo Co i - non cova
lent ly bound to the protein and its func ti on is th at o f a
prostheti c group. It is interes ting th at thi s co fac tor occurs
in allmolybdoprotein except th e nitrogenase in which one type of
subunit is a molybdenum iron-sulphur proteinH Besides nitrate
reducers, molybdenum cofactor has been detec ted in format dehyd
rogenase. ulfite ox idase, Xanth ine dehydrogenase, trimeth ylami
ne - n-ox ide reductase, and co-ox ides . It is poss ible to
inhibit the producti on o f hydrogenase enzyme by molybdate. I t is
also well known that sulphate reducing bacteria can accclerate
corrosion by conversion o f sulphate to sulphide in presence of
hydrogenase enzyme. By USIn g appropriate nutrient, it is poss ible
to control the production of hydrogenase enzyme thereby nulli fy
ing the effect of sulphide conversion. On th e other hand, sulphate
reducing bacteri a w ill be made to form protecti ve f ilm which wi
ll be tenaciou s and adherent.
Metal ion and exopolymer interaction Microorgani sms growIng on
water -immersed
metal surfaces form biofilms that are held together by extra
cellular po lymeri c substances (E PS) or biopol ymers. Widespread
ev idcnce indicates th at many ex tra cellular polymcrs produced by
bacteri a arc acidic and contain fun cti onal groups that easil y
binel
+
-
MARUTHAM UTH U et al.: CONTRO L OF M ET ALLIC CORROS ION
1025
metal ions in natural environment. T he naturall y formed
biofilms can be strengthened by additi on of appropriate nutrients
so as to fo rm a tenac ious and adherent protective film on the
meta llic substrate. A direct benefi ci al effec t of thi s .
approach will be a considerable reductio n in the current
requirement of cathodicall y protected structures, since the tenac
ious f ilm being less porous will reduce the cathodic area and lead
to lesser current demand fo r cathodic polari zation. Thus thi s
approach may prove to be an energy sav ing system in the case of
cathod ic protection.
International status On ly few references are avail able w ith
regard to
corros ion control by microorgani sms I2. IS. The protective
action o f Serratia marcescens on alumini um has been reported .
These po lymers combine with corrodib le meta l ions and fo rm
organometa llic complexes. These meta llexopo lymer complexes in
biofilm prov ide sites for d iffe rentia l aerati on cells 16 and
anaerobi c zones fo r the growth of SRB 14 . Many workers have
examined the ro le of bacteri a l exopolymers in meta l bindingS by
many ways . Differenti al binding abi liti es he lp to es tabli sh
io n concentratio n ce lls3.S.17 Bacte ri a l film can prevent d
iffusion of corros ion species such as oxygen to the metal surface
thereby reducing the corros ion rate. The similar reduction in
corros ion of a luminium and copper obtained by the two di ffe rent
biofilms (Bacillus brevis and Pseudomonas Jrag i) suggests that the
protection of these meta l surfaces is a general phenomenon which
occur due to oxygen removal. Pederson and Hermansson 18 fo und that
protection was caused by cellul ar metabo li c activity. The gram
positi ve bacteria excretes hydrophobic mycolic ac ids to its
exterior, whereas the oute r membrane of the gram-negati ve
consists mainl y of hydrophili c lipopolysaccharides, probably
covered with prote in8 . Besides , these same gro ups produce "Vi
vianite" formation which inhibits corros ion 19. Syrett el al.
20
reported that the genetica lly eng ineered bacteri a can release
corrosion inhibiting compounds or antimicrobi al compounds. Ornek
et al.2 1 observed that the Bacillus subtilis biofilm reduces the
corros ion rate of the passive aluminium alloys at pH 6.5. Vorster
and Wanders22 emphas ized the need fo r non tox ic environmentally
beni gn compounds such as deri vatives of naturall y occurring po
lysaccharides, acetyl amines that can protect meta l aga inst
cOITosion. Corrosion inhibition by neutrali zatio n of corros
ive
substances is re lated to the corrosIOn inhibition of mi ld stee
l by aerobic bacteri al biofi Ims under flow conditions23 .
