Journal of Minerals and Materials Characterization and Engineering, 2012, 11, 836-840
Published Online August 2012 (
Comparative Assessment of Corrosion Behaviour of MCS
and KS7 SS in Saline and Carbonate Environments
Olusegun Olufemi Ajide*, Kamorudeen Wemimo Agara
Department of Mechanical Engineering, University of Ibadan, Ibadan, Nigeria
Email: *
Received June 8, 2012; revised July 19, 2012; accepted August 10, 2012
The major objective of this experimental study is to investigate and compare the corrosion resistance of medium Carbon
steel (MCS) and KS7 stainless steel in saline and sodium carbonate environments. The MCS and KS7 SS were exposed
to 0.5 M each of NaCl and Na2CO3 solutions for a period of 36 days. The weight loss was taken every 3 days in order to
evaluate CPR. The results obtained showed that KS7 SS generally offers a better corrosion resistance than the MCS in
the selected media. While MCS is found to be inappropriate alloy in saline and sodium carbonate environments, KS7
SS is an unfailing choice material for manufacturing machines and other engineering amenities in which their service
lives are predominant in Na2CO3 medium and fairly pleasing in NaCl environment.
Keywords: MCS; KS7 SS; CPR; Saline and Sodium Carbonate
1. Introduction
The challenges of corrosion in manufacturing and do-
mestic sectors are enormous. Corrosion is the major
problem facing exploration, production and processing in
oil and gas, food and construction industries. It is therefore
germane to concentrate efforts and resources towards
meaningful researches that will be a relief to the numer-
ous harms of corrosion in industries. [1] studied the Cor-
rosion behaviour of dc magnetron sputtered Fe1xMgx
alloy films in 3 wt% NaCl solution. Fe1xMgx alloy films
(with x 43.4 at % Mg) were deposited by dc magnetron
sputtering onto glass slide substrates. The aim of their
work was to characterize the corrosion properties of
these alloys in saline solution for application as new
friendly environmentally sacrificial coatings in the pro-
tection of steel structures. The morphological and struc-
tural properties of the alloys were systematically studied
prior to electrochemical experiments, and then the de-
graded surfaces were analyzed to determine the composi-
tion and nature of corrosion products. The reactivity of
the alloys in saline solution is strongly dependent on the
Mg content and the alloy structure. A transition in corro-
sion activity is observed at 25% Mg from which the reac-
tivity decreases with the magnesium content increase.
From this paper, it is evident that an increase in % Mg
decreases the corrosion rates of this alloy. [2] presented a
paper on corrosion assessment of offshore oil pipeline
based on ultrasonic technique. He developed an intelli-
gent ultrasonic inspection device for offshore pipeline
inspection and software for corrosion assessment of off-
shore pipeline. [3] in 2009 work studied the comparative
corrosion behaviour of Al 3103 and galvanized steel
roofing sheets in 1 M, 0.5 M and 0.3 M solutions of so-
dium carbonate and sodium chloride. Samples of the
aluminium and galvanized sheets were subjected to the
different environments for thirty days. The electrode po-
tentials, in mV (SCE), were measured every day. Elec-
trode potential measurements were taken every day for
thirty consecutive days. Weight loss or gain measure-
ments were taken every three days for the duration of the
exposure period. The results of their study showed that
sodium chloride environment had higher corrosive effect
on the galvanized roofing sheet than sodium carbonate
environment while the reverse was true for aluminium
sheets. Also, galvanized steel roofing corroded more than
aluminium roofing in both carbonate and chloride envi-
ronments. Corrosion of galvanized steel roofing was con-
tinuous throughout the exposure period in all the envi-
ronments used. The conclusions drawn by the authors is
that galvanized steel roofing sheet is not a suitable mate-
rial for roofing in carbonate and chloride environments
or in industrial environments where chloride or carbonate
contamination is possible. [4] evaluated the corrosion
behaviour of carbon steel under stagnant seawater condi-
tions. 1020 carbon steel coupons were subjected to natu-
ral seawater for a 1-year period. The study showed that
this alloy is more corrosive in anaerobic stagnant sea-
water conditions than aerobic conditions. The study also
*Corresponding author.
