Proceedings of the 7th World Congress on Mechanical, Chemical, and Material Engineering (MCM'21)
Prague, Czech Republic Virtual Conference – August, 2021
Paper No. ICCPE 110
DOI: 10.11159/iccpe21.110

Effects of Migrating Inhibitors on Corrosion of Reinforcing Steel inAggressive Environment
Albana Jano1, Valbona Hoxha1, Alketa Lame2 and Efrosini Kokalari2
1

Polytechnic University of Tirana,
Tirana/Albania
albana.jano@fin.edu.al, bonahoxha@gmail.com
2
University of Tirana
Tirana/Albania
alketalame@fshn.edu.al, efrosinikokalari@fshn.edu.al
Abstract. The durability degradation of reinforced concrete structures is one of the biggest problems hindering the breakthrough inengineering and has attracted a great deal of attention in the field of civil engineering. Corrosion issues of internal steel reinforcement
have become a top priority in durability treatment since they seriously threaten the durability and sustainability of the structure. Migrating
corrosion inhibitors (MCIs) are a good alternative to prevent or control reinforcing steel corrosion because of their moderate cost andeasy application compared with other preventive methods. Our study concerns the investigation of the protective effect of MCI; different
concentrations of butanol-1 amin-2 refer 1g/L lysine. Materials under investigation are two kind of low allow carbon steel marked as:
Steel 39, Steel 44. The corrosion media is sulfuric acid in presence of chloride ions, in form of NaCl (H2SO4 1M + Cl- 10-3M).
Potentiodynamic polarization method is used for inhibitor efficiency testing. Potentiodynamic polarization measurements showed thatthe presence of MCI in acidic solution decreases the corrosion current to a good extent. Use of this inhibitor in concentration 12 g/L
butanol-1 amin-2 with 1g/L lysine, referring the corrosion protection of steel 39 presents protection efficiency 90.52% and for steel 44
present protection efficiency 75.98% classifieds as good for this extreme aggressive conditions.
Keywords: migration inhibitor, potenciodynamic polarization, acid media, carbon steel

1. Introduction
Corrosion of reinforcing steel is a major degradation of failure in reinforced concrete structures leading to financial
losses, safety risks and environmental impact. The understanding of the mechanisms of the degradation processes of concrete
allows us to improve the design of structures to enhance durability and extend service-life.(1) Corrosion of concrete armaturecaused by acid media penetration of the coastal areas in it, through chemical and mechanical cracks, is responsible sometimes
for concrete failure, building failure and of course environmental pollution. Besides the mitigation of chemical andmechanical cracks adding migration corrosion inhibitors (MCI) to concrete mixes is a simple, time-proven, cost-effective
and environmentally friendly method of achieving significant enhancement in durability.(2) Use of MCI will be for corrosion
protection of concrete steel bars a good choice, penetrating to metal surface together with aggressive media. MCI’s provide
protection because of their ability to migrate to the depth of the metal, and form a protective, molecular layer on steel when
they come into contact with it. Most reviewers present amino-acids as a good inhibitor of acidic environment (H2SO4) inpresence of Cl¯ ions, and amino-alcohols as good migrator agents. In our study we have investigated the inhibiting effect oflysine (amino acid) (1g/L) in presence of different concentrations of amino alcohol (butanol-1 amin-2) for two kind of steel:steel 39 and steel 44.

2. Eksperimental
The aim of this study is the investigation of synergic effect for different concentration of 2- amino 1- butanol (aminoalcohol), as migrator agent, refer 1g/L L-lysine (amino acid) in protection efficiency again corrosion in these aggressive
media for steel 39 and steel 44.

ICCPE 110-1

Fig.1: The structure of lysine (inhibitor)

Fig.2: The structure of 2-amino-1-butanol (migrator)

2.1 Material under Investigation, Samples Preparation and Methods
Material under investigation are two marks of low alloy carbon steel, manufactured in KURUM factory, Elbasan,
respectively St39, St44, intended for concrete armor.
Table 1: Composition of low alloy carbon steel tested.
SiMn

CrNiCuPS

Steel 39

0.37

0.17

0.51

0.60

0.60

0.30

0.040

0.040

Steel 44

0.445

0.348

0.780

0.118

0.263

0.324

0.07200.0440Element(Mass%)

CThe samples used for the potentiodynamic measurements are prepared from steel bars in cylindrical shape with sizes(D=6mm, d=4mm) and fixed inside a Teflon tube with epoxy resin as shown in figure. For the potentiodynamic
measurements the steel samples, before fixed inside the Teflon, were polished with emery paper (250 – 1000), cleaned withbe distilled water, dried, degreased with acetone, cleaned with be distilled water again, and finally dried.(4,3)

Fig.3: Preparing of the samples for potentiodynamic measurements.

