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DABHOLE JOISHY
:
MILD
STEEL
CORROS
ION
REDUCTION
IN
WATER
685
directions. Using Tafel extrapolation method, the
co rres ponding current was plotted
l6
. All experiments
were conducted after 30 min each from the time of
immersion of: (a) Mild steel coupon in
Thane
creek
and cooling tower water sample and (b) Mild steel
coupon
in
Thane creek
and
cooling tower water
sample
containing
Rhod
otorula mucilaginosa 10
5
ce
ll s/mL) .
Corrosion Rate Detection
by
Weight oss
Method
- A laboratory method was devi sed for
detecting corrosion rate reduction. The initial weight
of fourteen mild steel
coupons
were taken and
suspended in 1500 mL Thane creek water (pH 7 .0) in
a round bottom fla sk and
sea
led . 15 mL of
Rhodotorula mucilaginosa
( 10
5
cells/mL)
wa
s
added
to th e
water
f
rom
the side arm. A zero
hour coupon
was taken
out
from the flask.
Th
e
coupons were
incubated for
14
d. Each day
one coupon
was taken
out and
co r
ros ion rate determined. On thirteenth day,
a initially weighed mild steel coupon was inoculated
in
Thane
creek water and corrosion rate was
determined after 24 h.
Results nd Discussion
Five yeast strains were iso lated from Thane
creek and ten from Powai lake water sampl e.
Rhodotorula l11ucilaginosa
was found in
Than
e creek.
Rhodoto rula glutinis was present in Powai lake .
Glucose IS not fermented by Rhodotorula
tnllcilaginosa but assimi lati on of glucose was
observed. In Rhodotorula J11ucilagillosa, maltose and
lactose is not assimilated. Th ese res ults were found to
be s imilar to those reported as a part
of
standard
id
entification of yeasts (Table I ). The mos t common
spec ies reported in water and sediments of lake
Ontario
in
North America are Candida guillermondii
and
Rhodo{o
mla
l17Ltcilaginosa
?
In the present stud y,
it
was obse rved that
Rh odotoru
a
J11ucilagilLosa (24 h o ld) were able to
take up dissolved oxygen within 24 h
of
incuba
ti
on
in
Thane creek water No supplement was prov
id
ed to
Rhodolorula ,
except those present in water sa mple.
I?hodororu
a
u cilaginosa showed hi gh uptake of
disso lved
oxyge
n (2.8
ppm
) as
co
mpar
ed to other
yeas t spec ies (Table 2). As Rhodolom /a spec ies are
w
id
e ly found in mar
in
e water, they are accl imatized
to Thane creek environment. When cadmium chloride
was added to Thane creek water sampl e at different
concentration, the co nsumption
of
uptake
of
dissolved
oxygen was reduced due to
cadmium
tox ic ity at
30
ppm after 72 h. This shows that both Rhodotorula
Table I-Identifica
ti
on
of
RllOdotorula lIlu ciiaginosa
Te st
Fermentation
Assimilation
Glu cose
Galactose
Maltose
Sucrose
Lactose
Glu cose
Galactose
Xylose
Sucrose
Maltose
Laclose
Mannitol
Ethanol
Urea
Nitrate
Diazoni
um
Blue
B
Growth at 25 C,
30
C, 37 C
Note: Allihe tests were performed
in
triplicate sets
Resulls
+
+
+
+
+
+
+
+
Table 2 - Disso
lv
ed oxygen upt
ake
by yeas ts in
Thane
cr
ee
k
water
Yeasts Dissolved
D O uplake
oxygen (ppm) (ppm )
Hallse
ill
ospora
va
rum.
5.6
1 5
Rhodo torula mucilag
ill
osa
4.3 2.8
Debaromyces hallsellii
6.2
0.9
Ca ndida tropicalis
6.7
0.4
Saccharomyces cereviseae
5.4
1
7
Rhodotorula glutinis
5.0 2. 1
Note:
Initi al dissolv
ed
oxygen - 7. 1 mg/L
Dissolved oxygen was determined after 72 h in cubation at roo m
temperature.
species were able to take up di sso lved oxygen
in
Thane creek water below 30 ppm very ef ficiently
Studies ca rried out , us
in
g Rhodot
or
ula u ci/agi
ll
os l
in
coo
ling t
owe
r water indicated di sso lved oxygen
uptake after a pe riod of 24 h.
Th
e dissolved oxygen
uptake
by
Rhod
otorula l11ucilaginosa in
Thane
creek
water(6.9 mg
/L
) was found to be more as
compar
ed to
coo ling tower water (6. 11 mg/L) in the presence of
cadmium chloride (Table 3) .
