Effects of chitosan inhibitor on the electrochemical corrosion behavior of 2205 duplex stainless steel
Int. J. Miner. Metall. Mater.
Effects of chitosan inhibitor on the electrochemical corrosion behavior of 2205 duplex stainless steel
Se-fei Yang 2
Ying Wen 0 1
Pan Yi 1
Kui Xiao 1
Chao-fang Dong 1
0 Journals Publishing Center, University of Science and Technology Beijing , Beijing 100083 , China
1 Institute for Advanced Materials and Technology, University of Science and Technology Beijing , Beijing 100083 , China
2 Department of Stomatology, General Hospital of the People's Liberation Army , Beijing 100853 , China
The effects of chitosan inhibitor on the corrosion behavior of 2205 duplex stainless steel were studied by electrochemical measurements, immersion tests, and stereology microscopy. The influences of immersion time, temperature, and chitosan concentration on the corrosion inhibition performance of chitosan were investigated. The optimum parameters of water-soluble chitosan on the corrosion inhibition performance of 2205 duplex stainless steel were also determined. The water-soluble chitosan showed excellent corrosion inhibition performance on the 2205 duplex stainless steel. Polarization curves demonstrated that chitosan acted as a mixed-type inhibitor. When the stainless steel specimen was immersed in the 0.2 g/L chitosan solution for 4 h, a dense and uniform adsorption film covered the sample surface and the inhibition efficiency (IE) reached its maximum value. Moreover, temperature was found to strongly influence the corrosion inhibition of chitosan; the inhibition efficiency gradually decreased with increasing temperature. The 2205 duplex stainless steel specimen immersed in 0.4 g/L water-soluble chitosan at 30°C displayed the best corrosion inhibition among the investigated specimens. Moreover, chitosan decreased the corrosion rate of the 2205 duplex stainless steel in an FeCl3 solution.
inhibitor; chitosan; stainless steel; corrosion behavior; electrochemistry
Because of their excellent mechanical properties and
corrosion resistance characteristics [
], the 2205 duplex
stainless steels have been widely applied in numerous fields
in recent years, including the shipbuilding, off-shore oilfield,
chemical, paper and pulp, petrochemical, desalination, and
oil and gas industries [
]. Moreover, because of their high
corrosion resistance and durability, duplex stainless steels
are also attracting increasing interest for use in various
biomedical applications [
]. However, even a small amount
of metal species released from 2205 duplex stainless steel
due to corrosion (electrochemical dissolution or chemical
dissolution) may pose a potential health risk [
Adding a corrosion inhibitor is a simple, low cost, and
adaptable anticorrosion method to improve the corrosion
resistance or stability of 2205 duplex stainless steel. Natural,
low-toxicity, and environmentally friendly corrosion
inhibitors such as chitosan are urgently needed. El-Haddad [
studied the effect and inhibition mechanism of chitosan on
the corrosion behavior of Cu in 0.5 mol/L HCl. Chitosan
was found to essentially act as a mixed-type inhibitor and to
exhibit good inhibition efficiency for Cu in 0.5 mol/L HCl
solution. Moreover, the adsorption of chitosan onto the
specimen surface from solution followed the Langmuir adsorption
isotherm model. Sangeetha et al. [
] reported the corrosion
inhibition performance of synthesized O-fumaryl-chitosan (OFC)
for mild steel in 1 mol/L HCl. Their results suggested that
the inhibition efficiency increased with increasing
concentration of addition inhibitor, reaching a maximum of 94.1%
at 500 × 10−6 OFC. Wang et al. [
] prepared a
chitosan-based low-pH-sensitive intelligent corrosion inhibitor by
loading a pH-sensitive hydrogel with benzotriazole (BTA).
The results from electrochemical tests and immersion
experiments indicated that the intelligent inhibitor provided a
rapid response and effectively inhibited the corrosion of
copper for an extended time period. Fayyad et al. [
prepared an anticorrosion nanocomposite coating that consisted
of chitosan (green matrix), oleic acid, and graphene oxide
(nanofiller). The corrosion resistance of this nanocomposite
coating was compared with that of a pure chitosan coating
by electrochemical impedance spectroscopy (EIS) and
potentiodynamic polarization (PP). El-Mahdy et al. [
synthesized new ionic liquids using chitosan through
amidation and quaternization reactions with oleic acid and
p-toluene sulfonic acid, respectively. The potentiodynamic
polarization data revealed that the prepared ionic liquid
reduced both dissolution and hydrogen evolution corrosion
reactions. EIS was used to elucidate the characteristics of the
charge-transfer process of the steel corrosion. Langmuir
isotherms were found to properly fit the adsorption of the
prepared polymeric ionic liquid over the steel surfaces.
