Effect of Thermal Treatment of Two Titanium Alloys (Ti-49Al & Ti-51Al) on Corrosion Behavior in 0.01 M Various Acidic Media

International Journal of Chemistry, Mathematics and Physics (IJCMP)
[Vol-9, Issue-2, Apr-Jun, 2025]
https://dx.doi.org/10.22161/ijcmp.9.2.3
ISSN: 2456-866X
Int. j. chem. math. phys.
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Effect of Thermal Treatment of Two Titanium Alloys (Ti-
49Al & Ti-51Al) on Corrosion Behavior in 0.01 M Various
Acidic Media
Rabab M. Abou Shahba1
, Amal S.I. Ahmed1
, Azza El-Sayed El-Shenawy1
* , Waffa A.
Ghannem2
and Safaa M. Tantawy1
1
Chemistry Department, Faculty of Science (Girls), Al-Azhar University, Nasr City, Cairo, Egypt
2
Physical Chemistry Department, Central Metallurgical Research and Development Institute (CMRDI)
*Corresponding author
Received: 10 May 2025; Received in revised form: 06 Jun 2025; Accepted: 12 Jun 2025; Available online: 18 Jun 2025
©2025 The Author(s). Published by AI Publications. This is an open access article under the CC BY license
(https://creativecommons.org/licenses/by/4.0/)
Abstract— In this paper, the effect of thermal treatment of (Ti-49Al & Ti-51Al) alloys on corrosion
behavior in 0.01M of H2SO4, H3PO4, HNO3 and HCl solutions was investigated. Potentiodynamic
polarization measurements, were performed for the two alloys in 0.01 M acidic media at room
temperature. The polarization curves indicated three regions. The first region, the active dissolution region
was observed from – 2000 to ~ - 700 mV(SCE), the second region, signifying the transition from active
dissolution to a passive state on the electrode surface and the third region, a trans-passive region, which
the oxygen started to evolve and the current density increased sharply with further increase in potential.
The results of potentiodynamic polarization curves, clearly indicate that the corrosion resistance for
different alloys decreases as follows: a < f < e < d < b < c, this means that alloys (a, f and e), which
have one phase structure ( 100 % γ), shows better corrosion resistance than alloys (d, b and c), which have
dual phase structure (α + γ). The surface morphology was examined by scanning electron microscope
(SEM) and energy dispersive X-ray analysis (EDX) of two alloys used to confirm the corrosion mechanism.
The SEM results confirmed the corrosion of Ti-Al alloys due to uniform corrosion in 0.01 M HCl solution.
Keywords— Acidic media, Surface Morphology, Titanium alloys, Thermal Treatment.
I. INTRODUCTION
Ti is one of the most abundant metals on the earth and its
alloys are commonly used in the shipping industry,
chemical and medical industries due to its outstanding
corrosion resistance, higher specific strength and
cryogenic properties [1]. Manufacturing of large
aeronautical titanium structural components by the
wrought based traditional advanced manufacturing
processes, has been recognized both technologically
difficult and economically expensive [1, 2]. Ti alloys, as a
kind of high strength ratio material widely used for the
safety-critical components in the aero engines, exhibit
microstructural sensitive fatigue performance when
subjected to long term cyclic loadings [3].
A high-quality alloy of titanium is used to manufacture the
thin-walled pipes of condensers, thin pipers of heat
exchangers and mufflers of diesel engines in submarines
[1]. They have been made faster in the marine industry,
hydrocarbon extraction devices in the offshore petrol-
chemical industry, heat exchangers in desalination plants
and cooling systems in seawater-cooled power plants [3].
High quality titanium alloys can operate for a long time
even at a temperature above 600 o
C. A huge amount of
heat is generated during the machining of Titanium alloys
due to its low machinability and thermal conductivity.
Heat treatment mainly includes solution treating, surface
treatment, annealing, aging and thermochemical treatment.
Heat treatment, is a combination of industrial and metal
working processes used to modify physical and chemical
characteristics of a material. Heat treatment consists of

