N. ZAZI et al.: CORROSION BEHAVIOR AND THE WEAK-MAGNETIC-FIELD EFFECT OF ALUMINUM ...
165–173
CORROSION BEHAVIOR AND THE WEAK-MAGNETIC-FIELD
EFFECT OF ALUMINUM PACKAGING PAPER
VPLIV [IBKEGA MAGNETNEGA POLJA NA KOROZIJO
ALUMINIJEVE EMBALA@NE FOLIJE
Nacer Zazi1, Jean-Paul Chopart2, Ali Bilek1
1University Mouloud Mammeri of Tizi-Ouzou, Faculty of Construction Engineering, Department of Mechanical Engineering (LMSE),
B.P.17 RP Tizi-Ouzou, Algeria
2Université de Reims Champagne Ardenne, LISM EA 4695 UFR SEN, BP1039, Moulin de la Housse, 51687 Reims, Cedex, France
zazinacer@yahoo.fr
Prejem rokopisa – received: 2014-05-21; sprejem za objavo – accepted for publication: 2015-04-13
doi:10.17222/mit.2014.083
Aluminum can be absorbed through the digestive system from water and drinks and the food that contains natural traces and
processed food or the food cooked in aluminum cookware. Some studies show that the people exposed to high levels of
aluminum may develop kidney, bone and brain diseases. Aluminum foil (AlFeSi) is daily used as packaging for food and drugs
stored in the refrigerator where an electric motor induces a magnetic field of a few microteslas. The purpose of this work is to
study the corrosion behavior of various aluminum packaging foils and the effect of a weak magnetic field on the morphology
and the corrosion kinetics in the 0.3 % and 3 % of mass fractions of NaCl solutions. The mean results for various aluminum
packaging foils show that localized corrosion is controlled by the electrochemical potentials of different phases constituting the
aluminum foil and the concentration of the precipitates from the other phases. The morphology and the corrosion kinetics of
aluminum packaging foil in the 0.3 % and 3 % of mass fractions of NaCl solutions are different with and without an application
of a weak magnetic field. Electrochemical tests applied to cheese packaging paper show that the introduction of a magnetic field
decreases the polarization resistance, the potential of passivation and the value of the open-circuit potential at the beginning of
the corrosion; however, its passivation-current density increases at the beginning of the corrosion. The values of the open-circuit
potential with and without a weak magnetic field are the same after thirty days of corrosion.
Keywords: aluminum packaging foil, weak magnetic field, aluminum alloys, corrosion, passivation
Aluminij se lahko absorbira v prebavni sistem iz vode in pija~ in iz hrane, ki vsebuje naravne sledi ter obdelane hrane ali hrane,
kuhane v aluminijasti posodi. Nekatere {tudije ka`ejo, da ljudje izpostavljeni visokemu nivoju aluminija, lahko zbolijo na
ledvicah, kosteh in mo`ganih. Aluminijeva folija (AlFeSi), ki se dnevno uporablja kot embala`a za hrano in zdravila, se hrani v
hladilniku, kjer elektromotor inducira magnetno polje jakosti nekaj mikroteslov. Namen {tudije je predstavitev korozijskega
obna{anja razli~nih aluminijevih embala`nih folij in vpliv {ibkega magnetnega polja na morfologijo in kinetiko korozije v 0,3 %
in 3 % raztopini NaCl. Rezultati ka`ejo, da je pri razli~nih aluminijevih folijah lokalna korozija kontrolirana z elektrokemijskim
potencialom razli~nih faz, ki sestavljajo aluminijevo folijo in s koncentracijo izlo~kov drugih faz. Morfologija in kinetika koro-
zije aluminijevih embala`nih folij v 0,3 % in 3 % raztopini NaCl, sta razli~ni pri prisotnosti ali odsotnosti {ibkega magnetnega
polja. Elektrokemijski preizkusi, izvr{eni na ovojni foliji za sir, so pokazali, da prisotnost magnetnega polja na za~etku korozije
zmanj{a polarizacijsko odpornost, potencial pasivacije in vrednost potenciala odprtega kroga, vendar pa gostota pasivacijskega
toka nara{~a. Vrednost potenciala odprtega kroga je po tridesetih dneh enaka, ob prisotnosti ali odsotnosti {ibkega magnetnega
polja.