Copyright © 2012 SciRes. JMMCE
O. O. AJIDE, K. W. AGARA 837
revealed that in both aerobic and anaerobic exposures,
corrosion was more aggressive on horizontally oriented
coupons compared to vertically oriented samples. The
corrosion behaviour of low carbon steel was investigated
in natural seawater and various synthetic seawaters as
reported by [5] in 2006. It was found that the steel cor-
roded nearly four times faster in a 3.5% NaCl solution
than in natural seawater for an exposure time of 21 days.
The corrosion rate after immersion in synthetic seawaters
(ASTM D1141 and Marine Biological Laboratory sea-
water) is similar to the corrosion rate after immersion in
natural seawater. Calcium carbonate (aragonite) deposits
were found on the surface of the steel after immersion in
natural seawater and the synthetic seawaters. Some
magnesium-containing deposits were also found after
immersion in the natural seawater. These deposits act as
a barrier against oxygen diffusion and thereby lower the
corrosion rate. The morphology of the calcium carbonate
deposits that formed during immersion in the natural
seawater is different from those formed during immer-
sion in the solution. [6] studied the electrochemical cor-
rosion behaviour of carbon steel X60 using the electro-
chemical impedance spectroscopy and potentiodynamic
polarization methods. 0.5 M test solutions of sodium
chloride, sodium sulphate and sulphuric acid were used
in a three electrode open cell. The findings of the authors
showed that the rate of corrosion penetration is higher for
carbon steel X60 in 0.5 M sulphuric acid and smaller in
0.5 M sodium sulphate. [7] studied the corrosion behav-
iour of steel for snow and rockfall barriers using electro-
chemical techniques to quantify corrosion rate. His re-
sults generally showed that steels have high corrosion
rate in these media. Synthetic seawaters. This may ex-
plain the slightly lower corrosion rates obtained in the
natural seawater. X-ray diffraction also showed that the
oxy-hydroxides formed in the 3.5% NaCl solution dif-
fered from those formed in the other solutions. [8] inves-
tigated the corrosion behaviour of carbon steel in alkaline
medium in the presence of very low concentration of
polymeric nanoaggregates (0.0024 wt% polyethylene
oxide-PEO-113-b-PS70 micelles). The steel electrodes
were investigated in chloride-free and chloride-contain-
ing cement extracts. The electrochemical measurements,
electrochemical impedance spectroscopy and potentio-
dynamic polarization indicate that the presence of mi-
celles alters the composition of the surface layer and in-
fluences the electrochemical behaviour of the steel. Au-
thors’ observation shows that micelles initially improved
the corrosion resistance of the steel whereas no signifi-
cant improvement was observed within longer immersion
periods. Surface analysis, performed by environmental
scanning electronic microscopy, energy-dispersive X-ray
analysis and X-ray photoelectron spectroscopy supports
and elucidates the corrosion performance characteristics
of carbon steel in simulated pore solution in the presence
of Micelles. [9] in 2011 did a comparative study of cor-
rosion resistance between 316 and different duplex
stainless steel grades. He examined and compared the
corrosion properties of 316L austenitic stainless steel and
duplex grades of LDX2101, SAF2304, AL2003, LDX-
2404, 2505 and 2507.The stainless steels were given heat
treatment at temperature of 800˚C for 30 minutes. Influence
of heat treatment on pitting susceptibility of stainless
steels was estimated using cyclic polarization scan which
is based on ASTM standard G150. Metallurgical analysis
was conducted to find a correlation between microstruc-
ture and pitting resistance. Light microscope was used
for the examination of stainless steel microstructure. In
addition, test samples were examined virtually after pit-
ting tests and critical pitting test to determine the corro-
sion form which was present. The results of his research
showed that pitting corrosion resistance and critical pit-
ting temperature (CPT) values of heat treated highly al-
loyed steels were affected adversely compared with the
results from non-heat treated materials. The author af-
