Study of corrosion inhibition of C38 steel in 1 M HCl solution by polyethyleneiminemethylene phosphonic acid
Int J Ind Chem
DOI 10.1007/s40090-017-0123-2
RESEARCH
Study of corrosion inhibition of C38 steel in 1 M HCl solution
by polyethyleneiminemethylene phosphonic acid
Merah Salah1,2 • Larabi Lahcène1 • Abderrahim Omar3 • Harek Yahia1
Received: 2 April 2016 / Accepted: 24 May 2017
The Author(s) 2017. This article is an open access publication
Abstract A new class of corrosion inhibitors, namely,
polyethyleneiminemethylene phosphonic acid (PEIMPA),
was synthesized and its inhibiting action on the corrosion
of C38 steel in 1 M HCl at 30 C was investigated by
various corrosion monitoring techniques such as weight
loss measurements, potentiodynamic polarization, linear
polarization resistance (Rp), and surface analysis (SEM and
EDX) which are used to characterize the steel surface.
Weight loss measurements revealed that the presence of
PEIMPA increases the inhibition efficiency by decreasing
the corrosion rate. Tafel polarization study showed that the
inhibitor acts as a mixed-type inhibitor. Adsorption of
PEIMPA on the carbon steel surface was found to obey the
Langmuir isotherm. Some thermodynamic functions of
dissolution and adsorption processes were also determined
and discussed. The SEM results showed the formation of
protective film on the mild steel surface in the presence of
PEIMPA. The results obtained from different tested techniques were in good agreement.
Keywords Corrosion Inhibition C38 steel Phosphonic
acid
& Merah Salah
1
2
3
Laboratory of Analytical Chemistry and Electrochemistry,
Department of Chemistry, Faculty of Science, Tlemcen
University, Tlemcen, Algeria
Department of Process Engineering, Faculty of Technology,
Sai‹ da University, Sai‹ da, Algeria
Laboratory of Separation and Purification Technology,
Department of Chemistry, Faculty of Science, Tlemcen
University, Tlemcen, Algeria
Introduction
Study of organic corrosion inhibitor is an attractive field
of research due to its usefulness in various industries.
Acid is widely used in various industries for the pickling
of ferrous alloys and steels. Because of the aggressive
nature of the acid medium, the inhibitors are commonly
used to reduce acid attack on the substrate metal. Most
of the reported corrosion inhibitors are organic compounds containing O, N, S, and P [1–14] in their
structures. The phosphoric functions are considered to be
the most effective chemical group against corrosion
process [15]. The use of organic phosphonic acids to
protect carbon steel against corrosion has been the subject of various works [16–26]. Aminomethyl-phosphonic
acids are excellent sequestering agents for electroplating,
chemical plating, degreasing, and cleaning. It was shown
that piperidin-1-yl-phosphonic acids (PPA) and (4phosphono-piperazin-1-yl) phosphonic acid (PPPA) are
used to reduce the corrosion of iron in a NaCl medium,
even if PPPA is more efficient than PPA [27]. In the
present investigation, the influence of polyethyleneiminemethylene phosphonic acid (PEIMPA) as a
corrosion inhibitor of carbon steel in 1 M HCl has been
systematically studied by weight loss measurements,
potentiodynamic polarization studies, and surface analysis (SEM, EDX). Results are reported and discussed.
Experimental
Polyethyleneiminemethylene phosphonic acid polymer
was synthesized (see Scheme 1) from commercially
available Lupasol P (polyethylenimine) according to the
Moedrizer–Irani reaction [28]. The synthesis was
123
Int J Ind Chem
Scheme 1 Synthesis of polyethyleneiminemethylene phosphonic acid from Lupasol P
performed in distilled water under microwave irradiation.
In a quartz reactor, a mixture of polyethylenimine (Lupasol P, 80 mmol, 3.44 g), phosphorous acid (80 mmol,
6.68 g), and hydrochloric acid–water (1:1) solution
(12 mL) was vigorously stirred and then irradiated
(150 W) in a glass cylinder reactor for 1 min. A
formaldehyde aqueous solution (160 mmol) was added
and irradiated for 8 min.
Then, the precipitation was washed with distilled water
to remove unreacted reagents. Finally, phosphonic-modified Lupasol P was washed three times with distilled water
and ethanol. After drying, the solid was further pulverized
to give a brown powder.
The structure and purity were identified and characterized by elemental microanalysis (Table 1) and 1H, 13C, and
31
P NMR spectroscopy. The spectra showed the expected
signals due to the polyethylenimine skeleton and methylene phosphonic units as matched to the proposed structure
(Scheme 1).
NMR spectral data: 1H NMR d (ppm): 4.92 (N–CH2);
2.33 (CH2–P); 1.6 NH. 13C NMR d (ppm): 82.16 (N–CH2),
52.1 (CH2–P). 31P NMR d (ppm): 3.91. The presence of
phosphonic acid was confirmed by FTIR measurement: the
polymer displays characteristic bonds for P–O–C at
1050 cm-1, P–OH at 2372, and 2338 cm-1 189 and P = O
at 1172 cm-1.
Elemental microanalysis suggests the structure made of
fragment of the phosphonic acid polymer, corresponding
after calculation to x = 5 and y = 9 (Scheme 1).
A 1 M HCl solution was prepared from an analytical
reagent grade of HCl 37% and double-distilled water and
was used as corrosion media in the studies. Note that the
solubility of polyethyleneiminemethylene phosphonic acid
is very high in this medium.
For the weight loss measurements, the experiments were
carried out in the solution of 1 M HCl (uninhibited and
inhibited) on carbon steel containing 0.30–0.35% C,
0.15–0.35% Si, 0.035% S, 0.5–1.0% Mn, and 0.035% P.
Table 1 Elemental
microanalysis of
polyethyleneiminemethylene
phosphonic acid
123
Microanalysis
Sheets with dimensions 20 mm 9 10 mm 9 2 mm were
used. They were polished successively with different
grades of emery paper up 1200 grade. Each run was carried
out in a glass vessel containing 100 ml test solution. A
clean weight mild steel sample was completely immersed
at an inclined position in the vessel. After 4 h of immersion
in 1 M HCl with and without the addition of inhibitor at
different concentrations, the specimen was withdrawn,
rinsed with double-distilled water, washed with acetone,
dried, and weighed. The weight loss was used to calculate
the corrosion rate in milligrams per square centimeter per
hour.
Electrochemical experiments were carried out in a
glass cell (CEC/TH Radiometer) with a capacity of
500 ml. A platinum electrode and a saturated calomel
electrode (SCE) were used as a counter electrode and a
reference electrode. The working electrode was in the
form of a disc cut from mild steel under investigation
and was embedded in a Teflon rod with an exposed area
of 0.5 cm2. Potentiodynamic polarizations were conducted in an electrochemical measurement system
(VoltaLab 21) which comprises a PGP201 potentiostat, a
personal computer, and VoltaMaster4 software. The
polarization resistance measurements were performed by
applying a controlled potential scan over a small range
typically ±15 mV with respect to Ecorr with a scanning
rate of 0.5 mV s-1. The resulting current is linearly
plotted vs. potential, the slope of this plot at (...truncated)
