S. AL-QAWABAH et al: EFFECT OF HEAT TREATMENT ON THE GRAIN SIZE, MICROHARDNESS ...
785–790
EFFECT OF HEAT TREATMENT ON THE GRAIN SIZE,
MICROHARDNESS AND CORROSION BEHAVIOR OF THE
COLD-WORKING TOOL STEELS AISI D2 AND AISI O1
VPLIV TOPLOTNE OBDELAVE NA VELIKOST KRISTALNIH ZRN,
MIKROTRDOTO IN KOROZIJSKE LASTNOSTI DVEH VRST
(AISI D2 IN AISI O1) HLADNO DEFORMIRANIH ORODNIH JEKEL
Safwan Al-Qawabah
1*
, Ahmad Mostafa
2
, Aiman Al-Rawajfeh
3
,
Ubeidulla Al-Qawabeha
1
1
Mechanical Engineering Department, Al-Zaytoonah University of Jordan, Amman, Jordan
2
Mechanical Engineering Department, Tafila Technical University, Tafila 66110, Jordan
3
Chemical Engineering Department, Tafila Technical University, Tafila 66110, Jordan
Prejem rokopisa – received: 2020-03-23; sprejem za objavo – accepted for publication: 2020-07-15
doi:10.17222/mit.2020.035
The current work focuses on the effect of heat treatment on the grain size, microhardness and corrosion behavior of AISI D2 and
O1 tools steels. Samples of the investigated steels were subjected to different heat treatment (quenching and tempering) regimes.
The hardening temperatures for AISI D2 steel were in the range 850–1000 °C with 50 °C step and in the range 780–870 °C with
30 °C step for AISI O1 steel. The tempering temperatures were fixed for AISI D2 and O1 specimens at 550 °C and 450 °C, re-
spectively, to investigate the influence of the hardening temperature only. The results show that the grain size of heat-treated
steels decreased by increasing the hardening temperature and thus the microhardness number increased due to the dense
grain-boundary areas in the fine structures. The corrosion behaviors of the steel specimens were assessed in 0.1-M HCl solution
using a potentiostatic polarization technique. The immersed AISI D2 specimens showed better corrosion resistance than that of
AISI O1 due to the presence of high alloying elements, which may help in forming a protective layer against corrosion. The cor-
rosion rates of the coarse-grained structures were less than that of the fine-grained structures, because the finer the grains, the
greater the anodic areas, which leads to higher corrosion rates.
Keywords: microhardness, heat treatment, grain size, corrosion resistance
V prispevku so se avtorji osredoto~ili na dolo~itev vpliva toplotne obdelave dveh vrst orodnih jekel (AISI D2 in O1) na njuno
velikost kristalnih zrn, mikro trdoto in odpornost proti koroziji. Vzorce jekel so toplotno obdelali pri razli~nih re`imih kaljenja
in popu{~anja. Za jeklo AISI D2 so za temperaturno obmo~je austenitizacije izbrali temperature med 850 in1000 °C v korakih
po 50 °C, medtem ko so za jeklo AISI O1 izbrali obmo~je med 780-870 °C v korakih po 30 °C. Za ugotavljanja vpliva
utrjevanja obeh vrst jekel so izbrali dve temperaturi popu{~anja in sicer 550 °C in 450 °C. Rezultati raziskav so pokazali, da se
velikost zrn toplotno obdelanih jekel zmanj{uje z nara{~ajo~o temperaturo austenitizacije in zato nara{~a tudi mikrotrdota zaradi
ve~je gostote kristalnih mej v drobnozrnati mikrostrukturi jekel. Korozijsko obna{anje vzorcev jekel so analizirali v 0,1 M
raztopini HCl s potenciostati~no polarizacijo. V raztopino potopljeni vzorci jekla AISI D2 so imeli bolj{o odpornost proti
koroziji kot vzorci jekla AISI O1 zaradi ve~je vsebnosti zlitinskih elementov, ki pomagajo pri tvorbi za{~itne plasti. Hitrost
korozije grobo zrnatih mikrostruktur jekel je bila manj{a kot tistih s fino zrnato mikrostrukturo, ker imajo le te ve~ja anodna
podro~ja, kar vodi do vi{jih korozijskih hitrosti.