firmed that for stainless steel alloys, the results can be
attributed to metallurgical aspects such as sigma, chro-
mium nitrides, secondary austenite and etc. The author
concluded that the precipitations have significant effects
on corrosion behaviour in stainless steel alloys. [10] in-
vestigated the influence of CO2 on the corrosion behav-
iour of 13Cr martensitic stainless steel AISI 420 and
low-alloyed steel AISI 4140 exposed to saline aquifer
water environment. In order to guarantee the safety of the
site, CO2-corrosion of the injection pipe steels has to be
given special attention. To get to know the corrosion
behaviour samples of the heat treated steel AISI 4140,
42CrMo4, used for casing, and the martensitic stainless
injection pipe steel AISI 420, X46Cr13 were kept at T =
60˚C and p = 1 - 60 bar for 700 h - 8000 h in a CO2-satu-
rated synthetic aquifer environment similar to the geo-
logical CCS-site at Ketzin, Germany .The isothermal
corrosion behaviour obtained by mass gain of the steels
in the gas phase, the liquid phase and the intermediate
phase gives surface corrosion rates around 0.1 to 0.8
mm/year. This implies that Severe pit corrosion with pit
heights around 4.5 mm are only located on the AISI 420
steel. Main phase of the continuous complicated multi-
layered carbonate/oxide structure is siderite FeCO3 in
both types of steel. The corrosion of 18-8 stainless steel
in sodium chloride solutions was studied by [11]. It was
established that under certain conditions, 18-8 stainless
steel is likely to fail in contact with sodium chloride so-
lutions through formation of deep pits. 200 series
stainless steel is currently of great interest to material
researchers, engineers and steel vendors due to its dis-
tinctive mechanical characteristics and acceptable corro-
sion behaviour. According to [12], new grades of the 200
Copyright © 2012 SciRes. JMMCE
Copyright © 2012 SciRes. JMMCE
series have been uncovered for the European market. It is
a potential substitute to austenitic grade AISI 304. It has
low nickel content without compromising its austenite
phase former characteristic. A cautious comparison of
the experimental data of the new 200 series and the ex-
isting 300 and 400 series stainless steels were made. This
article revealed that the new 200 grades have mechanical
properties slightly superior to AISI 304 combined with
satisfactory corrosion resistance behaviour.
pons surfaces were treated by abrading them through
successive grades of silicon carbide papers of grades 60
and 120 grit, and finally on the 0.05 μm emery cloth grade.
They were rinsed in distilled water and then in acetone
and later dried. The prepared coupons were stored in
desiccators until when used for the experiments. After
three days of storage; the coupons were immersed in
each 0.5 M, 100 ml of NaCl and Na2CO3 Solutions for a
period of 36 days. The corrosion coupons were removed
from the corrosion media with the aid of a tong. These
were then properly cleaned in distilled water and dried
with cotton wool. The dried samples were weighed with
the electronic digital weighing balance and recorded.
Weight loss measurements of coupons were recorded at
interval of 3 days. The corrosion penetration rate (CPR)
were evaluated from the weight loss measurements using
the Equation (1):
2. Materials and Methods
2.1. Chemical Analysis
The MCS was procured from the universal steel Limited,
Ikeja, Lagos state while KS7 SS was bought from a
stainless steel commercial dealer in Nigeria. KS7 SS is
one of the 200 series stainless steels produced by KAD
Steel Rolling Mills in India. The chemical Composition
Analysis of Medium Carbon steel (MCS) and KS7
Stainless steel that was carried out at the Universal steel
Limited, Lagos state in Nigeria are shown in Tables 1
and 2 respectively.
2.2. Weight Loss Measurements
The MCS and KS7 SS samples were machined into cy-
lindrical and rectangular coupons of 15 mm diameter and
41 mm long and 44 mm by 45 mm respectively. The cou-
CPR (1)
where K = constant = 3.45 × 106;
CPR = Corrosion Penetration Rate in mils per
year (mpy);
W = the weight loss in grams;
A = Area of exposed specimen in cm2;
t = time or duration of exposure in hours;
ρ = Density of material in g/cm3.
Table 1. Chemical composition analysis of medium carbon steel (MCS).