Klju~ne besede: aluminijeva embala`na folija, {ibko magnetno polje, aluminijeve zlitine, korozija, pasivacija
1 INTRODUCTION
Aluminums, when combined with various elements
and subjected to various thermomechanical treatments,
exhibit considerable advantages, such as good mecha-
nical properties. However, the use of these alloys does
not remove any disadvantage; for example, various types
of corrosion can appear. These alloys are used as packag-
ing for foodstuffs, drugs, and in the kitchen utensils for
short, average or long durations because of their low
density, good formability and excellent corrosion resis-
tance in the air environment.1–3 The corrosion resistance
of aluminum is directly related to the formation of an
alumina oxide or hydroxide on the material surface,
inducing a relative passivation of these alloys. This resis-
tance is limited to the environments where these oxides
are slightly soluble at the pH values of 4–9.1
Aluminum alloys are sensitive to localized corrosion
in aggressive environments containing chlorides such as
food and drugs. Several theories on localized corrosion
were closely connected to the passive oxide-film rupture.
In aluminums, localized corrosion appears when
aggressive ions such as chlorides break the protection by
locally attacking the passive layer. The chlorides
generate the corrosion surrounding the defect oxide film
in surface heterogeneities, such as crevices, precipitates
and intermetallic particles.4–8 These heterogeneities
create a distribution of cathodic and anodic areas across
the alloy surface and then various forms of localized
corrosion take place.5
Aluminum of the first fusion contains 0.1 % iron,
which is higher than the limit solubility of iron in
aluminum at room temperature. Moreover, only few
products are elaborated from aluminum of the first
Materiali in tehnologije / Materials and technology 50 (2016) 2, 165–173 165
UDK 669.717:620.193:544.6 ISSN 1580-2949
Original scientific article/Izvirni znanstveni ~lanek MTAEC9, 50(2)165(2016)
fusion, while great quantities of recycled-aluminum
alloys are used in the manufactured products. This
increases the iron content in aluminum alloys, so iron
phases are formed.9
An iron phase is cathodic and nobler than aluminum;
its presence in an aluminum alloy affects the kinetics of
the aluminum anodic dissolution and makes it a signifi-
cant factor of the localized aluminum-alloy corrosion.9
The richer the phases are in iron, the more they become
favorable sites for cathodic reactions and their surround-
ings are adequate positions for anodic reactions and
localized corrosion.
Others impurities are soluble in aluminum because
their solubility limits are higher than their concentrations
in aluminum.
The presence of different intermetallic precipitates in
aluminum-matrix alloys increases the mechanical pro-
perties and their susceptibility to corrosion.10
Aluminum alloys used for kitchen utensils come
from recycled worn parts of cars, aircraft, gutters, wires,
drink cans, etc. Their chemical analysis revealed the
presence of heavy elements such as Cd, Co, Cr, Pb, Ni
and Zn. These utensils can contaminate man’s food chain
and lead to a bio-accumulation of heavy metals in the
vital parts of the human body such as liver, kidneys,
spleen.11–12 When the concentration of these elements is
higher than their solubility limit, they modify the electro-
chemical potential of the material surface by generating
new intermetallic particles or joining the chemical com-
positions of the existing intermetallic particles.
Magnetic fields are powerful scientific tools for
metal-deposition or dissolution studies. The presence of
a magnetic field improves the mass transfer of an elec-
trochemical system, the quality of the deposit and the
influence of the corrosion phenomena.13
Aluminum foil is daily used as packaging for food
and drugs stored in a refrigerator where an electric motor
induces a magnetic field of a few microteslas.14
The purpose of this study is to examine the corrosion
phenomena of various aluminum foils intended for food
and drug packaging and aluminum kinetic dissolution.
The effect of a week permanent magnetic field on the
morphology and corrosion kinetics of an aluminum foil
in a NaCl solution is also examined.
2 MATERIALS AND METHODS
Various aluminum packaging foils were tested in our
experiments using light microscopy, scanning electronic
microscopy, X-ray diffraction and corrosion tests.
Batches of aluminum foil intended for cheese, chocolate,
drug and foodstuff packaging in rolls were used as
samples.
The nominal chemical composition of different alu-
minum packaging paper is given in Table 1.
The corrosion measurements were undertaken at
room temperature. Samples of 1 cm2 (Ø = 11.28 mm)
were immersed in chloride sodium solutions of the 0.3 %
and 3 % of mass fractions of NaCl. The four-electrode
method was used. A saturated calomel electrode (SCE)
was used as the reference electrode. The two auxiliary
electrodes were in graphite.