Klju~ne besede: mikrotrdota, toplotna obdelava, velikost zrn, odpornost proti koroziji
1 INTRODUCTION
The grain size of structural tool steels significantly
affects their mechanical properties by the well-known
Hall-Petch relationship.
1,2
without modification of the
chemistry of the base alloy.
3
Generally, the mechanical
performance deteriorates in large-grained structures, be-
cause of the dislocation motion that creates the potential
for extensive plastic flow.
4
However, the large-grained
structures are accompanied by a low volume of grain
boundaries and are expected to be less active in corrosive
environments for pure iron.
5
High corrosion resistance
results in the long service life of tool-steel parts. The
AISI D2 and O1 steels are designated as cold-work tool
steels and are used in making tools and dies for blanking,
punching, forming and other operations requiring high
compressive strength and excellent wear resistance.
6
De-
spite the good mechanical properties of D2 and O1
steels, the lifetime of parts fabricated from these steels is
negatively affected by the increase in the severity of
working conditions and corrosive operating environ-
ments.
7
Such steels are generally used in different indus-
tries where they come into contact with mineral acids
such as HCl, which are used for the cleaning and pick-
ling of metal surfaces.
8
Therefore, the need for improv-
ing the corrosion performance has increased rapidly in
recent years, opening up a considerable number of op-
portunities for new technologies to resolve such a prob-
lem.
9
There are some drawbacks associated with the ef-
Materiali in tehnologije / Materials and technology 54 (2020) 6, 785–790 785
UDK 67.017:621.791.725:669.715 ISSN 1580-2949
Original scientific article/Izvirni znanstveni ~lanek MTAEC9, 54(6)785(2020)
*Corresponding author's e-mail:
safwan.q@zuj.edu.jo (Safwan Al-Qawabah)

fects of grain size on corrosion resistance, which arise
largely from the difficulty in isolating grain size effects
from other microstructural changes caused by grain size
control processes.
3
To the authors’ knowledge, very lim-
ited information on the effects of grain size on the corro-
sion behavior of AISI D2 tool steel can be found in the
literature, whereas no information related to AISI O1
tool steel can be found. For instance, Yasavol and
Jafari.
10
observed an improved corrosion resistance of a
friction-stir-welded AISI D2 steel due to the high vol-
ume fraction of low-angle grain boundaries in the
ultrafine-grain layers. This work aims at studying the ef-
fect of different grain sizes, obtained by systematic hard-
ening and tempering thermal treatment schemes, on the
corrosion behavior of AISI D2 and O1 tool steels. The
heat-treatment and corrosion-rate results can be of high
importance for the use of D2 and O1 steels in industry
under corrosive environment. The controlled grain size,
obtained by an optimized heat treatment procedure,
could offer a low-cost corrosion inhibitor for the investi-
gated steel grades.
2 EXPERIMENTAL PART
An equivalent to AISI D2 and O1 cold-working tool
steel discs of 20 mm diameter, provided from ASSAB
Steels with the chemical composition given in Table 1
(in w/%), were subjected to several heat treatment
schemes. Schematic illustrations of the thermal treatment
cycles are shown in Figure 1. The treated specimens
were prepared for metallographic investigation by
mounting them in hot-setting epoxy mounts, polished us-
ing gradual numbers of sandpapers from 200 to 2000 grit
size, and etched with Nital solution (3 % v/v nitric acid
in methanol) for 15 s to 30 s.
The etching chemicals were provided by Fisher Sci-
entific Company. The microstructure of the treated speci-
mens was examined using a Nikon Epiphot 200 metallur-
gical optical microscope (OM) at 200× magnification.