Run C Si S P Mn Ni Cr
1 0.3397 0.2191 0.0573 0.0620 0.8294 0.0960 0.1242
2 0.3426 0.2204 0.0605 0.0597 0.8343 0.0961 0.1245
Avg 0.3411 0.2198 0.0589 0.0609 0.8318 0.0960 0.1244
Mo V Cu W As Sn Co Al Pb Ca Zn Fe%
0.0188 0.0057 0.2066 0.0035 0.0056 0.0252 0.0088 –0.00070.0001 0.0001 0.0035 97.9951
0.0191 0.0058 0.2077 0.0035 0.0059 0.0262 0.0088 –0.0007–0.00000.0001 0.0038 97.9816
0.0189 0.0058 0.2071 0.0035 0.0058 0.0257 0.0088 –0.00070.0001 0.0001 0.0036 97.9883
Table 2. Chemical composition analysis of KS7 stainless steel.
Run C Si S P Mn Ni Cr
1 0.1099 9.3663 0.0150 0.0640 10.0512 0.3414 11.4664
2 0.1105 0.3534 0.0187 0.0728 10.6255 0.3532 11.1139
Avg 0.1102 0.3598 0.0169 0.0684 10.7384 0.3473 11.292
Mo V Cu W As Sn Co Al Pb Ca Zn Fe%
–0.3414 0.0748 4.6323 0.0817 0.0246 0.0219 0.0444 0.0146 0.0236 0.0004 0.0340 71.8657
–0.0291 0.0731 4.0527 0.0800 0.0242 0.0229 0.0450 0.0121 0.0206 0.0003 0.0326 73.0176
–0.0306 0.739 4.3425 0.0808 0.0244 0.0224 0.0447 0.0134 0.0221 0.0003 0.0333 72.4417
O. O. AJIDE, K. W. AGARA 839
3. Results and Discussion
3.1. Results
See Tables 1 and 2 and Figures 1 and 2.
3.2. Discussion
The corrosion characteristics of MCS and KS7 SS in 0.5
M, 100 ml Nacl solution is shown in Figure 1. MCS re-
sumed the corrosion deterioration on the 6th day with
CPR of 4.2 mpy and this trend continued throughout the
36 days of experimentation. It has the highest corrosion
degradation between the 12th and 15th days with CPR of
7.8 mpy and 6.3 mpy. Whereas, KS7 SS experienced an
approximate no corrosion deterioration within the first 9
days. A significant corrosion penetration was experi-
enced between the 12th and 18th days as a result of sud-
den decrease of solution pH from 6.9 to 3.2, 2.3 and 2.2
on the 12th, 15th and 18th days respectively. The CPR
recorded in these days is respectively 5.8 mpy, 5.6 mpy
and 4.1 mpy. With increase in pH to 4.7 on the 21st day,
there was a remarkably decrease to an approximate 0.0
mpy. This approximate no corrosion continued through-
out the remaining period of 36 days experimentation. The
formation of chromium oxide which acted as protective
layer was responsible for this high passiveness to corro-
sion degradation of KS7 SS in this latter period. Com-
paratively, KS7 SS has moderate but better corrosion
properties than MCS in saline medium. In similar manner,
Figure 2 gives a description of the corrosion behaviour
of MCS and KS7 SS in 0.5 M, 100 ml Na2CO3 solution.
MCS resumed corrosion degradation on the 6th day with
CPR of 2.3 mpy. An inconsistent corrosion penetration
was experienced from the 9th day till the 21st day with
peak value of 5.3 mpy. However, a daily gradual decrease
of CPR began on the 24th day with CPR of 0.3 mpy.
Between 33rd and 36th days, an approximate no corro-
sion deterioration was experienced. The formation of
passive film at the latter part of experimentation was re-
sponsible for this unusual decrease in corrosion deterio-
ration behaviour. Apart from the first 3 days when a CPR
of 4.4 mpy was experienced, KS7 SS exhibited a very
high corrosion resistance characteristic with an approxi-
mate CPR of 0.0 mpy throughout the 36 days. A protec-
tive barrier of Chromium oxide which was formed at the
6th day is undoubtedly the cause of KS7 SS corrosion
passiveness in this carbonate environment. Observably,
KS7 SS has exhibited a more reliable potential for corro-
sion resistance ability in sodium carbonate medium com-
pared to MCS.
4. Conclusions
It is obvious from these experiments to draw the follow-
ing conclusions:
Figure 1. CPR of MCS and KS7 SS in NaCl solution.