Shahba et al. International Journal of Chemistry, Mathematics and Physics (IJCMP), Vol-9, Issue-2 (2025)
heating the materials at a predefined temperature to
achieve the desired characteristics such as hardening and
softening of the materials [1]. Heat treatment of Titanium
alloys has been investigated by Peng Cao and Laichang
Zhang [4]. Titanium and its Alloys: Metallurgy, Heat
Treatment and Alloy Characteristics have been
investigated [5].
Ti has two allotropic forms, high-temperature body-
centered cubic(BCC)β-phase and low temperature α-phase
with a hexagonal-close-packed(HCP)structure. The
transition from α + β to 100 % β- phase, occurred at ~ 882
o
C for unalloyed Ti. α/β- alloys, this class of alloys is
defined as the region between the boundary of the α-
alloys and the metastable β- alloys-marten site is formed
when quenching from temperatures high in α + β phase
filed or higher [5]. Titanium alloys that consist of only the
alpha phase are commonly used in industrial applications
where corrosion resistance is a primary concern [6].
Aluminum also is an active metal, whose resistance to
corrosion depends on the passivity produced by a
protective oxide film. Al is passive only in the pH range of
about 4 to 9 [7]. The limits of passivity depend on the
temperature and the form of oxide present, the various
forms of aluminum oxide e.g.Al2O3 & AlO2, all exhibit
minimum solubility at about pH 5. At higher temperatures,
thicker films are formed; these may consist of a thin
structure less barrier layer next to the Al and a thicker
crystalline layer next to the barrier layer [8]. A Critical
Review on Heat Treatment of Aluminum Alloys [9].
The aim of this study, is to investigate the effect of
the thermal treatment of two Ti-Al alloys on corrosion
behavior in 0.01 M of different acids.
II. EXPERMENTAL
2.1. Materials
Two Ti alloys were used to evaluate the effect of thermal
treatment. Chemical composition was determined by X-ray
fluorescence and the surface area of Ti alloys are shown in
Table 1.
Table 1: The chemical composition of the samples used, mass % & surface area
Surface Area(cm2
)
Cr
Mn
Si
H
O
N
Al
Ti
Samples
1.54
‹ 0.01
0.021
‹ 0.01
0.001
0.115
0.0057
49.0
Bal.
I (Ti - 49 Al)
1.54
‹ 0.01
0.02
‹ 0.01
0.003
0.114
0.004
51.0
Bal.
II (Ti – 51 Al)
The two sample alloys, were prepared by argon arc
melting ( The arc melting process takes place in a
cylindrical chamber that can be filled with argon gas after
the air is evacuated by an integrated vacuum pump) with a
non-consumable tungsten electrode, using high purity Ti
and Ti chips (99.9 % Ti & 99.9 % Al) to make a 100 gm.
button ingot. The chemical composition of the ingot was
determined by X-ray fluorescence type ARL 9400.
Switzerland. All samples were cut from the button ingots
and wrapped with tantalum foil and used for heat
treatment. They were treated with heat in a vertical furnace
equipped with a vacuum system under high purity argon.
Prior the heat treatment, the furnace was evaluated down
to 5 x 10-3
pa and then back filled with argon. The
previous circular electrodes were fixed to glass tubing with
araldite adhesive. The electrical contact was made through
a thick copper wire soldered to the inner side of the
electrodes. Prior to each experiment, the surface of the
working electrodes was performed by polishing with
different grades of emery papers (800-1200), then diamond
past (1 μm), washing by distilled water and ethanol, then
quickly inserted in the cell. The counter electrode was
platinum sheet, and the potential was recorded relative to
saturated calomel electrode (SCE).
Test solutions: 0.01 M of oxy and halogen acids which are
sulfuric, phosphoric, nitric and hydrochloric acids.
2.2. Measurements and instruments
In order to study the effect of heat treatment on the
microstructure and corrosion properties of the two alloys,
three techniques were used: potentiodynamic polarization
technique, scanning electron microscope (SEM) and
energy dispersive x-ray analysis. Anodic and cathodic
potentiodynamic polarization measurements were
performed for the samples using electronic potentiostate
(PGZ301 Dynamic EIS Voltammetry). The measurements
were conducted at scanning rate 15 mV/s. All
measurements were performed in freshly prepare aerated
solutions at room temperature and the anodic E/log I
curves were swept from (-2000 mV to +1500 mV). The
morphology of titanium alloys, were examined before and
after immersion in test solutions, using SEM. The
identification of the elements present on the surface of
specimen before and after immersion in 0.01 M

