Volume 20 Preprint 32
STREPTOMYCES KANAMYCETICUS DERIVATIVE: AN EXCELLENT CORROSION INHIBITOR
E.L.Harish and S.Karthikeyan
Keywords: Mild Steel; Corrosion Inhibition; Kanamycin A; Adsorption Isotherm; Green inhibitor
Corrosion inhibition of mild steel in 1M Sulphuric acid with an anti-bacterial agent, viz., Streptomyces kanamyceticus derivative, Kanamycin A as corrosion inhibitor has been studied by using mass loss, potentiodynamic polarization, electrochemical impedance spectroscopy and hydrogen permeation studies. All these techniques reveal that inhibition efficiency increases with the increase in the concentration of antibacterial agent. Polarization studies indicated that inhibitor acted as cathodic inhibitor. It was found that the adsorption of green inhibitor on the mild steel surface obeying Langmuir adsorption isotherm.
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DERIVATIVE: AN EXCELLENT CORROSION
E.L.Harisha and S.Karthikeyanb*
School of civil and chemical engineering, VIT University, Vellore, Tamilnadu, India.
Centre for Innovative Manufacturing Research, VIT University, Vellore, Tamilnadu,
(*Corresponding author, firstname.lastname@example.org)
of mild steel in 1M Sulphuric acid with an anti-bacterial
agent, viz., Streptomyces kanamyceticus derivative, Kanamycin A
inhibitor has been studied by using
mass loss, potentiodynamic
electrochemical impedance spectroscopy and hydrogen permeation studies. All these
techniques reveal that inhibition efficiency increases with the increase in the
concentration of antibacterial agent. Polarization studies indicated that inhibitor acted
as cathodic inhibitor. It was found that the adsorption of green inhibitor on the mild
steel surface obeying Langmuir adsorption isotherm.
Keywords: Mild Steel; Corrosion Inhibition; Kanamycin A; Adsorption Isotherm; Green
Mild steel is an important class of metals due to its outstanding mechanical
properties. It is widely used under different conditions in chemical and allied industries
in handling acidic, alkaline and salt solutions. Mild steel is used in industries as
pipelines for petroleum industries, storage tanks, reaction vessel and chemical
batteries . Acid solutions are widely used in many industrial processes like acid
cleaning, pickling and descaling due to their chemical properties [2-5]. Acids cause
damage to the steel substrate, because of their corrosive nature. Several methods were
used to reduce
the corrosion of metals in acidic medium, but the use of inhibitors is
most widely employed [6-10].
Organic compounds are widely used as corrosion inhibitors for mild steel in
acidic media [11-16].
The rate of corrosion retards by adsorption of organic
inhibitors on the mild steel surface. The inhibitors block the reactive parts by replacing
water molecules and form a dense barrier layer on the metal surface. The majority of
the organic inhibitors are toxic, highly expensive and non environment friendly.
Research activities in recent times are booming on developing the cheap, non-toxic
drugs as environment friendly corrosion inhibitors [17-21].
The aim of this study is to examine the corrosion protection efficacy of
Kanamycin A for mild steel corrosion in 1M H2SO4. We came to know no concrete
report is available for the use this compound as corrosion inhibitor in 1M H2SO4. From
the literature the higher concentration of H2SO4 acts as pickling solution for mild steel
for electroplating, battery electrodes using sulfur containing organic compounds. Use
of these inhibitors in 1M H2SO4 will reduce the metal loss in acid medium. Kanamycin A
is an antibiotic used to treat severe bacterial infections and tuberculosis. The inhibition
efficiency of this green inhibitor was monitored
potentiodynamic polarization studies, impedance
techniques, hydrogen permeation
studies and diffuse reflectance methods.
2. Experimental Section
Mild steel specimens of size 1x4 cm2 were used for weight loss and
electrochemical studies. The aggressive solution of 1M H2SO4 (AR Grade) was used for
all the studies. The antibiotic namely Kanamycin A was purchased from the medicine
shop and used as such. The structures of the antibiotics are given in the figure 1.
Figure 1. Structure of Kanamycin A
Electrochemical experiments were cariedout
using a three electrode cell assembly
with mild steel samples as working electrode, 4cm2 area of platinum as counter
electrode and Hg/Hg2SO4/1M H2SO4 as the reference electrode. The surfaces of
corroded and corrosion inhibited mild steel specimens were examined by diffuse
reflectance studies in the region 200-700 nm using U-3400 spectrometer (UV-VIS-NIR
Spectrometer, Hitachi, Japan).