The corrosion media consists in sulfuric acid in presence of chloride ions. The concentration of acid used is 1mol/L
H2SO4 and chloride ions are 10-3mol/L Cl- (in form of NaCl) (imitation of aggressive industrial Coastal atmosphere). The
concentration ratio of inhibitor is present in table 2.

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Table 2: The matrix for potenciodynamic measurements.

Nr.

12
3
4
5Concentrations ratio of lysine /2-amino 1-butanol (g/L)
Blank+

1g/L/2g/L

1g/L/4g/L

1g/L/8g/L

1g/L/12g/L++++

Potenciodynamic measurements were carried out in a typical three-electrode electrochemical cell with an Hg/Hg2SO4
saturated K2SO4 electrode as a reference electrode and a platinum electrode as auxiliary electrode. potenciostat galvanostat
tip TACUSSEL PJT 24-2 is used for potenciodinamic measurements, potencial scan rate is 6x10-3 V/min (3,5) [Mars G.
Fontana et al., 1986], [Robert G. Kelly et a., 2002] Deaerating of the solution was realized using a stream of pure nitrogen
inside the solution for 30 min and above solution for 5 min. Corrosion current density determined using the cutting point ofTaffel extrapolation line and Faradays law, equation 1 (3,6)[Mars G. Fontana et al., 1986], [Bardal, E., 2004]:
𝑉𝑐𝑜𝑟𝑟 = (𝐾 ∗ 𝑎 ∗ 𝑖) ⁄ (𝑛 ∗ 𝐷)

(1)

Where: a - is the atomic weight of the metal (a=56g/mol), i -the current density in (μA/cm2), n -the number of electrons
exchanged during metal dissolution (n=2), D -the density in (g/cm3) (d=7.86g/cm3) and K is a constant which equals to0.00327 if corrosion rate (Vcorr) is calculated in [mm/y]. Corrosion inhibitor efficiency calculated by formula 2 (7):Inhibitor Efficiency(%) = [(CR uninhibited – CR inhibited)/ CR uninhibited] x 100(2)

Where: CR uninhibited - is corrosion rate of the uninhibited system, CR inhibited - is corrosion rate of the inhibited
system. This essentially examines the ratio of the inhibited and uninhibited corrosion rates and expresses this as a percentage.

3. Results
The results for potenciodynamic measurements are given in form of V corr in (mm/year), calculated using corrosion
current density (icorr). Corrosion current density is determined using the cutting point of Taffel extrapolation line.
Potentiodynamic polarization curves are given in figures 2 (a,b) for steel 39 and in figure 3 (a,b) for steel 44 in de-aerated
1M H2SO4 solution with 10-3M chloride ions (blank) containing different concentration ratio of 2-amino1- butanol / lysine –a-; and only different concentration of lysine –b.

ICCPE 110-3

4
3.5
3
2.5
2
1.5
1
0.5

2gL
4gL
8gL
12gL
-0.95

Steel 39log i (μA/cm2)

3.5
32.5
21.5
10.5
0-1.050.5g/L0.75g/L1g/L-1.1-0.85

0.25g/L-0.9
Potential (V)blanc

Fig.4: Potentiodynamic polarization curves for Steel 39 in de-aerated 1M H2SO4 solution with 10-3M chloride ions(blank) containing different concentration ratio of 2-amino1- butanol / lysine (a); and only different concentration oflysine (b).

3.5

33

2.52gL

2.54gL22
1.58gL10.5
0-1.05

C44,0.25g/
LC44,0.5g/L

logi (cm2/µA)

3.5

C44,0.75g/
LC44,1g/L

1.5

1-0.95

-0.85

0.5
-1.05

-0.95

-0.85
Potenciali (V)-0.75

Fig.5: Potentiodynamic polarization curves for Steel 44 in de-aerated 1M H2SO4 solution with 10-3M chloride ions(blank) containing different concentration ratio of 2-amino1- butanol / lysine (a); and only different concentration oflysine (b)The total results, in form of corrosion rates in (mm/year), calculated using corrosion current density (icorr) and protections
efficiency of different concentration of additives against corrosion, are given in Table 3.

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Table 3: Values of Vcorr and Prot.Eff. % for steel 39 and steel 44 in H 2SO4 1M and 10-3 Cl- solution with and without MCI.

