Advances in Chemical Engi neering and Science , 20 1 1, 1, 51-60
doi:10.4236/aces.2011.12009 Published Online April 2011 (http://www.scirp.org/journal/aces)
Copyright © 2011 SciRes. ACES
The Corrosion Protection Behaviour of Zinc
Rich Epoxy Paint in 3% NaCl Solution
Nadia Hammouda1, Hacène Chadli2, Gil das Guillemot 3, Kamel Belmokre1
1 Laboratoire d’Anti corrosion Matériaux Enviro n nement, Université du 20 Août 1 955, Ski kd a, Al gérie
2Laboratoire de Métallurgie et Génie des Matériaux, Université de Bad ji Mokhtar, Annaba, Algérie
3Laboratoire de Méta llurgie Physique et Génie des Matériaux, Ecole Nationale
Supérieure d’Arts et Métiers de Lille, Lille Cedex, France
E-mail: hammoudanad@yaho o.fr
Received January 16, 2011; revised March 16, 2011; accept ed M ar ch 25, 2011
Abstract
Electrochemical impedance spectroscopy (EIS) in the l00 kHz - 10 mHz frequency range was employed as the
main electrochemical technique to study the corrosion protection behaviour of zinc rich epoxy paint in 3% NaCl
solution. The EIS results obtained at the open-circuit corrosion potential have been interpreted using a model
involving the impedance of particle to particle contact to account for the increasing resistance between zinc par-
ticles with immersion period, in addition to the impedance due to the zinc surface oxide layer and the electrical
resistivity of the binder. Galvanic current and dc potential measurements allowed us to conclude that the cathodic
protection effect of the paint takes some time to be achieved. The loss of cathodic protection is due to a double
effect: the decrease of the Zn/Fe area ratio due to Zn corrosion and the loss of electric contact between Zn to Zn
particles. Even when the cathodic protection effect by Zn dust become weak, the substrate steel is still protected
against corrosion due to the barrier nature of the ZRP film reinforced by Zn.
Keywords: Zinc-Rich Epoxy Paints, Cathodic Protection, Electrochemical Impedance Spectroscopy,
Corrosion Mechanisms
1. Introduction
The application of zinc-rich primers on ferrous substrates
is a very efficient method of anticorrosion protection.
They are used in many aggressive media: sea water, ma-
rine and industrial environments. It is a common fact that
in order to achieve a long-life coating system, a zinc
primer needs to be applied as the first coat. For sol-
vent-based zinc-rich paints (ZRPs), it seems to be estab-
lished that, at least at the beginning of immersion, zinc
particles provide a cathodic protection of the steel sub-
strate [1,2]. Then, a long term protection develops due to
the formation of zinc corrosion products, reinforcing the
barrier effect of the paint [1,3].
The metallic zinc content in the dry film is a very im-
portant parameter to be emphasized in the technical spe-
cifications of zinc-rich paints. However, as observed by
Lindquist et al., [4] this parameter is not the only factor
determining the performance of this kind of paint. For
exemple, Fragata [5] Del Amo [6] and Pereira [7] veri-
fied that the chemical nature of the binder and the zinc
particle size are also very important.
The zinc dust (spherical or lamellar shape, or a com-
bination of both) is dispersed in an inorganic (usually
orthosilicates) or organic binder (usually epoxies) [8].
These particles must be in electrical contact between
themselves and the metallic substrate in order to ensure a
well-established electrical conduction within the coating.
In such conditions of percolation, a galvanic coupling is
created between zinc and the substrate (steel) which is
nobler than the zinc. Then, zinc can preferentially dis-
solve, acting as a sacrificial pigment, and allowing a ca-
thodic protection of the substrate. Many studies [9-19]
exist in literature and relate the protection mechanisms
and degradation processes of such coatings.
Physico-chemical properties and corrosion resistance
of solvent-based zinc-rich paints ZRPs strongly depend
on pigment volume concentration (PVC), shape and size
of zinc dust [19,20]. In common liquid ZRP, zinc is usu-
ally introduced as spherical pigments with a mean
diameter ranging from 5 to 10 µm. To ensure good elec-
trical contacts between zinc pigments and the steel sub-
N. HAMMOUDA ET AL.
Copyright © 2011 SciRes. ACES
52
strate, a high pigment concentration is required (usually
above 60% by volume in solvent-based zinc-rich paints
ZRPs) [19]. A major drawback of classic solvent-based
paint is the emission of volatile organic compounds
(VOC), which contribute to atmospheric pollution. Since
the 1970 s, powder coatings are often preferred, because
they are composed of dry thermosetting powders (with-
out organic solvent) and more environmental abiding.