CECRI's contribution on corrosion inhibition 1 74 2S h · d
Maruthamuthu et a .-. suggested t at Improve
pass ivity of meta ls could be attributed to negatively charged
cell wa ll s of bacte ri a . 1t was shown that reducti on in anodic
current (ip) is accomplished by pass ivato rs present within the
biofilm. The actua l concentrati on o f potenti al pass i vato rs
such as phosphates and nitrate have been measured in the bi o fi
1m. Bes ides, Mohanan el al. 26 observed t.hat biofilm reduces the
growth of inorgani c phase but promotes the formatio n of organo
meta llic complex thus improv ing the pass ivity of metal. Recently
Po nmari appan et al.27 noticed that Pseudomonas maltophilia and
Serratia sp. inhibited (communicated) mild stee l corros ion by
about 5 times. It can be seen fro m Table I that CEC RI has identi
fied ] 0 bacteri al species whi ch can confe r e ffective corrosion
protecti on and ra ise the durab ili ty of stee l substrate by
diffe rent fac tors rang ing fro m 1.1 7 to 5.3328 . T hey have a
lso establi shed for the first time that gram negati ve stra ins
have mo re inhibiti ve capab ili ty than gram positive stra ins
(Tabl e ] ). All the bacteri a studied have corros ion inh ibiting
property but to va ry ing degree. The reason fo r the more inhi
bitive capac ity by negati ve strains is the presence of phospho
lipids in the ir cell wa ll when compared to positi ve strains.
Hence, it can be concluded that it is poss ible that improvement of
cell wa ll may inhib it the corros ion. The corros ion rate is acti
vation contro lled and not diffusio n controlled. Hence it can be
concluded that the inhibiti ve bacteri a act as "anod ic
inhibitor". Since the literature ava ilable o n the ro le of
enzymes in biologica lly inhibiting corrosion can be said to be
nearl y scarce, investigati on has been done
Tab le I - Corrosion Inhi biti ve properly of various st rains
in 1000 ppm ch loride en v i ronment2~
S.No. Bacterial spec ies Corrosion rate Durability (mpy)
factor
I. Actionobacillus lignieresii 0. 1597 3.44 2. Actinobacter
calcoaceticus 0. 1303 3.83 3. AcinelObacter radioresistens 0. 1030
5.30 4. Bacillus arnyloliquefaciens 0.3299 1.87 5. Bacillus brevis
0.5283 1.1 7 6. Escherichia coli 0. 11 72 4.60 7. Kluyvera
cryocrescens 0. 1383 4.76 8. Pseudomonas aureofaciell s 0.2022 3.
10 9. Salmonella typhimuriwll 0. 11 52 4.78 10 Xanthomonas
campestris 0. 103 1 5.33
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1026 INDIAN J EXP BIOL, SEPTEMBER 2003
by using a-amy lase enzyme in presence of Pseudomonas pUlida and
Bacillus amyloliquefaciens. Polari zation study indicated that both
Pseudomonas pUlida and Bacillus allly /oliquefacieJl s act as ca
thod ic inhib itors. The impedance behav iour of mild steel with
and without vari ous bacterial species is shown in Figs 1-6.
E N
300 0--01 st day D--
-
MARUTHAM UTHU el al.: CONTROL OF METALLIC CO RROSIO N 1027
inhibition has also been observed in presence of Vibrio sp.
which leads to solubili zati on of inorganic phosphate by the
producti on of organic acid and conversion of the same as free
phosphate ions which may get adsorbed on the materi a l and inhibit
the corrosion29 . The immobili zed strains o f BaciLLus brevis,
Xanthomonas campestris have also been identified as good corros ion
inhibitive spec ies.
Influence of fresh water heterotrophi c bacteria on rei nforced
concrete has a lso been studied30 . whereas the presence of HB in
the surrounding medi um adversely affects the compressive strength
of concre te due to the destructi ve action of g lucose derived
,fro m bacterial act ion, polarization study (Figs 7 & 8)
revealed that microbes improves the passiv ity of
-500
-> E .700 -"
-900
Fig. 7 - Tafel '. plOl showing relation of cun'ent(l) with
potential (E)
80r---------------~---------,
o
-80
> -160 ~:::~~~e
E ·240 .3' ~·320 .... z W·400 .... o 0. .4eO
~60
-640
0·1 1-0 10 CURRENT,)lA
100
Fig. 8 - Potentio dynamic pol ari zation for reinforced steel in
presence and absence of Heterotrophic bacteria
re inforcing steel by adsorpti on of organic species on steel
which has been confirmed by XRD observation. The XRD pattern of
mild stee l in presence of bacterial spec ies is shown in Fig.