Sangeetha et al. [
] studied the corrosion mitigation of
N-(2-hydroxy-3-trimethyl ammonium) propyl chitosan
chloride (HTACC) as an inhibitor on mild steel. Their
polarization studies revealed that HTACC acted as both an
anodic and a cathodic inhibitor. EIS studies confirmed that
the inhibition occurred through adsorption of HTACC onto
the metal surface. The extent of inhibition exhibited a
negative trend with increasing temperature. However, research
on the corrosion inhibition mechanism of chitosan for
duplex stainless steels has been insufficient.
In the present paper, the effects of chitosan on the
corrosion inhibition behavior of 2205 stainless steel were studied
by electrochemical techniques and immersion tests. A
stereological microscope was used to observe the microstructures of
the duplex stainless steel. Moreover, the optimum parameters
of water-soluble chitosan on the corrosion inhibition
performance of 2205 duplex stainless steel were determined.
The composition of the 2205 duplex stainless steel used
in the experiments is shown in Table 1. To observe the
microstructures of the duplex stainless steel, a specimen was
polished using abrasive silicon carbide papers (400#, 800#,
1200#, and 2000#) and mirror finished with 1-μm polishing
pastes; it was then subjected to ultrasonic cleaning in
alcohol for 5 min and dried in cold air. The polished specimen
was eroded with aqua regia, and the microstructures were
observed by stereology microscopy.
Stainless steel specimens with dimensions of 10 mm × 10
mm × 5 mm were used in electrochemical analyses. Copper
wires were welded to the samples, which were subsequently
embedded in epoxy resin. Before the electrochemical tests, all
the specimens were subjected to polishing and mirror finishing.
Electrochemical tests were performed in a conventional
three-electrode system using a model VMP3
electrochemical system (EG&G Princeton Applied Research). A Pt plate
and a saturated calomel electrode were used as the counter
electrode and the reference electrode, respectively. Polarization
measurements were conducted from −0.5 V vs. open-circuit
potential toward the anodic direction; the scan rate was 0.1667
mV/s. All electrochemical tests were conducted under a
constant controlled temperature in a thermostated water-bath
cauldron. The electrolytes used in the electrochemical
measurements were 3.5wt% NaCl solutions, which were prepared from
analytical-grade reagent and deionized water.
To observe the morphology of pits, the specimens were first
cleaned with deionized water and dried with cold air after the
polarization tests. The specimens were then treated with erosion
solution and again cleaned with alcohol and deionized water.
2.3. Immersion tests
As is well known, 2205 duplex stainless steel exhibits
good corrosion resistance but suffers from pitting corrosion
in specific environmental media under certain temperature
and pH conditions [
]. In the present work, to further
characterize the corrosion inhibition performance of
chitosan for 2205 duplex stainless steel, immersion tests in FeCl3
were performed in accordance with standard GB/T
10125–1997; carboxylated chitosan ((C6H11NO4)n) was used.
The specimens, whose dimensions were 25 mm × 50 mm ×
2 mm, were polished according to standard GB/T248.1. The
immersion test specimens were divided into two groups:
group-A specimens were immersed in 6wt% FeCl3 solution;
group-B specimens were immersed in 6wt% FeCl3 + 0.2 g/L
chitosan solution. To determine the mass loss, the specimens
were subsequently subjected to chemical etching according
to standard GB/T 16545–1996 and were then cleaned with
alcohol and deionized water. Before and after the immersion
tests, the specimens were weighed on the same balance. The
using the EC-Lab software; the fitted results are shown in
Table 2. The inhibition efficiency (IE) was calculated as
IE = 1 − icorr ×100% (1)
where icorr represents the corrosion current density of
specimens exposed in chitosan solution for different times (2, 4, 6,
and 8 h) and i0 is the corrosion current density of the blank
specimen (0 h).