hydrochloric acid solutions and heat treatment, was using
energy dispersive X-ray analysis.
III. RESULTS AND DISCUSSION
Surface heat treatment change the phases and grain size of
the alloys are tabulated in Table 2. The surface
morphology of the tested alloys as-received and after heat
treatment, were shown in Fig. 1. Literature on the Ti-Al
alloys, with and without surface treatment, showed
corrosion problems [10]. Therefore, it is essential to
understand the corrosion characteristics of Ti alloys in
detail under different acidic solutions.
Table.2: The heat treatment conditions phases and grain size of the heat treated alloys
Alloy No.
Alloy composition Heat treatment [* furnace cooled] Phases
γ
Grain size μm
a Ti – 51 Al As received γ 100% 22
b Ti – 49 Al Heat to 1435 o
C for 5 minutes & f.c* α2 25% + γ 75% 430
c Ti – 51 Al Heat to 1365 o
d Ti – 51 Al Heat to 1365 o
e Ti – 51 Al Heat to 1150 o
C for 60 minutes & f.c* γ 100% 55
f Ti – 51 Al Heat to 1200 o
C for 10 hours & f.c* γ 100% 130
* furnace cooled
(a) (b)
(c) (d)

(e) (f)
Fig.1: SEM morphology of tested samples, (a) as received Ti-51Al alloy, γ phase=100%, (b) Ti-49Al alloy, heat treated at
1435 o
C for 5 minutes, (c) Ti-51Al alloy, heat treated at 1365 o
C for 30 minutes, (d) Ti-51Al alloy, heat treated at 1365 o
C for
3 minutes, (e) Ti-51Al alloy, heat treated at 1150 o
C for 60 minutes, (f) Ti-51Al alloy, heat treated at 1200o
C for 10 hours
3.1. Anodic and cathodic potentiodynamic polarization
measurements
The potentiodynamic polarization measurements were
performed for two alloys and carried out in 0.01 M of
sulfuric, phosphoric, nitric and hydrochloric acids
solutions at room temp., with a scanning rate 15 mV/s.
Ranging from (-2000 mV to +1500 mV).
In the present part, potentiodynamic polarization is utilized
to give information about the corrosion potential (Ecorr.),
corrosion current density (Icorr.), anodic, cathodic Tafel
slopes and corrosion rate for all tested alloys.
Consideration of the curves of Fig. 2, shows the variation
of electrode potential with current density in 0.01 M of
different tested acidic solutions at different heat treatment
cycles. The electrochemical parameters determined for all
tested alloys are summarized in Table 3.
Table.3: The electrochemical parameters of Ti-Al alloys in different acidic in 0.01 M of different acidic solutions
Alloy No.
0.01 M Acids
Ecorr.
(mV)
Icorr.
(mA/cm2
)
Tafel slopes Corrosion rate
(C.R) μm/y
βa(mV) βc(mV)
a
H2SO4 -629.3 0.0053 566.5 -281.5 61.89
H3PO4 -634.5 0.0023 615.7 -300.9 27.15
HNO3 -589.2 0.1108 509.4 -949.7 129.5
HCl -628.4 0.0038 525.9 -328.2 44.34
b
H2SO4 -818.8 31.2718 693.2 -885.7 365.7
H3PO4 -718.8 0.0050 497.9 -280.1 58.18
HNO3 -789.4 0.0088 1086.5 -265.4 103.0
HCl -637.7 0.0592 732.5 -705.0 692.5
c
H2SO4 -696.0 11.7814 559.7 -500.8 137.7
H3PO4 -781.3 0.0031 463.8 -280.6 36.02
HNO3 -730.5 0.0044 677.9 -301.8 51.32
HCl -776.3 0.1788 400.1 -883.8 209.1
d
H2SO4 -855.4 0.0092 1632.8 -327.4 107.7
H3PO4 -735.9 0.0030 552.3 -297.4 35.42
HNO3 -670.5 0.0069 638.4 -339.3 81.10
HCl -629.5 0.0590 580.2 -799.1 689.6
e H2SO4 -730.4 0.0086 1026.5 -301.6 100.7