At pH 5 the
co
rros ion rate
of
mild stee l
in
Thane
creek water reduced to 5.59 mpy from 13.6 mpy upon
addition
of
Rhodotorula mucilaginosa. The initial
dissolved oxygen (6.88 mg/L ) was declined to 5. 17
8/10/2019 JSIR 62(7) 683-689
4/7
686
J SCIIND RES
VOL
62 JULY 2003
Table 3 - Di sso lved oxygen uptake by yeasts
Water sample yeast strains time disso lved oxygen
m
/L
Without
CdC
I
With
CdC
I
2
10 ppm
20 ppm
30
ppm
Thane c reek
RllOdolO mla 24
4.8
5.2
6.1
6.9
Mllcilag ill
osa
48
4 .3
5.0
5.7
6.8
72
4.2
4.9
5.7
0. 8
RhodolOrula
24
5.6
6.0
7.0
7. 1
g
lwilli
s 48
5.4
5.8
6.7
7.0
72 5. 1
5.6
6.7
7.0
Note: pH of Th ane creek - 7. : 2 and initial di sso lved oxygen - 7.2 mg/L
Table 4 - Mild st
ee
l corros ion reduction
in Than
e cree k water by RhodolOrula IIllieilag ill
osa
(p H 5.0)
Sample
Initi al wt
of
Final wt of IW-FW of Metal uptake
Mild stee l ClJ upon+
Th
ane creek water sample
Mild steel coupon+Thane c reek water
sa
mple+C dCl
2
Mild steel coupon+Thane c reek water
sample+RllOdolorula IIllicilaginosa
Mi
ld steel
cO ll
pon+Thane c reek water
sample+CdC I
2
+
RhodolOmla
IIlll
cilagillo.w
mild steel
g)
4.407
6.4847
7. 1683
6.8023
mild steel
mild steel
g) (g)
4.4052
0.0018
6.48 15
0.0032
7. 1662 0.0021
6.8006
0.0017
Corrosion rate
(mpy)
SO
(pp m)
13.6
(0.057)
Ferrous = 8.77
12.3 (0. 152)
5.59
(0.0 1)
Ferrous =
O
157
5.95 (0.025)
CJ dmium=
I .S :
SO - The Standard Deviation is valu e
of
three indepe ndent experiments under id entical condit ions
Initia l di sso lved oxygen - 6.88 mg/L a
ndlin
al di sso lved oxygen - 5. 17 mg/L
mg/L.
The up
ta ke of
cadmium
chlorid
e ( 1.88
ppm
)
and fe rrous (
0.157
ppm) by Rhodotoru a
lIIu
ci/ag inoso sho
wed affinity
towards ca dmium
chl oride. The r
es
ult s a re pr
ese
nted
in Tabl
e 4.
At pH 7 the co rro sion rate was reduced
signifi
ca
nt ly to 1.48 mp y. It can be obse rved that
uptake of cadmium and fe rrous ions is less du e to
hi
gh
up
take
of
disso l\red ox ygen.
These
resu lts
indicate
that
the r
esp
ira ti on by
Rh
odoto
rula
ci/agillos l is a
co
ntinous process during which
cadmium ions are absorbed rapidly, as observed from
Ta b le
5
At pH 9.0, the
co
rr
os
ion rate
did
not chan ge
app rec iab ly indica tin g that alkaline pH cond ition was
not favourabl e for growth and activity
of
Rh
odoto
mLa
IIll1 ci/o ginosa. Further, alkaline
condition itse lf
is
know n to be res ponsible fo r ca using co rros ion.
[n
thi s
case, the uptake
of ca
dmium and ferrous ion s
tS
co nsiderab ly hi gher than at pH 5 and 7 (Table 6). [n
Ta b le 7, when mild
stee
l
co
upon was
inoculated
In
coo
ling
tow
e r
water
at
pH 7.0
in pr
ese
n
ce and
abse nce
of
Rh
odo t
orula
l11ucilaginosa ,
corro s ion rate
was found to be reduced by 50 per
ce
nt F igure I ).
pH 7 was fo und to be idea l for uptake of
ca
dmium and ferrous ion s by Rh
odoto
ru l
a
l11u
cila ginosa.
The
res ults indi ca te that pH pl
ays
a
c ritica l role in re
du
c
in
g co rro sion rate. In a similar
study , a protec tiv e effect of
Ps
eudomonas fragi
and
Esc
herc
hia co
li
DH5 was found to redu e co rros ion
of
stee l
6
.
A lab orat ory method for
co nfirmin
g mild
co rro sion redu ction in water showed that co rr
os
ion
d
ec
r
ease
d
from 4.4 mpy
to 0.85
I
mp
y.