The aim of this work was to study the protective me-
chanisms of a single coat solvent-based zinc-rich paints
ZRPs. Primer coating panels were applied on sandblast-
ing steel and were studied when immersed in artificial
3% NaCl solution. The electrochemical behaviour was
studied using electrochemical impedance spectroscopy
(EIS) and by monitoring the free corrosion potential ver-
sus time. Raman spectroscopy was employed to explore
the oxidative state of zinc-rich paints after immersion
and to detect the zinc corrosion products, S.E.M. obser-
vations have also been employed to illustrate the non-
homogeneity of our paints.
The main objective is to propose a model of EIS re-
sults accounting for the zinc particles distribution and
mechanisms of water entrance within the coating.
2. Experimental Part
2.1. Sample Material and Preparation
The metallic substrate was A283C steel (according to
NF10027 standard) in conformity with the norm API
(American Petroleum Industry), used in the storage res-
ervoirs of the Algerian crude oil, the chemical composi-
tion of the tested steel is given in Table 1. Before coat-
ing application, the metallic substrate was sandblasted to
Sa 2.5 (Swedish Standard SIS 05 59 00/67) (roughness
Ra 6.2 µm) or polished with emery paper up to G 400.
Commercial epoxy-ZRPs were immediately applied onto
steel panels using a brush or a roller (Figure 1). Once
cured, the samples were stocked in a desiccator until the
moment of testing. The coating thickness was measured
using an Elcometer gauge and was found around 80 µm
for all panels, the composition of the coating is proprie-
tary information.
Coated panels were cut out (100 cm × 60 cm × 4 cm)
and an electrical wire was added in order to allow elec-
trochemical measurements. With the aim to achieve the
electrochemical measures in the best conditions it has
been suited that the areas of about 15 cm2 exposed to the
electrolytic solution were sufficient. It seemed necessary
to use a surface of paint relatively big in contact with
electrolytic solution in order to compensate the insulating
role of the sample as the thickness of the film grows.
Mansfeld reports in a technical document [21] a study of
Table 1. Chemical composition of A283C steel (% in weight).
C Mn S P Cu Si
0.24 0.9 0.04 0.035 0.2 0.4
(a)
(b)
Figure 1. Cross-section of the studied ZRP. (a) Prior to ex-
position. The observed white particles are due to the sphe-
rical zinc particles. (b) After 360 days of immersion in NaCl
3%. Substrate steel is seen as the white region at the top of
micrography.
Kendig and Scully suggesting the use of samples covered
with a ratio area/thickness of the coating of at least 104 to
assure satisfactory electrochemical measurement.
Samples were exposed under open circuit potential
conditions in NaCl aqueous solution normally aired and
none agitated whose concentration is 30 g/l for electro-
chemical impedance.
2.2. Electrochemical Impedance Spectroscopy
Measurements
The Electrochemical Impedance Spectroscopy (EIS)
measurement is carried out in a 3% NaCl solution, using
a potentiostat/galvanostat EG&G A273. A frequency re-
sponse analyser Solartron FRA 1260 connected to an
N. HAMMOUDA ET AL.
Copyright © 2011 SciRes. ACES
53
electrochemical interface Solartron SI 1287 was used to
perform EIS measurements. A filter (Kemo VBF 8) was
also employed to improve the signal to noise ratio. The
frequency domain covered was 100 kHz to 10 mHz with
the frequency values spaced logarithmically (five per
decade). The width of the sinusoidal voltage signal ap-
plied to the system was 10 mV. All the measurements
were performed at the open circuit potential and at dif-
ferent immersion times. The electrolyte was confined in
a glass tube which was fixed to the painted surface by an
O-shaped ring. The total tested area was 15 cm2. Plati-
num gauze of large area was used as a counter electrode.
All the potentials in the current article are referred to
saturated calomel electrode (SCE). During the intervals
between EIS measurements, the painted specimen was
kept in the electrolyte cell without reference electrode.
The cell design for EIS measurement was described in
detail in a previous work [22].