The results in Fig. 2 and Table 2 indicate that Ecorr slightly
decreases with increasing immersion time in the chitosan
solution. This behavior is mainly due to the complex
reaction between the reactive functional groups of chitosan and
metal ions in solution. Usually, a compact adsorption film
will form on and cover the surface of a steel specimen
through Langmuir adsorption [
]. However, in the
present case, the complex reaction suppresses the formation
of an adsorption film on the surface. The absolute value of
the cathodic Tafel slope of the polarization curves (βc)
changes only slightly as a function of immersion time; by
contrast, the value of the anodic Tafel slope of the polarization
curves (βa) first decreases and then increases with increasing
immersion time, which indicates that the chitosan acts as a
mixed-type inhibitor for 2205 duplex stainless steel in 3.5wt%
NaCl solution. Previously published results [
] also show
that chitosan is a mixed-type inhibitor for carbon steel.
micromorphology of the specimens after the immersion tests
was observed by scanning electron microscopy (SEM, FEI
3. Results and discussion
Fig. 1 shows the microstructures of the 2205 duplex
stainless steel. It mainly consists of ferrite and austenite
phases, where the striped black parts are austenite and the
white parts are the ferrite matrix. The calculation results of
the two phase contents (area fraction) analyzed using the
ImageTool software show that the microstructures are composed
of 48.6% ferrite phase and 51.4% austenite, which satisfies the
requirements specified in standard ASTM A240/A240M–01.
To characterize the corrosion inhibition of water-soluble
chitosan for 2205 duplex stainless steel, immersion tests
were carried out. In these experiments, the specimens were
immersed in a 0.2 g/L water-soluble chitosan solution for
various times and subsequently subjected to a polarization
test in 3.5wt% NaCl solution. The polarization results for
the specimens exposed to water-soluble chitosan for various
times are shown in Fig. 2. The inset of Fig. 2 is an enlarged
view of the red-boxed area. To obtain the parameters related
to the corrosion process, the polarization curves were fitted
Compared with the blank specimen (0 h), the specimens
with chitosan inhibitor exhibit a smaller corrosion current
density, a greater pitting potential, and a wider anodic
passivation zone, which demonstrates the excellent inhibition
effect of chitosan on 2205 stainless steel. Moreover, the IE
progressively increases with increasing immersion time in
the 0.2 g/L chitosan solution. However, when the immersion
time is longer than 4 h, the IE decreases. This behavior is
attributable to damage to the adsorption film created by the
complex reaction between the reactive groups of chitosan
and metal ions.
After the polarization tests, the morphologies of pits on
the specimens’ surfaces were observed, as shown in Fig. 3.
A large number of small pitting sites exist at the junctures of
the two phases. However, the number of pits is substantially
lower on the surfaces of specimens previously immersed in
0.2 g/L chitosan solution for 2 h. This result further
demonstrates the outstanding corrosion inhibition by the chitosan
inhibitor for the 2205 duplex stainless steel.
3.3. Effects of temperature on corrosion inhibition performance
Fig. 4 shows the polarization curves of 2205 duplex
stainless steel at different temperatures in 3.5wt% NaCl
solution. The small plots in Fig. 4 are the polarization curves
of specimens immersed for 2 h in 0.2 g/L chitosan solution
at different temperatures. All of the curves show the same
behavior, which indicates that the electrochemical reaction
mechanism under different temperature conditions is the
same. That is, the anodic process is the dissolution reaction
of the metal electrode and the cathode reaction is the
depolarization process of oxygen. Moreover, the corrosion
current density gradually increases and the corrosion potential
decreases with increasing temperature.
The polarization curves in Fig. 4 were fitted; the results
are shown in Table 3. The chitosan exhibits the best
corrosion inhibition efficiency at 30°C. Under other temperature
conditions, the chitosan still inhibits corrosion of the 2205
duplex stainless steel but the IE value gradually decreases
with increasing temperature. Because of the higher kinetic
energy of molecules at higher temperatures, adsorption is
difficult; the desorption effect of the corrosion inhibitor is
enhanced at higher temperatures, which affects the
formation of the stable and compact film layer. A comparison of
the polarization curve of the specimen immersed for 2 h
with that of the blank specimen (0 h) reveals that parameters
βa and βc change. Thus, the chitosan solution still exhibits a
mixed-type inhibition behavior at different temperatures.