The corrosion
rate dec reased pe
ri
odicall y over 14 d afte r w hi ch the
co
up on inoculated on thirtee nth
day
showed co rr
os
ion
rat e
of
0.850 mp
y. Th
e ex pe riments carried out
showed that mild st
ee
l corrosion in Th an cree k W
8/10/2019 JSIR 62(7) 683-689
5/7
DABHOLE
JOISHY:
MI
LD
STEEL CORROS I
ON
REDUCTI
ON
IN WATER
687
Ta b
le 5 - Mild steel corrosion redu ction in
Thane
creek water by Rh
od ru
la lIIuc
iia
gillosa (pH 7.0)
Sample
Initi al wt of Final wt of IW-FWof
mi ld steel mild steel mild steel
(g) (g)
(g)
Mi
ld steel co
upon+Than
e creek water sa
mple
4.8089
4.8055 0.0034
Mild steel
coupon+Th
ane creek water
4.6578 4.6546 0.0032
sample+CdC
l
2
Mi Id stee l co upon+Thane
creek water
6.4638
6.4633
0.0005
sampl
e+Rhod ru
ia IIIl c
il a
gillosa
Mild steel
coupon+Thane
creek water
7.0571
7.0565 0.0006
sample+CdCl
2
+
Rh
od m la IrIllciiagillo.m
SD - The Standard Deviation is value of three independent
experiments
under identical
conditions
Initial dissolved oxygen - 6.91 mg/L and Final disso lved oxygen - 4.64 mg/L
Corrosion
rate Meta l uptake
(mpy )
SD
(pp m)
9.62 0.0 15)
Ferrous =6.76
9.52 0.04
1)
1.48
0.020)
Ferrous =0.071
1.37
0.026)
Cadmium =0.1
Table 6- Mild stee l corrosion reduction
in
Thane creek water by Rh
od r
llia I/lllcilagi ll osa
p
H 9.0)
Sample
Initi al wt of
Final wt
of
IW-FWof
mi ld stee l
mild steel
mild steel
(g) (g) (g)
Mild stee l
co
up on + Thane creek water
samp
le
4.4628
4.4612
0.0016
Mild stee l coupon + Thane creek wate r
5.6804
5.6781
0.0023
sample+ CdCl
:
Mild steel co upon + Thane creek water
6. 1422 6.1414
0.0008
sample+
Rh
od m la Illl1
ci
lag il losa
Mild steel c
oupon
+
Thane
creek water
5.2446
5.2435
0.0011
sample+ CdCI
2
+
Rh od
rllia l1luciiaginosa
SD - The
standard
deviation is va lu e o f three independent experimen ts under identical conditions
Initial di ssolved oxygen - 7. 14 mg/L and Final dissolved oxygen - 6.83 mglL
Corrosion rate
Met a
luptak
(mpy)
SD
(p pm)
4.49
(
0.035)
Ferrous =4.21
5.36 (
0.02)
3.03
0.047)
Ferrous =
O
13
3.26
0.015)
Cadmium =
0.73
Table
7 - Mild steel
co
rro sion reduc
ti
on in
cooling tower
water by
Rhod ru
ia muciiaginosa (pH 7.0)
Sample
Corrosion
rate Ferrous uptake
(mpy)
SD
(pp m)
Mild steel co upon+Thane creek water samp le
12.3(0. 152)
3.77
Mild steel coupon+Thane creek water sample+CdCl
2
12.2(0.208)
3.4
1
Mild st
ee
l co upon+
Than
e creek water
5.84(0.011 ) 1. 124
sa
mple+Rhod rula 1llllc
il
aginoS{J
Mild st
ee
l cOl.lpon+
Tha
'ne creek water sa mpl
e+CdCl
2
+
6.31 (0.025) I I 13
Rh od m/a
lI1ucilagill oslI
SD - The sta n
da
rd deviation is va lue
of
three
independent experiment
s und er id enti
ca
l
cond
itions
Initial di sso lved oxygen - 7.7 mg/L
CdCI : uptake
Dissolved ox yge n
ppm)
(ppm)
0 7.6
29.91 7.7
0 5.3
2.16 6.11
A619. In batch
cultures
, 16 iso lates s
howed corrosion
reduction than the control
17
Scanning
el
ectron
microscopy
showed
the
presence
of cadmium
and ferrous ions in the
cytoplasmic region
of
the
hodotorula ucilaginosa
as observed from Figure 2 The energy dispers ive
x-ray spectroscopy for
cadmium
and ferrou s ion
detection in hodotorula mucilaginosa showed 41.46
per
cent
as
cadmium
as compared to 13.54 per cent as
ferrous .
The e lectrochemical studies showed that the
c
urrent obtained was direc tl
y proportional to the
8/10/2019 JSIR 62(7) 683-689
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688
J SCI INO RES VOL 62 JULY 2003
Figure
1-
I )
Mild
st
ee
l
co
upon in Thane cr
ee
k water,
2)
Mild
s
te
el coupon in Thane cr
ee
k wat er containing
I< hodolOmla IIIf(r
ilag il l
osa ,(3)
Mild
st
ee
l coupon in
cool ing wa ter, 4) Mild st
ee
l Coupon in Coolin g
wa ter containing RIIOr/u/omla IIl/1 cil agillosa
Figure
:2 -
SEM
8/10/2019 JSIR 62(7) 683-689
7/7
DA
BHOL
E
JOISHY
: MILD
STEEL
C
ORROSION RED
UC
TION
IN
WATER
689
Rhodoto rula l11u cilaginosa a lso known to produce
Siderophore) to reduce oxy gen corrosion of mi ld steel
in water may so lve many problems occulTIng 111
cooling towers.
Acknowledgement
Th e authors are grate ful to Dr H S Srinivasan for
carrying out e lec trochemical studi
es
and hi s views on
experim ents.
They
are also thankful to
Dr
C S
Harendranath and Bh arathi Shetye (IlT, Mumbai) for
SEM and EOX anal ys is.
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rt
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