Microhardness of the treated specimens was measured
using a Highwood HWDM-3 (TTS Unlimited Inc., Ja-
pan) Vickers micro-indentation instrument under 500 g
of load. An average of three values was taken for each
measurement to ensure data accuracy. The grain size
measurements were carried out according to ASTM
E112-12.11 (Standard Test Methods for Determining Av-
erage Grain Size) using the intercept method. Interested
readers could refer to the standard document for detailed
test information.
Corrosion behavior was assessed in 0.1-M HCl solu-
tion (Fisher Scientific Company) using a potentiostatic
polarization device according to ASTM G31-72.12 stan-
dard procedure. A radiometer analytical model PGZ 100
Potentiostat/ Galvanostat with VoltaLab software was
used to analyze the corrosion results. A standard calomel
electrode was used as a reference and a platinum wire as
the counter-electrode. The treated specimens were used
as the working electrode. A scan rate of 1 mV/s starting
from 150 mV below to 50 mV above the testing cell in-
stant potential was operated to run the experiment. The
corrosion potential (E
corr
) and corrosion current density
(I
corr
) of each specimen were determined using the Tafel
plot method. All electrochemical experiments were per-
formed at 22±1 °C in 150 mL of solution.
3 RESULTS AND DISCUSSION
3.1 Effect of hardening temperature on the grain size
The effect of hardening temperature on the grain size
was studied and the results are presented in this section.
Figure 2 shows the microstructure of quenched and tem-
pered steels, taking into account the lowest and highest
temperatures for steel samples according to the informa-
tion in Figure 1. Similar microstructures for both tool
steels were reported by Roberts et al.
13
It could be seen
that the grain sizes of both AISI D2 and AISI O1 steels
decreased by increasing the hardening temperature. For
instance, the grain size of AISI D2 steel was reduced
gradually from 22.7 μm to 15.8 μm with a 50 °C incre-
mental increase in the hardening temperature. On the
other hand, the grain size of AISI O1 steel was reduced
S. AL-QAWABAH et al: EFFECT OF HEAT TREATMENT ON THE GRAIN SIZE, MICROHARDNESS ...
786 Materiali in tehnologije / Materials and technology 54 (2020) 6, 785–790
Table 1: Chemical composition of D2 and O1 alloy steels (w/%)
AISI C Si Mn Cr Mo V W Fe
D2 1.55 0.3 0.4 11.8 0.8 0.8
__ Bal.
O1 0.95
__
1.1 0.6
__
0.1 0.6
Bal.
Figure 1: Heat-treatment schemes of: a) AISI D2 tool steel and
b) AISI O1 tool steel

from 56.3 μm to 32.6 μm with a 30 °C incremental tem-
perature increase from 780 to 870 °C, respectively. The
calculated average grain sizes for AISI D2 and O1 steels
in the investigated temperature ranges are presented by
bar charts in Figure 3. The bar charts show a typical re-
lationship between the hardening temperature and the
grain size, i.e., the grain size decreases by increasing the
hardening temperature. This relationship is related to the
critical temperature of the steels, which is the so-called
austenitizing temperature.
The austenitizing temperature is the critical tempera-
ture necessary for the transformation in steel alloys to
take place after a long enough time. The fully auste-
nitized alloy can undergo a complete transformation
upon quenching to form the uniform hard martensite
structure shown in Figures 2b and 2d. On the other
hand, when alloys are heated below this critical tempera-
ture, an incomplete transformation may occur, which re-
sults in a non-uniform structure
14
as could be seen in
Figures 2a and 2c. For the investigated AISI D2 and O1
steels, the austenitizing temperatures are 1000°C and
820 °C, respectively
3.3 Grain size vs. microhardness relationship
The grain size is inversely proportional to the micro-
hardness number, as shown in Figure 4. The increase in
microhardness could be due to the high grain-boundary
density in the fine-grained structure.