Fig. 5 shows the polarization curves of the specimens
immersed for 2 h at 30°C in chitosan solutions with various
concentrations. The corresponding fitted results are
displayed in Table 4. With increasing chitosan concentration,
Ecorr shifts toward more negative potentials and Ep increases
slightly. The Ep reaches its maximum value when the
chitosan concentration is 0.4 g/L. Moreover, βa reaches its
maximum value at 0.8 g/L. This result implies that a high
concentration of chitosan is beneficial to rapid adsorption onto
the specimen surface and to the formation of a uniform and
dense inhibition film. However, with increasing
concentration, the complex reaction that occurs between the reactive
groups of chitosan molecules and metal ions generated in
the corrosion process is enhanced, which reduces the
inhibition efficiency. Given the aforementioned results, the best
corrosion inhibition performance is attained at a chitosan
concentration of 0.4 g/L.
3.5. Immersion tests
Fig. 6 displays the corrosion rates of specimens in the
immersion tests. The corrosion rates of the group-A
specimens (6wt% FeCl3) are consistently higher than those of
the group-B specimens (6wt% FeCl3 + 0.2 g/L chitosan
solution), which implies that chitosan slows the corrosion rate
of the 2205 duplex stainless steel. Moreover, the corrosion
rates of the group-B specimens tend to decrease in the early
stages of the experiment but increase after the specimens
have been immersed for 96 h. This behavior is attributed to
the formation of a dense adsorption film onto the specimen
surface at the initial stage, which may suppress the corrosion
process of the specimens. However, with increasing
immersion time, the adsorption film is also damaged by Cl−. Thus,
the corrosion rate tends to increase at the end of the
experiment. In this situation, pitting corrosion may occur on the
specimen surface. To investigate this possibility, we
observed the micromorphology of the specimens immersed for
120 h, and the results are shown in Fig. 7. Numerous pits are
scattered on the surface of the group-A specimen, which
demonstrates that the specimen immersed in FeCl3 solution
suffers from serious corrosion. The pit diameter is almost 10
μm. However, in the case of the surface of the group-B
specimen, only slight corrosion is observed. Moreover, the pits
are relatively small and few in number. These results
suggest that the chitosan exhibits excellent corrosion inhibition
performance on the 2205 duplex stainless steel.
(1) In the 3.5wt% NaCl solution system, the
water-soluble chitosan exhibited excellent corrosion
inhibition performance for 2205 duplex stainless steel.
Polarization curves suggest that chitosan acted as a mixed-type
inhibitor. When the specimen was immersed in 0.2 g/L
chitosan solution for 4 h, a dense and uniform adsorption film
covered the sample surface and the IE reached its
(2) Temperature strongly influences the corrosion
inhibition of chitosan. The 2205 duplex stainless steel specimen
immersed in 0.4 g/L water-soluble chitosan at 30°C displays
the best corrosion inhibition. Moreover, chitosan can also
decrease the corrosion rate of 2205 duplex stainless steel in
This work was financially supported by the National
Natural Science Foundation of China (No. 81371183).
Open Access This article is distributed under the terms of
the Creative Commons Attribution 4.0 International License
permits unrestricted use, distribution, and reproduction in any
medium, provided you give appropriate credit to the original
author(s) and the source, provide a link to the Creative
Commons license, and indicate if changes were made.
 J. Verma and R.V. Taiwade , Effect of welding processes and conditions on the microstructure, mechanical properties and corrosion resistance of duplex stainless steel weldments-A review , J. Manuf. Processes , 25 ( 2017 ), p. 134 .
 A. Momeni , S. Kazemi , and A. Bahrani , Hot deformation behavior of microstructural constituents in a duplex stainless steel during high-temperature straining , Int. J. Miner. Metall. Mater. , 20 ( 2013 ), No. 10 , p. 953 .
 X.Q. Cheng , C.T. Li , C.F. Dong , and X.G. Li , Constituent phases of the passive film formed on 2205 stainless steel by dynamic electrochemical impedance spectroscopy , Int. J. Miner. Metall. Mater. , 18 ( 2011 ), No. 1 , p. 42 .
 A.V. Jebaraj , L. Ajaykumar , C.R. Deepak , and K.V.V. Aditya , Weldability, machinability and surfacing of commercial duplex stainless steel AISI2205 for marine applications-A recent review , J. Adv. Res. , 8 ( 2017 ), No. 3 , p. 183 .