H3PO4 -790.0 0.0042 607.0 -321.5 49.68
HNO3 -710.9 0.0060 712.0 -323.2 69.97
HCl -591.3 77.9468 488.2 -1087.9 911.6
f
H2SO4 -595.1 7.0159 213.8 -1517.1 82.05
H3PO4 -734.6 2.1003 705.2 -722.1 24.56
HNO3 -513.9 3.9133 238.8 -1058.6 45.66
HCl -724.6 8.4955 2273.6 -453.5 99.36
Analysis of the polarization curves Fig. 2 and Table 3, show a similar character of potentiodynamic curves for as-received
and heat-treated alloys and the values of the parameters are almost similar in received alloy in all acids.
(a) (b)
(c)
(d)
(e) (f)
Fig.2: Potentiodynamic polarization curves of the of tested alloys in 0.01 M of Acidic solutions,
(a) as received Ti-51Al alloy; (b) Ti-49Al alloy, heat treated at 1435 o
C for 5 minutes; (c) Ti-51Al alloy, heat treated at 1365
o
C for 30 minutes; (d) Ti-51Al alloy, heat treated at 1365 o
C for 3 minutes; (e) Ti-51Al alloy, heat treated at 1150 o
C for 60
minutes; (f) Ti-51Al alloy, heat treated at 1200o
C for 10 hours

Data recorded in Table 3, reveal that the corrosion rate of
all tested alloys depends not only on the acid used, but also
on the surface heat treatment and immersion time. The
effect of immersion time and temperature on the corrosion
behavior of certain aluminum alloys was examined [11].
All polarization curves exhibit well-developed Tafel
behavior in the active region with E α log Ia. The results
obtained show that, the cathodic current density is due to
hydrogen evolution. It is clear from the curves that, the
polarization curves indicated three regions. The first
region, active dissolution region was observed from –
2000 to ~ - 700 mV(SCE), where the potential-current
relation was linear and well-defined Tafel slope.
The second region, signifies the transition from active
dissolution to a passive state on the electrode surface. And
the third region is a trans-passive region. The oxygen
started to evolve and the current density increased sharply
with a further increase in potential. Increasing the acid
concentration, shifts the critical current density, and
active-passive transition potential region toward the active
direction [12-13]. So all tested acids follow the order:
H3PO4 < HNO3 < H2SO4 < HCl
Increasing the acid concentration, shifts the critical current
density, active-passive transition potential region toward
the active direction. The composition of the passive film
for Ti-Al alloy formed in the different acids used is: the
titanium oxide layer, which may be described as an n-type
semiconductor [14]. The results of potentiodynamic
polarization curves and Table 3, clearly indicate that the
corrosion resistance for different alloys decreases as
follows: a < f < e < d < b < c This means that alloys (a, f
and e), which have one phase structure ( 100 % γ), shows
better corrosion resistance than alloys (d, b and c), which
have dual phase structure (α + γ).
Regarding the (γ) grain size, it can be easily seen that as
the grain size increases the corrosion resistance decreases
(for alloys a, f and e). For alloys d, b and c, with (α + γ)
phase structure by increasing the percentage of α phase,
the corrosion resistance decreases. These results are in
good agreement [15, 16], phosphate is formed on the oxide
surface and prevents dissolution.
3.2. Spectroscopic analysis
3.2.1– SEM analysis
To confirm the corrosion mechanism of the Ti-Al alloys
under various environmental conditions, the corroded
specimens tested were observed under SEM, Fig. 3 shows
the SEM images which describe the morphology of the
corroded surfaces of tested electrodes after exposure to
0.01 M hydrochloric acid solution, at room temp. As can
be seen the alloys corroded uniformly in 0.01 M
hydrochloric acid solution, which is the reason for the
corrosion of Ti-Al alloys under an acidic solution. SEM
results are in good agreement with the potentiodynamic
polarization data. Hence, SEM results confirm that, the
degradation of Ti-Al alloys takes place due to uniform
corrosion in the hydrochloric acid solution.
3.2.2 - EDX analysis
It is important to take into consideration, the percentages
of the elements and oxide film formed on the surface of
the alloys electrode. This percentages were obtained from
elemental composition by energy dispersive x- ray
analysis.
Fig. 4, shows the (EDX), for Ti-Al alloys tested in 0.01 M
hydrochloric acid solution, at room temperature, it can
easily show that, the corrosion products formed on the
surface of the tested alloys, consist of TiO2 and Al2O3 in
addition to some chloride appears on the surface of
samples heat treated Ti-51Al alloy at 1365 o
C for 30
minutes (c) and heat treated Ti-51Al alloy at 1200 o
C for
10 hours (f), that explained the healing process happened
after uniform corrosion occurs.