15,16
The effect of
grain size on the material strength and hardness is known
as the grain-boundary strengthening mechanism 1 and is
defined by the Hall-Pitch 2 relationships as:
 y
=  0
+( k
y
* d
–0.5
)
H = H
0
+( k
H
* d
–0.5
)
where  y
is the yield stress, d is the average grain diam-
eter, o
, k
y
, H
o
and k
H
are material constants and H is the
hardness number. According to these equations, as the
grain size increases, yield strength  y
decreases, and
hardness decreases.
The microhardness could also be increased due to the
formation of the hard martensite structure. The finer
structure is known to have a complete martensitic trans-
formation. Both AISI D2 and O1 tool steels contain
other alloying elements than carbon, such as manganese
(Mn), chromium (Cr), and vanadium (V) as demon-
strated in Table 1, which are known as precipitate-form-
ing elements.
17
Therefore, a secondary hardening effect
can occur due to the segregation of the alloying elements
precipitates.
18
Table 2 summarizes the grain size and
microhardness of the AISI D2 and O1 tool steel as func-
tions of hardening temperature.
It can be concluded from Table 2 that the microhard-
ness is directly proportional to the hardening temperature
and inversely proportional to the grain size. In other
words, the highest microhardness was recorded for the
finer grain structure, which obtained at the highest hard-
ening temperature.
3.5 Corrosion properties
The influences of grain sizes on the corrosion behav-
ior of both AISI D2 and O1 tool steels were investigated
using potentiodynamic polarization curves. The typical
potentiodynamic polarization curves for the AISI D2 and
O1 steels, of different grain sizes, immersed in 0.1-M
HCl solution are presented in Figures 5a and 5b, respec-
tively. The corrosion rate in mm/year was calculated us-
ing Equation (1).
19
Corrosion rate (mm/year) = 3.28 x I
corr
x( M/n ) (1)
where M is the atomic weight of Fe (55.85 g), n is the
number of electrons transferred in the corrosion reaction
(n=2)and is the density (7.78 g/cm
3
for AISI D2 and
S. AL-QAWABAH et al: EFFECT OF HEAT TREATMENT ON THE GRAIN SIZE, MICROHARDNESS ...
Materiali in tehnologije / Materials and technology 54 (2020) 6, 785–790 787
Figure 2: Optical micrographs for heat-treated and tempered steels:
a) and b) for AISI D2 steel treated at 850 and 1000°C, respectively,
c) and d) for AISI O1 steel treated at 780 °C and 870 °C, respectively
Figure 4: Effect of grain size on the microhardness of: a) AISI D2 and
b) AISI O1 steel specimens
Figure 3: Effect of hardening temperature on grain sizes of: a) AISI
D2 and b) AISI O1 steel specimens

7.85 g/cm
3
for AISI O1). All I
corr
values were obtained
by extrapolating the Tafel regions.
20
The Tafel slopes for
the anodic and cathodic reactions can be obtained from
the linear regions of the polarization curve. Once these
slopes have been established, the anodic and cathodic re-
gions can be extrapolated back to the point where the an-
odic and cathodic reaction rates are equivalent. The cur-
rent density at that point is the corrosion current density
(I
corr
) and the potential at which it falls is the corrosion
potential (E
corr
).
21
Figures 6a and 6b show the corrosion current density
(I
corr
) and corrosion potential (E
corr
) of AISI D2 and O1
steels, respectively, which were obtained by the Tafel ex-
trapolation method. The electrochemical parameters,
E
corr
, I
corr,
and corrosion rate (in mm/Y) for both steels,
calculated from Figure 5, are summarized in Table 3.
The corrosion potential for AISI D2 in Figure 5a was in-
creasing with the increase in the hardening temperature.