Open-circuit potential and current potential were
obtained by means of an EGG-Princeton 263 poten-
tiostat. Before determining the layout of the polarization
curves, the working electrode was polarized at –0.8 V. To
obtain the polarization curves, we applied a potential that
evolved to ascending values, passing from the cathodic
domain towards the anodic domain. The samples in-
tended for electrochemical tests, microscopic examina-
tion and X-ray diffraction were not polished in order to
keep the surface of the aluminum foil appropriate for its
daily use.
The microstructures and surface morphologies of
corroded and non-corroded samples were characterized
with light microscopy and scanning electron microscopy
(Philips Esem-XL30, tungsten filament). Prior to
microscopic characterization, the corroded samples were
rinsed with distilled water and dried in desiccators.
The chemical composition of the aluminum foil sur-
face was characterized with a JEOL JSM 6460LA micro-
scope coupled with an EDS JEL 1300 microprobe.
The corrosion tests were carried out by immersing
the aluminum packaging-foil samples in the 0.3 % and
3 % of mass fractions of NaCl solutions at pH = 7 with
and without a week permanent magnetic field (42 mT).
A magnet with a ring shape was positioned near the
sample surfaces. The same distance was kept between
the working electrodes and the magnet for all samples.
Micro-hardness measurements were taken with a
Zwick Roell ZHV 1M tester. The HV scale, under a load
of 5 g was chosen for this testing. Five measurements
were taken for each sample.
N. ZAZI et al.: CORROSION BEHAVIOR AND THE WEAK-MAGNETIC-FIELD EFFECT OF ALUMINUM ...
166 Materiali in tehnologije / Materials and technology 50 (2016) 2, 165–173
Table 1: Chemical compositions of various packaging foils
Tabela 1: Kemijska sestava razli~nih embala`nih folij
Elements/Aluminum
packaging foil for: Al Si Fe Mg Cu Mn V Cr Ti Zn Other
domestic use 99.344 0.208 0.253 0.040 0.038 0.035 0.020 0.012 0.006 0.004 0.040
drug 98.100 0.700 0.820 0.050 0.095 0.014 0.020 0.022 0.050 0.086 0.043
chocolate 99.271 0.300 0.150 0.035 0.025 0.022 0.033 0.005 0.040 0.026 0.093
cheese 98.300 0.630 0.575 0.083 0.072 0.026 0.011 0.016 0.042 0.076 0.169
The X-ray spectrum was obtained with a Bruker AXS
D8 Advance diffractometer.
3 RESULTS AND DISCUSSION
The Vickers micro-hardness results obtained for
several batches of aluminum packaging foil for cheese
(Table 2) show the changes between the batches. This
means that the mechanical and chemical properties of the
aluminum foil surface change from one batch to
another.7,15 Consequently, the morphology and corrosion
kinetics are expected to differ from one batch to
another.7,15
Table 2: Hardness measurements of aluminum packaging foils
Tabela 2: Meritve trdote aluminijevih embala`nih folij
Sample of the cheese
aluminum packaging foil 1 2 3
Vickers micro-hardness
(25 °C) 16.2 19.4 14.8
The aluminum packaging foil under light and
scanning electron microscopy reveals an aluminum
solid-solution matrix, intermetallic particles and or preci-
pitates (Figures 1 to 3). The microstructure of a
non-polished aluminum drug-packaging foil shows the
presence of furrows oriented in one direction (Figure
1d). Except for certain batches of aluminum cheese-
packaging foil, no furrows were observed (Figures 1a to
1c). This is probably due to the wear of the rolling mills
during the manufacture of aluminum cheese-packaging
foil. The furrows on the surface constitute corrosive-
solution storage zones that induce differential aeration.
This phenomenon causes changes in the morphology and
the kinetics of corrosion and increases the dissolution of
aluminum and other anodic metals. Several precipitates
were seen in the aluminum drug-packaging foil (Figure
2).
The thermomechanical history varies between
different aluminum foils. On the surface perpendicular to
a rolled surface, the grains appear to be small for all the
aluminum foils (Figure 3). The aluminum packaging
foils do not have the same thickness and the same grain
size (Figure 3). The X-ray spectrum of the aluminum
packaging foil intended for drugs (Figure 4) and the
texture-calculating method of Muresan et al.16 show the
presence of a pseudo-texture because the rates of the
(220 and 311) plans exceed 50 %. This is probably due
to the mechanical treatments (cold rolling) during its
elaboration. This can influence the corrosion phenomena
and support an oriented corrosion with privileged plans.