Concentration ratio
2-amino 1butanol/lysineBlank
0g/L:1g/L
2g/L:1g/L
4g/L:1g/L
8g/L:1g/L
12g/L:1g/L

Mark of steel material
Steel 39
Steel 44
Vcorr
Prot. Eff. %Vcorr
Prot. Eff. %(mm /year)(mm /year)
2.32
3.31
0.49
78.88
1.03
68.88
0.581
74.96
1.131
65.83
0.288
87.59
0.949
71.33
0.247
89.35
0.822
75.17
0.22
90.52
0.795
75.98

3.1 The inhibition mechanism
The adsorption mechanism for a given inhibitor depends on such factors, as the nature of metal corrosion medium, thepH and the concentration of the inhibitor as well as the functional groups present in its molecule (8).
In case of amino acids used in our study as acidic corrosion inhibitor for low alloy carbon steel, the adsorption on anodic
sites, dedicated the free electrons on N and O (of carboxylic group) atoms.
Further, amino group is easily protonated in the acidic medium, so it could be electrostatically attracted to the cathodicsites on steel surface and hinder the hydrogen evolution reaction. Protonated amino group converted from (- NH3)+ to (NH2:), which adsorbed in anodic sites of low alloy carbon steel by free electrons of N.
The corrosion inhibition process is based on the adsorption of the amino acid molecules on the active sites and/ordeposition of the corrosion products on the alloy surface (9,10). Lysine adsorbs on surface of middle steel this mechanism:
the atoms O and N in amino acids serve as active centers for the process of adsorption on the metal surface. Availability of
no bonded (lone pair) and p-electrons in inhibitor molecules facilitate electron transfer from the inhibitor to the metal. A
coordinate covalent bond involving transfer of electrons from inhibitor to the metal surface may be formed. The strength ofthe chemisorptions bond depends upon the electron density on the donor atom of the functional group and also thepolarizability of the group. When an H atom attached to the C in the ring is replaced by a substituent group (–NH2, or COOH)
it improves inhibition (11).

4. Discussion
By observation of shapes of the anodic and cathodic polarization curves in the presence of lysine + butanolamina
provides information about the inhibitor action in corrosion processes. The examination of figure 2 –a- and figure 3 -a- showsthat the MIC (mix of amino-alcohol and lysine) functioned via a mixed-inhibition mechanism; it worked as well as anodicand cathodic inhibitor. The (amino-alcohol), as migrator agent, seems to play an important role in specifying the areas ofanodic adsorption of inhibitor (the rest potential become more positive increasing the concentration of amino-alcohol) and
improve the anodic surface coverage (anodic branch come down increasing the concentration of amino-alcohol) (12, 13).
Clearly the presence of amino-alcohol as migrator agent improves the inhibition effect of lysine, even in low concentration.

5. Conclusions
The MIC (mix of amino-alcohol and methionine) functioned via a mixed-inhibition mechanism.
Cathodic: Aminogroup protonated in the acidic media electrostatically attracted to the cathodic sites on steel surface and hinder the hydrogenevolution reaction.
Anodic: Adsorption on anodic sites, dedicated the free electrons on N and O (of carboxylic & hydroxyl group) atoms.
The presence of amino-alcohol as migrator agent improves the inhibition effect of lysine, specifying the areas of anodic
adsorption of inhibitor and improves the anodic surface coverage.

ICCPE 110-5

The corrosion protection efficiency of MIC (combination of an amino-alcohol and amino-acid) for steel 39 and steel 44
corrosion in 1M H2SO4 solution in presence of 10-3Cl- ions realized in ratio 12g/L amino alcohol: 1g/L amino acid wasrespectively 90.52% and 75.98% and corrosion rate was respectively 0.22 mm/year and 0.795 mm/year.

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[2] B. Bavarian, L. Reiner, Corrosion Protection of Steel Rebar in Concrete using Migrating Corrosion Inhibitors, MCI
2021 & 2022, 2002, 2-3.
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[6] E. Bardal, Engineering Materials and Processes, Corrosion and Protection, Springer-Verlag limited ISBN 1-855233758-3, London Berlin Heidelberg, 2004,5-10.
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[10] G.Bereket, A. Yurt, Corrosion Science 43; 1179, 2001,.
[11] Azza El-Sayed El-Shenawy, Corrosion inhibition of lysine as basic amino acid on 316L stainless steel in 0.5 M H2SO4
solution, Journal of American Science, 2011, http://www.americanscience.org[12] A.Lame, E. Kokalari, A. Jano, Migration Corrosion Inhibitor Agains Premature Failure Of Reinforced Concrete
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ICCPE 110-6