The small variation in the corrosion rate of AISI D2
treated at 900 °C could be due to that the insignificant
difference in the grain size values with the samples
treated at 950 °C. Similarly, the corrosion potential was
increasing with temperature increase for AISI O1 steel
samples as well. In other words, the corrosion potential
of the fine-grained structures is higher than that of the
coarse-grained structures. The increased corrosion poten-
S. AL-QAWABAH et al: EFFECT OF HEAT TREATMENT ON THE GRAIN SIZE, MICROHARDNESS ...
788 Materiali in tehnologije / Materials and technology 54 (2020) 6, 785–790
Figure 6: Variation of experimental corrosion potential and corrosion
current density with grain size and temperature for: a) AISI D2 and b)
AISI O1 steels in 0.1-M HCl solution
Figure 5: Potentiodynamic polarization curves of: a) AISI D2 and b) AISI O1 tool steels in 0.1-M HCl solution
Table 2: Relationships between grain size and microhardness as functions of hardening temperatures for AISI D2 and O1 tools steels
Specimen No. AISI
Heat treatment regime
Average Grain Size
(μm)
Average Microhard-
ness (HV)
Hardening Tempera-
ture (°C)
Tempering Tempera-
ture (°C)
1
D2
850 540 22.7 475.0
2 900 540 18.9 590.0
3 950 540 17.0 610.0
4 1000 540 15.8 624.6
1
O1
780 450 56.3 340.0
2 810 450 46.0 403.0
3 840 450 38.0 491.1
4 870 450 32.6 520.6

tial suggests that fine-grained samples are more suscepti-
ble to corrosion. It can also be seen from Figure 5 and
Figure 6 that the I
corr
values increase when the grain size
decreases. The lower current density values indicate that
the corrosion rate (in mm/Y) is decreasing. This can be
attributed to the fact that making the grains finer renders
greater anodic areas than in the coarse grains and thus
leads to higher corrosion rates.
22
Corrosion rates of (7.06, 6.82, 7.88, and 19.77)
mm/year were obtained for AISI D2 samples treated at
(850, 900, 950, and 1000) °C, respectively. Whereas cor-
rosion rates of (10.15, 10.50, 13.06, and 14.35) mm/year
were obtained for AISI O1 samples treated at (780, 810,
840, and 870) °C, respectively. It can be concluded that
the computed corrosion rates were increasing with an in-
crease in the hardening temperature at which the grain
size was decreasing. This increase in the corrosion rate
implies that the corrosion resistance decreases when the
grain size decreases. Grain boundaries could be anodic
initiation sites for pit formation. However, since fine
microstructures have more initiation sites, more pits
would grow critical due to the presence of compensating
cathode area.
23
Table 3: Electrochemical parameters for the AISI D2 and O1 speci-
mens in 0.1 M HCl solution
D2
E
corr
(mV)
I
corr
(mA/cm
2
)
Corrosion rate
(mm/Y)
850 -679.8 0.60 7.06
900 -491.8 0.58 6.82
950 -429.5 0.67 7.88
1000 -290.4 1.68 19.77
O1
Ecorr
(mV)
Icorr
(mA/cm
2
)
Corrosion rate
(mm/Y)
780 -784.2 0.87 10.15
810 -783.1 0.91 10.50
840 -411.3 1.12 13.06
870 -342.3 1.23 14.35
It is noted from Table 3 that the AISI O1 steel is
more susceptible to corrosion in the HCl solution than
the AISI D2 steel. The improved corrosion resistance of
AISI D2 steel could be due to the presence of chromium
(Cr), molybdenum (Mo), and vanadium (V) alloying ele-
ments, which sacrifice corrosion for the iron. The corro-
sion of these alloying elements forms a protective layer
of reaction products on the martensite surface.
23
The
same effect was reported by Revie et al.