N. ZAZI et al.: CORROSION BEHAVIOR AND THE WEAK-MAGNETIC-FIELD EFFECT OF ALUMINUM ...
Materiali in tehnologije / Materials and technology 50 (2016) 2, 165–173 167
Figure 3: Perpendicular face of rolled aluminum foil for: a) domestic
use, b) chocolate, c) cheese and d) drugs
Slika 3: Pre~ni presek valjane aluminijeve embala`ne folije za: a)
gospodinjstvo, b) ~okolado, c) sir in d) zdravila
Figure 1: Microstructure of the aluminum packaging foil: a) for
domestic use, b) for chocolate, c) for cheese, d) for drugs
Slika 1: Mikrostruktura aluminijeve folije: a) za gospodinjstvo, b) za
~okolado, c) za sir, d) za zdravila
Figure 2: Micrographs of scanning electron microscopy (SEM) show-
ing the structure of aluminum: a) for domestic use, b) for chocolate, c)
for cheese, d) for drugs
Slika 2: SEM-posnetki z vrsti~nim elektronskim mikroskopom
(SEM), ki ka`e strukturo aluminija: a) za gospodinjstvo, b) za ~oko-
lado, c) za sir, d) za zdravila
The corrosion investigation has been studied in the
presence and absence of magnetic field (Table 3, Figure
5 and 6).
3.1 Corrosion morphology of aluminum packaging foil
In order to correlate the accelerated electrochemical
tests with the real corrosion phenomena of aluminum
packaging foil, long-term tests involving an immersion
in the 0.3 % of mass fractions of NaCl solution were
realized. Figure 5 shows the corroded surfaces of
various aluminum packaging foils intended for domestic
use, chocolate, cheese and drugs under an light micro-
scope after 30 d of the immersion in 0.3 % of mass
fractions of NaCl at room temperature. On various
aluminum packaging foils, a local destruction of the
passive film was observed, having a localized-corrosion
appearance. No apparent corrosion was observed on
domestic aluminum packaging foil (Figure 5a). The
surfaces of the aluminum packaging foils intended for
chocolate and drugs appear to be more corroded (Fig-
ures 5b and 5d). The corrosion of the packaging foil for
drugs is oriented according to the privileged direction
(Figure 5d). The corrosion on the aluminum packaging
foils seems to be more controlled by the precipitate and
intermetallic-particle densities (Figures 1, 2 and 5).
The electrochemical responses of these alloys are
related to the precipitates and intermetallic particles
distributed heterogeneously on the surface, to the impu-
rities in the aluminum packaging foils and to the chloride
ions in the solution (Figures 5 and 6).
Table 3: Corrosion potential and polarization resistance of the
aluminum packaging foil for cheese in the presence and absence of the
magnetic field for a sample area of 1 cm2 in a 0.3 % of mass fractions
of NaCl medium
Tabela 3: Korozijski potencial in polarizacijska upornost aluminijeve
embala`ne folije za sir ob prisotnosti in odsotnosti magnetnega polja
za vzorec s povr{ino 1 cm2 v 0,3 % raztopini NaCl
Sample
Corrosion
potential
(mV)
Polarization
resistance
(k)