2.3. Characterization of Wash Primer Coatings
2.3.1. FTIR An al ysi s
The FTIR spectra of zinc rich epoxy paint were taken
with SHIMATZU 8000 série + FTIR Spectrometer using
ATR attachment in the range 4000 - 450 cm1.
2.3.2. Micro-Raman Spectroscopy
Cross sections of the zinc-rich epoxy paint were polished
and analyzed ex situ by micro-Raman spectroscopy after
immersion. Fresh polishing with 1 µm diamond paste
was performed just before Raman analysis. Figure 2
shows cross-section obtained by scanning electron mi-
croscopy of the ZRP. Only zinc particles (spherical) are
observable. This figure shows that the distribution of the
spherical pigments is quite inhomogeneous while zinc
plates are uniformly distributed. Raman spectropho-
tometer (Labram from Jobin Yvon with an optical mi-
croscope from Horiba) was equipped with a HeNe laser
(632.81 nm); the output power was 0.97 mW at the sam-
ple. A confocal hole set at 200 µm allowed an analyzed
depth lower than 10 µm on transparent products. A 80
ULWD objective from Olympus was used to select the
analyzed area. Raman spectra were only acquired on
spherical zinc particle frontier.
3. Results and Discussion
3.1. Electrochemical Properties of Sandblasted
Steel (1
Sa2 2)
To the analysis of the curves (Figure 3), we note a con-
tinuous deterioration of the sandblasted steel to Sa 2.5
Figure 2. Cross section SEM micrography of the coating
wherespherical zinc particle is visible.
050100 150 200
0
20
40
60
80
100
120
140
Z''(ohm)
Z'(oh m)
0 h
2 d
4 d
7 d
8 d
9 d
11 d
14 d
15 d
18 d
22 d
Figure 3. Evolution of Nyquist diagrams as a function of
immersion time in 3% NaCl solution for the sandblasted
steel (Sa 2.5).
provoking a change in the state of the metallic surface. It
can for example, to cover of corrosion products, weakly
adhesive which provoke a stability of the free corrosion
potential, the value was around –0.684 V/SCE. The dia-
grams of Nyquist determined to different time of immer-
sion, in the 3% NaCl solution normally aired and non
agitated are represented on the Figure 3, the values of
the different parameters are gathered in the Table 2.
The values of the electrolyte resistance Re are very
weak, of the order of 14 ·cm2, what shows that the
middle is very conductive.
To the analysis of the impedance diagrams, since the
first hours of immersion of the metallic substrate, we
register a rapid evolution of the charge transfer resistance
Rct of the sandblasted steel, we note that at the beginning
of the immersion the value of the charge transfer resis-
tance Rct only makes increase until to the fourth days of
N. HAMMOUDA ET AL.
Copyright © 2011 SciRes. ACES
54
Table 2. Parameters values extracted from the fitting pro-
cedure.
Time (days) Re (·cm2) Rct (K·cm2) Cdl (mF/cm2)
0 h 17.97 1.044 3.810
2 13.53 3.804 4.183
4 13.14 3.532 4.505
7 13.77 2.201 2.892
8 14.53 4.460 3.568
9 14.51 5.877 2.707
11 13.65 1.706 2.331
14 14.67 2.991 2.218
15 14.95 5.532 2.876
18 14.28 2.597 2.450
22 16.02 2.546 2.500
immersion (96 hours), it means that the process govern-
ing the kinetics is under control of load transfer. Ac-
cording to the Figure 4 we notes that the charge transfer
resistance Rct evolves cyclically with time of immersion
(growth then decrease) this state of fact to been signalled
already by certain author [23,24].
The tracing of the double layer capacitance Cdl curve
as a function of exposure time from the values arranged
in the Figure 4, show an increase of the capacity of dou-
ble layer Cdl since the first hours of exposure. This
growth is more or less important (3.810 to 4.505 mF·cm–2)
translating the deterioration of steel thus, but beyond the
seventh day (168 hours) of immersion it decreases sud-
denly (2.892 mF·cm–2), we think that the slowing of the
decrease of the double layer capacitance Cdl would be
due to the formation of corrosion products (Figure 4)
forming a film more or less adhesive to the substrat
playing the role of a gate, beyond 216 hours the capacity
of double layer fluctuates weakly that we can consider
like steady.