 J. Charles , Duplex stainless steels-a review after DSS'07 in Grado , Steel Res. Int. , 79 ( 2008 ), No. 6 , p. 455 .
 M. Lundin , Y. Hedberg , T. Jiang , G. Herting , X. Wang , E. Thormann , E. Blomberg, and I.O. Wallinder , Adsorption and protein-induced metal release from chromium metal and stainless steel , Adv. Colloid Interface Sci ., 366 ( 2012 ), No. 1 , p. 155 .
 M. Conradi , P.M. Schön , A. Kocijan , M. Jenko , and G.J. Vancso , Surface analysis of localized corrosion of austenitic 316L and duplex 2205 stainless steels in simulated body solutions , Mater. Chem. Phys. , 130 ( 2011 ), No. 1-2 , p. 708 .
 J.S. Liu , Q. Wang , C. Lv , J.N. Sun , Z.Q. Chen , and N. Gao , Elemental release from Ni-Cr dental alloy in artificial saliva and saline solution , Mater. Sci. Forum , 610 - 613 ( 2009 ), p. 1164 .
 M.N. El-Haddad , Chitosan as a green inhibitor for copper corrosion in acidic medium , Int. J. Biol. Macromol ., 55 ( 2013 ), No. 2 , p. 142 .
 Y. Sangeetha , S. Meenakshi , and C.S. Sairam , Interactions at the mild steel acid solution interface in the presence of O-fumaryl-chitosan: Electrochemical and surface studies , Carbohydr . Polym., 136 ( 2016 ), p. 38 .
 Y.N. Wang , C.F. Dong , D.W. Zhang , P.P. Ren , L. Li , and X.G. Li , Preparation and characterization of a chitosan-based low-pH-sensitive intelligent corrosion inhibitor , Int. J. Miner. Metall. Mater. , 22 ( 2015 ), No. 9 , p. 998 .
 E.M. Fayyad , K.K. Sadasivuni , D. Ponnamma , and M.A. Almaadeed , Oleic acid-grafted chitosan/graphene oxide composite coating for corrosion protection of carbon steel, Carbohydr . Polym., 151 ( 2016 ), p. 871 .
 G.A. El-Mahdy , A.M. Atta , H.A. Al-Lohedan , and A.O. Ezzat , Influence of green corrosion inhibitor based on chitosan ionic liquid on the steel corrodibility in chloride solution , Int. J. Electrochem. Sci. , 10 ( 2015 ), No. 7 , p. 5812 .
 Y. Sangeetha , S. Meenakshi , and C. Sairamsundaram , Corrosion mitigation of N-(2-hydroxy-3-trimethyl ammonium)propyl chitosan chloride as inhibitor on mild steel , Int. J. Biol. Macromol ., 72 ( 2014 ), p. 1244 .
 M. Hoseinpoor , M. Momeni , M.H. Moayed , and A. Davoodi , EIS assessment of critical pitting temperature of 2205 duplex stainless steel in acidified ferric chloride solution, Corros . Sci., 80 ( 2014 ), No. 3 , p. 197 .
 M. Gholami , M. Hoseinpoor , and M.H. Moayed , A statistical study on the effect of annealing temperature on pitting corrosion resistance of 2205 duplex stainless steel, Corros . Sci., 94 ( 2015 ), p. 156 .
 S.A. Umoren , M.M. Solomon , I.I. Udosoro , and A.P. Udoh , Synergistic and antagonistic effects between halide ions and carboxymethyl cellulose for the corrosion inhibition of mild steel in sulphuric acid solution , Cellulose , 17 ( 2010 ), No. 3 , p. 635 .
 S. Cheng, S.G. Chen, T. Liu , X.T. Chang , and Y.S. Yin , Carboxymenthylchitosan as an ecofriendly inhibitor for mild steel in 1M HCl, Mater . Lett., 61 ( 2007 ), No. 14 - 15 , p. 3276 .
 S.A. Umoren , M.J. Banera , T. Alonso-Garcia , C.A. Gervasi , and M.V. Mirífico , Inhibition of mild steel corrosion in HCl solution using chitosan , Cellulose , 20 ( 2013 ), No. 5 , p. 2529 .
 Y. Liu , C.J. Zou , X.L. Yan , R.J. Xiao , T.Y. Wang , and M. Li , β-cyclodextrin modified natural chitosan as a green inhibitor for carbon steel in acid solutions , Ind. Eng. Chem. Res. , 54 ( 2015 ), No. 21 , p. 5664 .