Presence of a weak magnetic field
after 1 h of immersion –560 4
Presence of a weak magnetic field
after 30 d of immersion –220 20
Absence of the magnetic field
after 1 h of immersion –645 20
Absence of the magnetic field
after 30 d of immersion –135 33
Other authors observed the presence of the AlSiFe,
AlFe, AlFeMn, and AlSi phases in alloys with the com-
positions similar to the alloys presented in this study.17–19
Okeoma Kelechukwu et al.18 observed the AlFeMn and
MnFe particles in the AA8011 aluminum alloy
containing 0.1 % of Mn used as a packaging foil. They
noticed that the presence of the Fe and Si elements in the
material support the precipitation of the dispersoids and
decreases the solubility of Mn in a solid solution. They
also noticed that the precipitation of Mn and other inter-
N. ZAZI et al.: CORROSION BEHAVIOR AND THE WEAK-MAGNETIC-FIELD EFFECT OF ALUMINUM ...
168 Materiali in tehnologije / Materials and technology 50 (2016) 2, 165–173
Figure 6: Microstructures of other batches of aluminum packaging
after 8 d of immersion in a 3 % of mass fraction of NaCl solution: a)
in the absence of the magnetic field, b) in the presence of a weak
magnetic field
Slika 6: Mikrostrukturi drugih serij aluminijevih folij po 8 dneh
namakanja v 3 % raztopini NaCl: a) v odsotnosti magnetnega polja, b)
ob prisotnosti {ibkega magnetnega polja
Figure 4: X-ray spectrum of the aluminum packaging foil for drugs
Slika 4: Rentgenogram aluminijeve embala`ne folije za zdravila
Figure 5: Microstructures of various aluminum packaging foils for:
a) domestic use, b) chocolate, c) cheese and d) drugs, after 30 d of
immersion in a 0.3 % NaCl solution in the absence of the magnetic
field
Slika 5: Mikrostruktura razli~nih aluminijevih embala`nih folij za:
a) gospodinjstvo, b) ~okolado, c) sir in d) zdravila, po 30 dneh nama-
kanja v raztopini 0,3 % NaCl v odsotnosti magnetnega polja
metallic particles definitely causes changes in the mor-
phology and electrochemical stability of the material
system. Sanders Jr. et al.17 noticed that AA8xxx foils
containing manganese in the order of 0.5 % promote the
formation of (Fe, Mn)Al6 intermetallic particles with the
average diameter of 0.1 1.5 μm. Paes et al.20 observed the
formation of (Fe, Mn)Aln and (Fe, Mn, Si)Aln in the
AA8006 material. Mondolfo21 reported the presence of
the Al3Fe and AlFeSi phases in the AA1050 aluminum.
Allen et al.22 reported three phases in 1xxx-series alumi-
num foils such as FeAl3, -FeSiAl5 and (AlFeSi).
After immersing the aluminum material in a corro-
sive environment, nobler phases in the aluminum matrix
such as AlSiFe, AlFe, and AlSi23 promote the dissolution
of aluminum in the matrix and the elements less noble
than aluminum. However, AlxFeyMnz phases can promo-
te the dissolution of aluminum in the matrix if the iron
concentration in a phase is much higher than the man-
ganese concentration, while on the contrary AlxFeyMnz is
dissolved if the iron is nobler than the aluminum matrix
and manganese is less noble than the matrix.23–25 In such
cases the behavior of intermetallic particles depends
principally on the potential difference between the
intermetallic-particle phase and the matrix.25
During cold working, precipitates and intermetallic
particles are fractured and redistributed in bands along
the rolling direction.26 The particles that contain copper
and iron represent cathodic particles compaed to the
matrix, supporting the matrix dissolution and the ones
that contain magnesium or/and manganese represent
anodic particles compared to the matrix, which dissolve
preferentially.26 The presence of the cathodic particles
increases the susceptibility to a localized corrosion.10
Iron- and copper-rich phases are catalytic sites for catho-
dic reactions and the sites for pits nucleation.
Using scanning electron microscopy after 30 d of
immersion, localized attacks were observed on the
surfaces of several aluminum foils (Figures 7a to 7d),
together with the destruction of the oxide-protective film,
probably due to the pitting and dissolution of aluminum
due to the chloride adsorption to the surfaces, thus
facilitating an aluminum oxidation of the A13+ ions.27 We
observed the traces of aluminum oxide Al2O3 on the
packaging foil for domestic use after the immersion
(Table 4). All the aluminums made from the primary or
recycled aluminum contain iron. Ambat et al.9 showed
that the presence of a small concentration of iron in
aluminum alloys leads to a localized corrosion due to
pitting. Our results (Figure 7) are in good agreement
with Ambat et al.9 The presence of chloride ions has a
harmful effect on the passive-layer formation. It leads to
an instability of passivation causing a localized corro-
sion. The material structure, composition and defects,
and the oxide structure, composition and thickness have
very significant influences on the aluminum-packaging-
foil corrosion.