24
who stated that
the corrosion potential increases to the reference state
when more alloying elements are present due to the reac-
tion-product layer formation on the alloy’s surface dur-
ing corrosion. The corroded surfaces for the AISI D2 and
O1 steels treated at different temperatures are shown in
Figure 7.
It can be concluded from the surface examination that
the corrosion has taken place in all samples. However,
the corrosion effect was very obvious in the AISI O1
specimens. Furthermore, the depth and size of the pits in
the fine-grained material, in Figure 7b and 7d,w e r e
found to be larger than those in the coarse-grained sam-
ples in Figure 7a and 7c due to the presence of the com-
pensating cathode area in the dense gain-boundary areas.
5 CONCLUSIONS
The current study focused on the effect of the
heat-treatment regimes on the grain size, microhardness,
and corrosion behavior of AISI D2 and O1 tool steels. A
typical relationship between hardening temperature and
both grain size and microhardness number was obtained.
The fine-grained structures were obtained at high hard-
ening temperatures, because of complete martensite
transformation. Whereas at lower temperatures, an in-
complete transformation took place and coarse-grained
structures were obtained. The microhardness number in-
creased for the fine-grained structures due to the dense
grain-boundary areas and the presence of a hard
martensitic structure. The immersed AISI D2 specimens
in HCl showed better corrosion resistance than that of
AISI O1 due to the presence of high alloying elements,
which may help in forming a protective layer against
corrosion. The coarse-grained structures also showed
better corrosion resistance, because of the small
grain-boundary areas, which play a major role in initiat-
ing anodic sites for pit formation. Furthermore, the oxide
precipitates of other alloying elements accumulate in
grain-boundary areas, which could improve the corrosion
behavior of the studied steels.
S. AL-QAWABAH et al: EFFECT OF HEAT TREATMENT ON THE GRAIN SIZE, MICROHARDNESS ...
Materiali in tehnologije / Materials and technology 54 (2020) 6, 785–790 789
Figure 7: Micrographs of oil-quenched specimens for: a) and b) AISI
D2 treated at 850 °C and 1000 °C, respectively, c) and d) for AISI O1
treated at 780 °C and 870 °C, respectively

6 REFERENCES
1
W. Callister, D. Rethwisch, Materials Science and Engineering: an
introduction, NewYork, Wiley, 2007, doi:10.1016/0025-5416(87)
90343-0
2
N. Hansen, Hall–Petch relation and boundary strengthening, Scr.
Mater., 51 (2004), 801–806, doi:10.1016/j.scriptamat.2004.06.002
3
K. Ralston, N. Birbilis, Effect of grain size on corrosion: A review,
Corrosion, 66 (2010), 075005-075005–13, doi:10.5006/1.3462912
4
S. Krenk, Friction, dilation, and plastic flow potential, in: Physics of
Dry Granular Media, Springer Netherlands, Dordrecht, (1998),
255–260, doi:10.1007/978-94-017-2653-5_17
5
C. Obayi, R. Tolouei, A. Mostavan, C. Paternoster, S. Turgeon, A.
Okorie, D. O. Oray, M. Diego, Effect of grain sizes on mechanical
properties and biodegradation behavior of pure iron for cardiovascu-
lar stent application, Biomatter, 6 (2016), e959874, doi:10.4161/
21592527.2014.959874
6
G. Totten, L. Xie, K. Funatani, Handbook of Mechanical Alloy De-
sign, Marcel Dekker Inc., New York, NY, 2004
7
J. C. Díaz-Guillén, D. Guillén, G. Gutiérrez, González-Albarrán,
México C P, Electrochemical corrosion performance of AISI D2 tool
steel surface hardened by pulsed plasma nitriding, Int. J. Electro-
chem. Sci., 8 (2013), 973–982, www.electrochemsci.org
8
K. O. Orubite, N. C. Ngobiri, Corn silk as corrosion inhibitor for
mild steel in 0.1M HCl medium, IOSR J. Appl. Chem., 10 (2017),
51–60, doi:10.9790/5736-1003015160
9
C. Wei, F. Chen, Characterization on multi-layer fabricated by TRD
and plasma nitriding, Mater. Chem. Phys., 90 (2005), 178–184,
doi:10.1016/j.matchemphys.2004.10.008
10
N. Yasavol, H. Jafari, Microstructure, mechanical and corrosion
properties of friction stir-processed AISI D2 tool steel, J. Mater. Eng.