2.2. Mass loss studies
The concentrations of inhibitor used for weight loss and electrochemical study
were from 30x10-3M to 90 x10-3M. Mild steel specimens of size 1x4 cm2 were abraded
with different emery papers and degreased with trichloroethylene. The cleaned samples
were then washed with double distilled water and finally dried and kept in the
desicator. The mass loss study was carried out at room temperature for 3 hours in 1M
H2SO4. The experiments were performed in triplicate. The inhibition efficiency (IE %)
was determined by the following equation
Inhibition Efficiency (IE %)
(Wb –Wi /Wb) X 100
Where Wb & Wi are the mass loss values in the absence and presence of
2.3. Electrochemical studies
Potentiodynamic polarization measurements were done out in a conventional
three electrode cylindrical glass cell, using CH electrochemical analyzer. The solution
was deaerated for 20 minute before carryout the polarization studies. The working
electrode was kept at its corrosion potential for 10 min. until a steady state was
achieved. The mild steel surface was exposed to various concentrations of inhibitor in
100mL of 1M H2SO4 at room temperature. The inhibition efficiency (IE %) was calculated
using the equation.
Inhibition Efficiency (IE %)
(Ib –Ii /Ib) X 100
Where Ib and Ii are the corrosion current density
without and with the inhibitor
The potentiodynamic current-potential curves were noted by changing the
electrode potential automatically from -750mV to +150mV versus the open circuit
potential. The corresponding corrosion current (Icorr) was recorded. Tafel plots were
built by plotting E versus log I. Corrosion Potential (Ecorr), corrosion current density
(Icorr) and cathodic and anodic slopes (βc and βa) were calculated according to known
Impedance measurements were performed in the frequency range from 0.1 to
10000 Hz using amplitude of 20 mV and 10 mV peak to peak with an AC signal at the
open-circuit potential. The impedance diagrams were plotted in the nyquist
representation. Charge transfer resistance (Rct) and double layer capacitance (Cdl)
values were acquired from nyquist plot [25, 26]. The percentage inhibition efficiency
was calculated from the equation
Inhibition Efficiency (IE%)=
( Cdl - Cdl’ / Cdl) x 100
Where Cdl and Cdl’ are the corrosion current of mild steel with and without inhibitor
2.4. Hydrogen permeation studies
The hydrogen permeation study was monitored using an adaptation of modified
Devanathan and Stachurski’s, two compartment cell as described elsewhere .
Hydrogen permeation currents were noted in the absence and presence of inhibitors.
2.5. Diffuse reflectance spectroscopy
The surfaces of corroded and corrosion inhibited mild steel specimens were
scrutinized by diffuse reflectance studies in the region 200- 700 nm using U-3400
spectrometer [UV-VIS-NIR Spectrometer, Hitachi, Japan].
3. Results and discussion
3.1. Mass loss studies
The values of inhibition efficiency (IE%),corrosion rate (CR) and surface
coverage(θ) calculated for Kanamycin A in 1M H2SO4 at different concentrations from
loss data are
summarized in the table-1. It is noticeable that inhibition
efficiency boosts with increase in the inhibitor concentration. In addition the rate of
corrosion has reduced with increase in inhibitor concentration. Maximum inhibition
efficiency is obtained at 90x10-3 M concentrations of the inhibitor.
Table 1. Values of Inhibition Efficiency, Corrosion rate and Surface coverage for the
corrosion of mild steel in 1M H2SO4 in presence of different concentrations of
Kanamycin from mass loss measurements.
3.2. Potentiodynamic polarization studies
Polarization plots for mild steel in 1M H2SO4 containing different concentrations
of green inhibitor for two antibiotics are summarized in table -2. The values of
corrosion potential (Ecorr) , corrosion current densities (Icorr), anodic Tafel slope (βa)
,cathodic Tafel slope (βc) surface coverage(θ) and inhibition efficiency (IE%) were
calculated using polarization curves. According to the results, corrosion current (Icorr)
value diminishes with increase in the concentration of the Kanamycin drug. The
inhibition efficiency (IE %) and surface coverage (θ) increases with increase in inhibitor
concentration for all the three antibiotics. The maximum inhibition efficiency was
achieved at 90x10-3 M concentration of the inhibitor. It has been observed that both βa
βc are reduced, but the values of βc are decreased to a greater extent. This indicates
that the compound behaved as cathodic inhibitor.
2 Electrochemical parameters and Inhibition Efficiency for corrosion of mild steel
in 1M H2SO4 obtained by Polarization method in presence of different concentrations of
Kanamycin A drug.
3.3. Electrochemical impedance studies
Values of charge transfer resistance (Rct) and double layer capacitance (Cdl)
derived from Nyquist plots are shown in table 3. The values of Rct are appeared to
increase with increase in concentration of inhibitors in 1M H2SO4. It is cleared that
values of Cdl are fetched down by increasing concentrations of inhibitors in the acid.