Figure 2. CPR of MCS and KS7 SS in Na2CO3.
1) Due to very high corrosion degradation characteris-
tics of MCS, it is considered undependable and inappro-
priate alloy in the fabrication of equipments and tools for
processing Salts and sodium carbonate (or where they
exist as contaminants).
2) KS7 SS possess distinct corrosion resistance char-
acteristics compared to MCS and consequently highly
unfailing and acceptable alloy material for producing
machinery, accessories, tanks , pipes and other engineer-
ing facilities meant to perform in sodium carbonate me-
dium and moderately satisfactory in salty environment.
[1] C. Berziou, K. Remy, A. Billard and J. Creus, “Corrosion
Behaviour of dc Magnetron Sputtered Fe1xMgx Alloy
Films in 3 wt% NaCl Solution,” Corrosion Science, Vol.
49, No. 11, 2007, pp. 4276-4295.
[2] Q. I. Zhang, “Corrosion Assessment of Offshore Oil Pipe-
line Based on Ultrasonic Technique,” Shanghai Jiao Tong
University, Shanghai, 2008.
[3] D. T. Oloruntoba, O. O. Oluwole and O. Oguntade, “Com-
Copyright © 2012 SciRes. JMMCE
parative Study of Corrosion Behaviour of Galvanized
Steel and Coated Al 3103 Roofing Sheets in Carbonate
and Chloride Environments,” Materials & Design, Vol.
30, No. 4, 2009, pp. 1371-1376.
[4] S. L. Jason, I. R. Richard, J. L. Edward, U. F. Alexander
and J. L. Brenda, “An Evaluation of Carbon Steel Corro-
sion under Stagnant Seawater Conditions,” Biofouling:
The Journal of Bioadhesion and Biofilm Research, Vol.
20, No. 4-5, 2004, pp. 237-247.
[5] H. Möller, E. T. Boshoff and H. Froneman, “The Corro-
sion Behaviour of a Low Carbon Steel in Natural and
Synthetic Seawaters,” The Journal of The South African
Institute of Mining and Metallurgy, Vol. 106, 2006, pp.
[6] A. C. Ciubotariu, L. Benea and P. L. Bonora, “Corrosion
Studies of Carbon Steel X60 by Electrochemical Meth-
ods,” Journal of Optoelectronics and Advanced Materials,
Vol. 12, No. 5, 2010, pp. 1170-1175.
[7] F. Deflorian, S. Rossi, B. Tancon and P. L. Bonora, “Cor-
rosion Behaviour of Steel Ropes for Snow and Rockfall
Barriers,” Corrosion Engineering, Science and Technol-
ogy, Vol. 39, No. 3, 2004, pp. 250-254.
[8] J. Hu, D. A. Koleva, J. H. W. de Wit, H. Kolev and K.
van Breugel, “Corrosion Performance of Carbon Steel in
Simulated Pore Solution in the Presence of Micelles,”
Journal of the Electrochemical Society, Vol. 158, No. 3,
2011, pp. C76-C87.
[9] G. Elnura, “Comparison of Corrosion Resistance of 316
and Different Stainless Steel Grades,” Master Thesis, Uni-
versity of Stavanger, Stavanger, 2011.
[10] A. Pfennig and A. Kranzmann, “Influence of CO2 on the
Corrosion Behaviour of 13Cr Martensitic Stainless Steel
AISI 420 and Low-Alloyed Steel AISI 4140 Exposed to
Saline Aquifer Water Environment,” Transactions of the
Wessex Institute, 2006, 10 p.
[11] H. H. Uhlig and M. C. Morill, “Corrosion of 18-8
Stainless Steel in Sodium Chloride Solutions,” Industrial
& Engineering Chemistry, Vol. 33, No. 7, 1941, pp. 875-
[12] J. Charles, J. D. Mithieux, J. Krautschick, N. Suutala, S. J.
Antonio, S. Van Hecke and T. Pauly, “A New European
200 Series Standard to Substitute 304 Austenitics?” Re-
vue de Métallurgie, Vol. 106, No. 2, 2009, pp. 90-98.
Copyright © 2012 SciRes. JMMCE