Table 4: EDS analysis of a foodstuff foil in a roll (aluminum for
domestic use)
Tabela 4: EDS-analiza navite folije za `ivila (aluminij za doma~o
uporabo)
Before
corrosion
Ele-
ment
Energy
(keV)
Concen-
tration in
mass
fractions
(w/%)
Concen-
tration in
amount
fractions
(x/%)
Error
(%)
Al 1.486 100.00 100.00 0.38
O – 0 0 –
After 3
months
of corro-
sion
Zone
1
Al 1.486 95.96 93.68 1.97
O 0.525 4.04 6.62 5.60
Zone
2
Al 1.486 93.79 89.96 1.93
O 0.525 6.21 10.4 5.30
The corrosion microstructures of the cheese alu-
minum packaging foil in the 3 % of mass fractions of
NaCl solution after 8 d of immersion with or without a
weak magnetic field are compared. The effect of a weak
magnetic field on the morphology corrosion was
observed. In the case of the absence of the magnetic
field, the corrosion is located only in certain areas on the
N. ZAZI et al.: CORROSION BEHAVIOR AND THE WEAK-MAGNETIC-FIELD EFFECT OF ALUMINUM ...
Materiali in tehnologije / Materials and technology 50 (2016) 2, 165–173 169
Figure 7: Morphologies of the corrosion of various aluminum packaging foils after 30 d of corrosion in a solution of 0.3 % of mass fractions of
NaCl in the absence of the magnetic field: a) for domestic use, b) for chocolate, c) for cheese, d) for drugs
Slika 7: Morfologija korozije razli~nih aluminijevih embala`nih folij po 30-dnevni koroziji v raztopini 0,3 % NaCl in ob odsotnosti magnetnega
polja: a) za gospodinjstvo, b) za ~okolado, c) za sir, d) za zdravila
corroded-material surface, but with the samples corroded
under a weak magnetic field, the corrosion affected a
more significant area (Figure 6). At room temperature,
iron is ferromagnetic; this characteristic can explain
some changes in the morphology and the corrosion
kinetics under a weak permanent magnetic field. Several
authors: Devos et al.28 and Nikoli}29 showed that an
imposed magnetic field equal to or more than 0.3 T in
the study of Devos et al.28, and equal to 39788 A/m in the
study of Nikoli}29 causes various effects, in particular, on
the morphologies and structures of deposed metals or
alloys. However, the magnetic field used was not
permanent and the intensity of the field was not weak.
The authors attribute these effects to the Lorentz force of
electrolytic processes; this force affects the migration of
ions and induces a convective flow of the electrolyte
close to the electrode surface. This idea can also explain
the obtained results and the difference between the
corrosions with and without a weak magnetic field
because the ion migration and the convective flow affect
the corrosion phenomena.
Aluminum-packaging-foil environment (food and
drugs) is rich in oxygen, acid and salt. Localized corro-
sion attacks occur due to galvanic coupling between the
nobler particles and the more active aluminum-alloy
matrix, and between the less noble particles and the other
nobler phases (the aluminum matrix and nobler parti-
cles). A cathodic reaction of the oxygen and hydrogen
reduction occurs on the cathodic precipitate surface:10,30
O2 + 2H2O + 4e
– ⎯ →⎯ 4OH–
2H+ + 2e ⎯ →⎯ H2
The main anodic process, which happens in parallel
with the cathodic reaction, is the dissolution of the
aluminum matrix:10
Al ⎯ →⎯ Al+3 + 3e–
In the concave environment, we observed the pitting
of some aluminum packaging foil; the dissolution of
intermetallic particles with a round shape can explain
this observation that was also well discussed by Seri30. If
the less noble intermetallic particles are dissolved, they
enter the corrosion solution. If this solution is food or a
drug, it becomes toxic.
The investigation of the surface composition of the
aluminum packaging foil before and after three months
of corrosion in the 0.3 % of mass fractions of NaCl
solution, using an EDS analysis, revealed that the surface
of the aluminum foil for domestic use (foodstuff packag-
ing in a roll) was not varnished because the concentra-
tion of aluminum was 100 % before the corrosion (Table
4). After three months of the packaging-foil corrosion,
an aluminum oxide film was developed because the
oxygen concentration was increased (Table 4). The EDS
analysis of the foils intended for drugs, cheese and
chocolate show that the foils were varnished, but the
varnish film did not completely cover the aluminum
surface because the analysis before the corrosion showed
the presence of aluminum on the surface (Tables 5 to 7).
Part of the varnish dissolved after three months of the
corrosion in the 0.3 % of mass fractions of NaCl solution
as the analysis also showed an increase in the aluminum
concentration on the surface (Tables 5 to 7). Thus, the
aluminum surface became partially naked. This situation
is almost the same as in the case of the aluminum for
domestic use (Table 4).