Perform, 24 (2015), 2151–2157, doi:10.1007/s11665-015-1484-3
11
ASTM E112-12, Standard Test Methods for Determining Average
Grain Size, in: B. Stand., Volume: 3, ASTM International, West
Conshohocken, PA, 2012
12
ASTM International, ASTM G31-72, Standard Practice for Labora-
tory Immersion Corrosion Testing of Metals, 2004
13
G. Roberts, G. Krauss, R. Kennedy, Tool Steels, 5th ed., ASM Inter-
national, Materials Park, Ohio, USA 1998, 1
14
H. Chandler, ed., Heat Treater’s Guide: Practices and Procedures for
Irons and Steels, 2nd ed., ASM International, Materials Park, Ohio,
USA, 1995
15
A. I. Zaid, A. O. Mostafa, Effect of hafnium addition on wear resis-
tance of zinc-aluminum 5 alloy: A three-dimensional presentation,
Adv. Mater. Lett.,8 (2017), 910–915, doi:10.5185/amlett.2017.1662
16
A. O. Mostafa, Mechanical properties, and wear behavior of alumi-
num grain refined by Ti and Ti+B, Int. J. Surf. Eng. Interdiscip. Ma-
ter. Sci., 7 (2019), 1–19, doi:10.4018/IJSEIMS.2019010101
17
J. Li, P. Zhao, J. Yanagimoto, S. Sugiyama, Y. Chen, Effects of heat
treatment on the microstructures and mechanical properties of a new
type of nitrogen-containing die steel, Int. J. Miner. Metall. Mater., 19
(2012), 511–517. doi:10.1007/s12613-012-0588-0
18
Y. Zhang, J. Li, C.-B. Shi, Y.-F. Qi, Q.-T. Zhu, Effect of heat treat-
ment on the microstructure and mechanical properties of nitrogen-al-
loyed high-Mn austenitic hot work die steel, Metals (Basel). 7
(2017), 94, doi:10.3390/met7030094
19
M. A. Amin, K. F. Khaled, S. A. Fadl-Allah, Testing validity of the
tafel extrapolation method for monitoring corrosion of cold rolled
steel in HCl solutions – Experimental and theoretical studies, Corros.
Sci., 52 (2010), 140–151, doi:10.1016/j.corsci.2009.08.055
20
G. S. Frankel, Fundamentals of corrosion kinetics, in: Act. Prot.
Coatings, (2016), 17–32. doi:10.1007/978-94-017-7540-3_2
21
D. G. Enos, L. L. Scribner, The Potentiodynamic Polarization Scan,
n.d. http://www.solartron.com (accessed August 12, 2019)
22
M. S. El-Sayed, A. H. Seikh, Effects of Grain Refinement on the
Corrosion Behaviour of Microalloyed Steel in Sulphuric Acid Solu-
tions, Int. J. Electrochem. Sci. 7 (2012) 7567–7578
23
T. Remmerswaal, The influence of microstructure on the corrosion
behavior of ferritic-martensitic steel, Delft University of Technology,
2015
24
R. W. Revie, H. H. Uhlig, Corrosion and corrosion control: An intro-
duction to corrosion Science and Engineering: Fourth Edition, 2008,
doi:10.1002/9780470277270
S. AL-QAWABAH et al: EFFECT OF HEAT TREATMENT ON THE GRAIN SIZE, MICROHARDNESS ...
790 Materiali in tehnologije / Materials and technology 54 (2020) 6, 785–790