9.
Underground pipelines normall y traverse through diffe rent so
il strata which might be aerob ic or anaerobic in characte r.
Cathodic protection is one of the well known techniques of
protecting pipeli nes against so il corrosion. Various standards
(NACE standard , DN V standard) suggest that maintaining the
potentia l of pipeline at hi gher negati ve va lue (-950 m V vs C
U.CUS04) is needed in anaerob ic environment. Recently CEC RI has
estab li shed that Pseudomonas sp. and Vibrio sp. dramatically
reduces the current demand at va rio us potenti als during cathodic
protectio n. These bacteria are organi c nutrients utili zing bacte
ri a , while attaching on struc ture, the first attached cell s may
became less acti ve ce ll s because oxygen reduction may be hi gher
on cathodi c surface. At the same time, these groups consume
hydrogen formed at cathodic surface (Table 2) . The possible routes
of corros io n inhibiti on through the microb io logically secreted
products is graphica ll y represented in chart form.
..... C)
JC -r:1 ~ .. 0.
'C 0
C) 0 ~ L- 0 &l ~
10 30 D iffracti on angle 29 /deg.
Fig. 9 - XRD patterns o f thin film s on re inforced steel speci
men
Table 2 - Current demand during cathodic protection in presence
of bacteri al spec ies (Ponmariappan el {//.) .1 1
Control
Potenti al (mY vs SC E)
-700
-800
-900
- 1000
- 11 00
1000 ppm (chloride
a lone) (~lA. cm '2 )
15 ± 2
28 ± 3
32 ± 3
28 ± 2
68 ± 4
3% nutrient s 1000 ppm chloridc
().lA.cn,-2)
16 ± 2
26 ± 2
30 ± 3
30 ± 3
69 ± 5
Bacte ri al species
Pseudomo nas Vibrio sp. ().lA.c m·2) ().lA .cm,2)
2 ±O. I 2.0 ± 02
3 ± 0 .1 4.0 ± 0.5
5 ± 0 .1 5.5 ± 0.5
7 ± 0 .2 6.0 ± 0.5
25 ± 2.0 16 ± 2.0
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1028 INDIAN J EXP BIOl, SEPTEMBER 2003
l CORROSION ) I
I
Microbiologically
J
Microbiologically Induced corrosion (MIC) inll uenced
corrosion
control (MICC)
I ..L ,
Manganese Iron Acid SRB Heterotrophic bacteria oxidising
bacteria ba cteria Producing
Bacteria
I
l Organometallic com plexes
l Reserve mat~rial l Extracellu lar polysa ccharides 1 l
Capsular J l Slime Polysaccharide
J ( Polyphosphate ) ( Glycogen PHB Polysaccharide
L, ~ I ~ ( I
l Biocoaling J Chart 1- Microbiological route for corrosion
control
Conclusion The present review clearly shows that there is
vast
scope for developing newer technologies of controll ing metallic
con'osion through microbiological route. Heterotrophic bacteria as
a class are capable of developing a tenacious and adherent
biocoating on the meta l surface which can confer efficient protect
ion. In thi s regard, production of high molecular weight
polysaccharide becomes very important. The fact that molecular
weight can be as high as 2 ,50,000 makes thi s approach quite
promising.
Another aspect is the infl uence of gram negative strains on the
durabi lity factor. CECRI has identified some species which can
give a durabi lity of five and more in 1000ppm ch loride. This
observation cou ld be quite usefu l in extending the life of the
water pipelines . The future R&D efforts should concentrate on
ensuring sustainability.
CECRI'S observation that certa in bacteria can actually reduce
the current demand for catho lic protection is bound to have a
benefic ial impact on cost of cathodic protection. Large scale fie
ld data are to be generated for assess ing the actua l economic
impact.
Acknowledgement Thi s research was supported by the Department
of
Science and Technology, New Delhi. The authors are thankful to
the Director, Central Electrochemical Research In stitute, Karaikud
i for giving perm ission to commun icate the rev iew paper. One of
the authors
(S.Ponmarippan) expresses his sincere thanks to CSIR, New Delhi
for the award of SRF.
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