This can be attributed to the dominant adsorption of the green inhibitor on the mild
3 Electrochemical parameters and Inhibition efficiency for corrosion of mild steel
in 1M H2SO4 obtained by Impedance method in presence of different concentrations of
3.4. UV spectral reflectance studies
The reflectance plots for polished specimen, specimen dipped in 1M H2SO4 and
various concentrations of Kanamycin are given in the figure.2. The percentage of
reflectance is maximum for polished mild steel and it progressively diminishes for the
specimen dipped in 1M H2SO4 solution. This observation unveils that the change in
surface property is due to the corrosion of mild steel in acid. Also the reflectance
percentage of steel in the presence of green inhibitor is higher than steel as immersed
in blank. This endorses that the surface property of steel
has not transformed further
due to the formation of protective layer on the mild steel surface. The reflectance
percentage declines with
increase in thickness of the inhibitor film formed on metal
surface. Similar findings has been made by Madhavan etal .
2 UV Reflectance curves of mild steel in 1M H2SO4 solution with various
Concentrations of the inhibitor.
3.5. Adsorption isotherm and thermodynamic parameters
The inhibitive action of inhibitor in extremely belligerent media is due to its
adsorption on the metal surface.
The degree of surface Coverage (θ) for different
concentrations of Kanamycin A in 1M H2SO4 has been calculated from mass
polarization and electrochemical impedance studies. The attained data was tested
graphically for fitting suitable isotherm [30-32]. Almost a straight line was obtained by
plotting log (C/θ) Vs log C shown in Figure-3, which demonstrates that the adsorption
of these compounds on steel surface observes Langmuir adsorption isotherm.
The Langmuir isotherm for the adsorbed layers is given by the equation ,
Cinh/θ =1/Kads + Cinh
Where Kads is the equilibrium constant of the adsorption/desorption process.
Adsorption equilibrium constant [Kads] and free energy of adsorption [∆G0ads] were
calculated using the equation
Kads= 1/Cinh x θ/1-θ
∆G0ads = -2.303RT log [55.5Kads]
Where 55.5 is the molar concentration of water in solution . R is the gas
constant, T is the temperature. The values of adsorption equilibrium constant [Kads]
and free energy of adsorption [∆G0ads] are given in table-4. The negative values of
[∆G0ads] pointed out that adsorption of inhibitor is spontaneous process. It is reported
that values of [∆G0ads] is of order 20 kJmol-1 or lower indicates a physisorption, those
of order of -40kJmol-1 or higher involve charge sharing or transfer from the inhibitors
to the metal surface specifies a chemisorptions [36-38]. The values of free energy of
adsorption [∆G0ads] in our experiment lies in the range -28 to -32 kJmol-1, signifying
that the adsorption is not a simple physisorption, but it may contain some other
Table 4: Gibbs free energy parameters and adsorption equilibrium constant [K] of
green inhibitor at various temperatures evaluated by weight loss method.
3.6. Hydrogen permeation measurements
Hydrogen permeation currents are recorded in H2SO4 in the absence and
presence of Kanamycin drug. This study has been taken up with a plan of selecting the
inhibitors with a view to their effectiveness on the lessening of hydrogen uptake
values of permeation current with respect to time are given in table-5.
The inhibitor brings down the permeation current to the extent of 50%. Thus a
definite correlation exists between the corrosion inhibition efficiency and the extent of
reduction in the permeation current of this compound. It is a known fact that lower βc
value for an inhibiting compound, the smaller is the corrosion and hydrogen ingress on
the metal. An increase in the βc value, leads to rise in the energy barrier for proton
discharge and increase in the evolution of hydrogen. This in turn leads to higher entry
of hydrogen through the steel surface.
Table 5: Values of permeation current for mild steel in 1M H2SO4 and in presence of
green inhibitor with respect to change in time
Permeation Current (A
3.7. Mechanism of corrosion inhibition
The adsorption of Kanamycin
onto the mild steel surface is found to be majorly
physical in nature. Physical adsorption is a process of electrostatic attraction between
charged species in the solution and the metal surface. If the metal surface is positively
charged, the adsorption of negatively charged species is facilitated. Positively charged
species can also adsorb on the positively charged metal surface with the help of
negatively charged intermediate, which adsorb first on the positively charged metal
surface and allows positively charged species to adsorb on it.
Thus the adsorption of Kanamycin may take place in two different ways :
(i) The protonated Kanamycin in acid solution may adsorb electro statically to the
anion covered mild steel surface through their protonated form.
(ii) The inhibitors may compete with acid anions for the sites at the water covered
surface and adsorb by donating electrons to the mild steel surface [40- 42].
1. The use of Kanamycin antibiotic as green corrosion inhibitor in 1M H2SO4 was
thoroughly studied using mass loss, potentiodynamic polarization, impedance
measurements and hydrogen permeation studies.
2. The adsorption of green inhibitor on mild steel surface follows Langmuir
adsorption isotherm. The adsorption of compounds on steel surface is further
confirmed by diffuse reflectance spectra.
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