This situation has already been met, at the time of our
survey with the different states of naked surface. This
phenomenon observed by Duprat [25], has been assigned
to the porous nature of corrosion products formed at the
free corrosion potential and present at the metallic inter-
face (Figure 5).
The model of equivalent circuit proposed and pre-
sented in Figure 6 could be used to represent the elec-
trochemical behaviour of our samples after immersion in
3% NaCl solution, in this circuit Re is the resistance of
electrolyte (·cm2), Rct the charge transfer resistance
(.cm2) Cdl the double layer capacitance (F·cm–2).
3.2. EIS Behavior of Zinc Rich Epoxy Paint
Zinc-rich primers can only protect the steel cathodically
when the zinc particles in the primer have electric con-
tact to the steel substrate. Only the zinc particles in direct
contact with the steel substrate, or connected through
Figure 4. Variation of Rct and Cdl with time of exposure.
Figure 5. Cross section SEM micrograph on sandblasted
steel (Sa 2.5).
Figure 6. Equivalent circ uit used to model sandblasted steel
(Sa 2.5) during immersion in 3% NaCl solution.
N. HAMMOUDA ET AL.
Copyright © 2011 SciRes. ACES
55
other zinc particles, will contribute to the cathodic pro-
tection. It is therefore necessary to have a large amount
of zinc dust in the coating.
The potential of ZRP is approximately 1.160 V/SCE,
while the steel substrate used here has a potential of ap-
proximately 0.65 V/SCE. The measured potentials are
mixed potentials between the steel substrate and the “ac-
tive” zinc-pigments, and will depend on the area ratio
between the two. If only few zinc-pigments are active,
the anode area will be small, and the potential will be
close to that of the steel. On the other hand, if the area of
active zinc particles is large, the potential will be close to
that of zinc.
The Nyquist impedance diagrams for the ZRP coated
panels obtained in the aerated 3% NaCl solution as a
function of immersion time are shown in Figure 7(a).
Two time constants (two loops) were clearly defined at
the beginning of the exposure, that become more and
more distinct as the immersion time increases, which
corresponds well with the model shown in Figure 10 one
in the high frequency range (Figure 7(b)) which is re-
lated to the coating properties followed by a second one
at lower frequencies which is related to the corrosion
process [26,27]. At high frequencies, the impedance re-
duces to one or two semicircles with diameters of charge
transfer resistance and pore resistance. At lower frequen-
cies, a Warburg impedance develops on the Nyquist plot
by a straight line superimposed at 45˚ to both axes,
which shows a shielding effect on mass transport of re-
actants and products. The shape of the impedance plot
suggests that the ZRP corrosion changes from charge
transfer control process to diffusion control process dur-
ing time of immersion.
By considering the morphology and the EIS of the
ZRP, the impedance first decreased for few days show-
ing the zinc particles activation before an increase related
to the zinc corrosion products formation.
The fitting of EIS data was performed by Zview soft-
ware (Scribners Associates, USA) using different elec-
trical equivalent circuits which include two time con-
stants [28,29].
Another difference with previous studies on ZRPs was
found in the visual observation of panels during immer-
sion. Usually, zinc corrosion products are clearly ob-
served as white scale at the ZRP panel surfaces [30]
(Figure 8(a)). These new products would be maintained
within the coating at the neighbourhood of the corroded
zinc particles. Moreover, they could also contribute to
the isolation of zinc particles as a protective barrier
which reduces the corrosion rate of zinc and the coating
porosity. Figure 8(b) shows the visual appearance of
zinc rich epoxy paint coated panel after 180 days (six
months) of immersion where the whiteness related to the
zinc corrosion products was not observed. It means that
(a)
050100 150 200 250 300
0
50
100
150
200
Z'' ( ohm)
Z'(ohm)
(b)
Figure 7. Electrochemical impedance spectroscopy dia-
grams for ZRP as a function of immersion time in aerated
3% NaCl solution.
(a) (b)
Figure 8. Visual aspect of zinc rich epoxy paint after six
months of immersion in 3% NaCl solution.
after zinc corroded, zinc corrosion products were not
able to reach the coating/electrolyte interface, the surface
appears damaged with the presence of the red rust due to
a progressive attack informing on the state of steel sub-
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Copyright © 2011 SciRes. ACES
56
strat, at this stage of deterioration, the coating lost all its
protective properties.