In the active region I (dissolution) In the passive region III (healing)
Fig.(3): Surface morphology of heat treated Ti-Al alloys after corrosion tests in 0.01 M HCl solution, at room temperature,
a) as received Ti-51Al alloy, (b) Ti-49Al alloy, heat treated at 1435 o
C for 5 minutes,
(c) Ti-51Al alloy, heat treated at 1365 o
C for 30 minutes, (d) Ti-51Al alloy, heat treated at 1365 o
C for 3 minutes,
(e) Ti-51Al alloy, heat treated at 1150 o
C for 60 minutes, (f) Ti-51Al alloy, heat treated at 1200o
C for 10 hours

(a)
(b)
(c)

(d)
(e)
(f)
Fig. (4): EDX spectra of tested samples: (a) as received Ti-51Al alloy; (b) Ti-49Al alloy, heat treated at 1435 o
C for 5
minutes, in 0.01 M HCl solution; (c) Ti-51Al alloy, heat treated at 1365 o
C for 30 minutes, in 0.01 M HCl solution; (d) Ti-
51Al alloy, heat treated at 1365 o
C for 3 minutes, in 0.01 M HCl solution; (e) Ti-51Al alloy, heat treated at 1150 o
C for 60
minutes, in 0.01 M HCl solution; (f) Ti-51Al alloy, heat treated at 1200o
C for 10 hours, in 0.01 M HCl solution

IV. CONCLASION
The following major findings are summarized:
1- The effect of surface heat treatment on the
corrosion behavior of two Ti alloys (Ti-49Al &
Ti-51Al) was investigated by using
potentiodynamic polarization technique, (SEM)
and (EDX).
2- The potentiodynamic polarization measurements
were performed for the two alloys and carried
out in 0.01 M of sulfuric, phosphoric, nitric and
hydrochloric acids solutions. The polarization
curves indicated three regions. The first region,
the active dissolution region was observed from
– 2000 to ~ - 700 mV(SCE), the second region,
signifying the transition from active dissolution
to a passive state on the electrode surface and the
third region, a trans-passive region, which the
oxygen started to evolve and the current density
increased sharply with further increase in
potential.
3- The results of potentiodynamic polarization
curves, clearly indicate that the corrosion
resistance for different alloys decreases as
follows: a < f < e < d < b < c, this means that
alloys (a, f and e), which have one phase
structure ( 100 % γ), shows better corrosion
resistance than alloys (d, b and c), which have
dual phase structure (α + γ).
4- SEM results confirm the corrosion mechanism of
Ti-Al alloys takes place due to uniform corrosion
in hydrochloric acid solution.
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Effect of Thermal Treatment of Two Titanium Alloys (Ti-49Al & Ti-51Al) on Corrosion Behavior in 0.01 M Various Acidic Media

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