3.2.1. Ecor Evolution
According to Abreu et al. [2], the evolution of the free
corrosion potential Ecor allows to follow the electro-
chemical activity of the ZRP. It is believed that the elec-
trochemical processes occurring in such systems are the
oxidation of zinc particles (2
Zn Zn2
è) and the
reduction of dissolved oxygen (22
O2HO4é
4OH). The authors reported that the Ecor evolution for
liquid ZRP coated samples is in close relationship with
the ratio of active areas (zinc/steel) and allows to define
the cathodic protection (CP) duration which is the period
where Ecor remains lower than 0.86 V/SCE, a value
corresponding to the commonly accepted criterion of a
maximum Fe2+ concentration of 10–6 M. In other words,
the increase in this potential corresponds to the decrease
of the electroactive zinc area which means the decrease
of the cathodic protection intensity. This is generally
attributed to the isolation of the zinc particles by the zinc
corrosion products in the coating.
Figure 9 shows the Ecor evolution with time of coated
steel substrates with Zinc rich epoxy paint. It can be seen
that Ecor was cathodic between 1.0 and 0.8 VSCE during
the six months of entire immersion, this result could be
due to a high zinc particles amount. This shows that the
zinc particles in the primers were electrochemically ac-
tive with a high number of electrical contacts between
zinc particles. This high percolation means that zinc
pigments improve a good electrical contact which im-
plies that the steel substrate was under a good CP. That
means that a higher part of the zinc particles was in-
volved in a percolation process.
However, as the CP duration is due to the activation of
zinc particles by the electrolyte penetration, it also means
that the zinc dissolution is reduced or that galvanic con-
tact was lost after six months of immersion in 3% NaCl
solution, some small spots of iron rust are detected on the
film surface, indicating that the iron corrosion process
started some days before. For our zinc-rich primers, it
has been observed that zinc corrosion products precipi-
tate inside the coating, around the zinc particles that
originated them, blocking the pores of the coating and
therefore increasing its barrier resistance [31]. After the
test the latter sample was covered with red rust in a lim-
ited area. Probably the primer was very thin there, so that
the zinc particles were consumed and the steel started to
corrode.
3.2.2. Equivalent Circuit for the EIS Simulation
The electrical circuits that are used to simulate the EIS
results are shown in Figure 10. By considering the mor-
E
cor
(mV/ECS)
Figure 9. Variations in corrosion potential with time for
ZRP exposed in 3% NaCl solution at ambient temperature.
phology and the EIS of the ZRP, the corrosion process
and its equivalent circuit are proposed. At the beginning
of the immersion, the model circuit was proposed by the
combination of Randles type equivalent circuits for a
porous paint film [32] and an intact paint film [33], as
shown in Figure 10(a).
In the case of Figure 10(a), the nature of the zinc rich
epoxy paint enables the coating to be modelled as an
ideal capacitance Cf in parallel with the ionic resistance
Rf through the coating. In Figure 10, electrical circuits
used to simulate the EIS results.
In the same way the presence of a metal surface with-
out chemical pretreatment together with the iron electro-
chemical dissolution reaction which involves a single
time constant, enables the metal-paint interface to be
considered as a resistance (the charge transfer resistance
Rct) in parallel with the double layer capacitance Cdl (the
double layer capacitance on quite a rough surface). In
this example the suggested model is simple but it is in
good agreement with the experimental result (Figure
10(b)). Moreover, after about 180 days of immersion we
can observe the appearance of a diffusion tail at the low-
est frequencies (Figure 10(c)). In most of the cases, a
circuit including diffusion impedance through a layer of
finite thickness [2] gave the best agreement between ex-
perimental and calculated curves. This circuit describes a
degraded coating with a weak charge transfer [34].
3.3. Micro-Raman Spectroscopy
In order to understand the behaviour of zinc rich epoxy
paint, complementary analyzes were carried out. Raman
spectroscopy analyzes were performed after 180 days (6
months) of immersion of the zinc rich epoxy paint. This
technique allows to identify locally zinc corrosion prod-
ucts inside the coatings. Representative spectra obtained
N. HAMMOUDA ET AL.
Copyright © 2011 SciRes. ACES
57
(a) (b)
(c)
Figure 10. Electrical circuits used to simulate the EIS re-
sults.
for our sample are shown in Figures 11(a) and (b). In
Figure 11(a), a characteristic peak was observed at
543 cm–1 which was attributed to a non-stoichiometric
oxide Zn1+xO [35,36], which is detected on some parti-
cles of zinc to some micrometers of the electrolyte/
coating interface whereas only the metallic zinc is de-
tected on the other particles. This shape of the non-stoi-
chiometric zinc oxide Zn1+xO, where zinc ion is in inter-
stitial position had been observed by Tzolov and alli [37].
Other corrosion products were detected inside the
coatings and their characteristic wavenumbers (Figure
11(b)). We detected additional peaks at 240.5, 392.2 and
409.7 cm–1 attributed to simonkolleϊte [4Zn (OH)2·Zn Cl2·
H2O] a kind of zinc corrosion products, we detected also
additional peak at 1340 cm–1. The oxidized forms were
first observed at the solution/coating interface and pro-
gressed towards the steel substrate as the immersion du-
ration increased.
3.4. FTIR Spectral Characterization
The FTIR spectrum of the zinc rich epoxy paint is shown
in Figure 12. The peaks around 850 cm1, 1250 cm1,
1510 cm1, 1600 cm1 and 1460 cm1 are due to the resin
epoxy. The film is found to be hydrated by the presence
of peak at 3400 cm1 due to O–H absorption band.
From FTIR spectra result, it can be concluded that the
synthesised zinc rich epoxy paint was under a conductive
form, which is represented in the Figure 13.
3.5. SEM Analysis
Cross section S.E.M. micrographs of several ZRP sam-
ples exposed to the electrolyte for different time are
shown in Figure 14. It was clearly observed that the
coating presented zones which did not contain zinc parti-
cles. Moreover, it can be seen that the zinc particle shape
varied significantly from spherical to elongated forms.
Most of the zinc particles were not in direct contact with
Figure 11. Raman spectrum of zinc particles near the in-
terface film/electrolyte after six months of immersion in 3%
NaCl solution.
Figure 12. FTIR spectra of zinc rich epoxy paint (ZRP).
the substrate. These observations about the zinc particles
distribution were considered to analyse EIS spectra.
Figures 14(a) and (b) represents a testing panel cov-
ered with the oxidation products after exposure to 3%
NaCl solution. The oxidation of zinc in the coating cre-
ates the so-called “white corrosion”; the shapes of dam-
age were under Cracks and scaling damage. Sealing of
pores in a spherical zinc-pigmented coating. Which is
necessary to secure the barrier protection of the substrate.
The scheme outlines the possible reactions at the ap-
pearance of oxidation zinc products; these products are
of alkaline nature and can manifest themselves in the
neutralization protection mechanism [38,39].
4. Conclusions
Solvent-based zinc-rich paints (ZRPs) was characterised
using EIS after immersion in 3% NaCl solution. EIS was
found to be a useful tool for assessing the protective be-
N. HAMMOUDA ET AL.
Copyright © 2011 SciRes. ACES
58
O
H
2
CCHCH
2
O
C
HCH
2
OC
CH
3
CH
3
OCH
2
CHCH
2
OH
C
CH
3
CH
3
OCH
2
O
n
Hydroxyle Oxiranne
Figure 13. Structural formula of the zinc rich epoxy paint.
(a) (b)
Figure 14. SEM pictures of zinc rich epoxy paint in 3% NaCl solution.
havior of ZRPs organic coatings, after immersion, the
EIS diagrams showed clearly two capacitive loops. How-
ever, classical equivalent circuits used to monitor coating
degradation were unable to provide satisfying fitting re-
sults. Results clearly demonstrate that the galvanic pro-
tection stage requires good electrical contact among the
zinc particles. In samples with a Zn content higher than
80%, the cathodic protection effect was steel in action
after about 180 days of immersion in 3% NaCl solution.
The good performance of ZRP coatings during im-
mersion can also be explained by the retention of zinc
corrosion products into the coating which allow improv-
ing barrier properties. However, it is important to re-
member that the zinc-rich paint effectiveness does not
depend solely on electrochemical factors.
There are other factors such as mechanical properties
(cohesion, adhesion to Sa 2.5, flexibility, etc) that are
very important. So, the addition of auxiliary pigments
should be controlled carefully in order not to impair the
film’s physical and chemical characteristics. These re-
sults highlight that powder zinc-rich coatings are com-
plex systems.
5. Acknowledgements
Thanks are due to Sonatrach (Direction Régionale de
Skikda, Algeria) for providing ZRP coated panels.
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