Table 5: EDS analysis of a foil for drugs
Tabela 5: EDS-analiza folije za zdravila
Aluminum
foil before
corrosion
Ele-
ment
Energy
(keV)
Concen-
tration in
mass
fractions
(w/%)
Concen-
tration in
amount
fractions
(x/%)
Error
(%)
Al 1.486 15.05 7.86 0.31
O 0.525 25.33 22.30 0.70
C 0.277 59.54 69.81 0.17
Cl 2.621 0.08 0.03 0.42
Aluminum
foil after 3
months of
corrosion
Al 1.486 31.60 17.64 0.68
O 0.525 10.81 10.18 3.11
C 0.277 57.58 72.19 1.25
Table 6: EDS analysis of a foil for cheese
Tabela 6: EDS-analiza folije za sir
Aluminum
foil before
corrosion
Ele-
ment
Energy
(keV)
Concentra-
tion in
mass
fractions
(w/%)
Concen-
tration in
amount
fractions
(x/%)
Error
(%)
Al 1.486 0.68 0.37 0.13
O 0.525 43.98 40.73 0.24
C 0.277 43.85 54.09 0.11
Cl 2.621 11.49 4.80 0.16
Aluminum
foil after 3
months of
corrosion
Al 1.486 52.61 17.64 3.61
O 0.525 13.38 10.18 3.94
C 0.277 34.01 72.19 1.10
Table 7: EDS analysis of a foil for chocolate
Tabela 7: EDS-analiza folije za ~okolado
Aluminum
foil before
corrosion
Ele-
ment
Energy
(keV)
Concentrati
on in mass
fractions
(w/%)
Concen-
tration in
amount
fractions
(x/%)
Error
(%)
Al 1.486 23.96 18.20 0.16
O 0.525 04.96 6.36 0.46
C 0.277 30.43 51.93 0.58
Cl 2.621 40.65 23.50 0.23
Aluminum
foil after 3
months of
corrosion
Al 1.486 81.44 69.53 1.62
O 0.525 1071 15.42 4.57
C 0.277 7.87 15.06 9.06
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170 Materiali in tehnologije / Materials and technology 50 (2016) 2, 165–173
3.2 Kinetics of the corrosion and the dissolution of the
aluminum packaging foil
The results considered (Figure 8) show differences
between the corrosion kinetics for different aluminum
packaging foils. For an open-circuit potential, the taken
measurements present a high degree of dispersion of
values. The initial open-circuit potential, the passivation
open-circuit potential and the passivation time are diffe-
rent for different aluminum packaging foils. The diffe-
rences are due to the chemical compositions of the ma-
trices and the presence of different kinds of precipitates
and intermetallic particles in the alloy matrices, and the
differences between the chemical compositions of
different foils and the thermomechanical-treatment histo-
ries of the samples.
A complete electrochemical study of the aluminum
packaging foil with and without a weak magnetic field
was carried out only for the aluminum packaging foil
intended for cheese, because cheese has to be preserved
in a refrigerator. The open-circuit potential at the immer-
sion time of the aluminum packaging foil for cheese is
–0.62 V in the absence of the magnetic field and –0.638
V in the presence of a weak magnetic field (Figure 9).
The presence of a weak magnetic field seems to influ-
ence the corrosion kinetics in the first moments of
N. ZAZI et al.: CORROSION BEHAVIOR AND THE WEAK-MAGNETIC-FIELD EFFECT OF ALUMINUM ...
Materiali in tehnologije / Materials and technology 50 (2016) 2, 165–173 171
Figure 10: Polarization curves of the aluminum packaging foil for
cheese in a 0.3 % of mass fractions of NaCl solution:  presence of a
weak magnetic field 1 h after the immersion,  absence of the mag-
netic field 1 h after the immersion,  absence of the magnetic field 30
d after the immersion, presence of a weak magnetic field 30 d after
the immersion
Slika 10: Polarizacijske krivulje aluminijeve embala`ne folije za sir v
raztopini 0,3 % NaCl:  prisotnost {ibkega magnetnega polja 1 h po
potopitvi,  odsotnost magnetnega polja 1 h po potopitvi,  odsotnost
magnetnega polja po 30-dnevnem namakanju,  prisotnost {ibkega
magnetnega polja po 30-dnevnem namakanju
Figure 8: Open-circuit potential in the absence of the magnetic field
for aluminum packaging foils for:  drugs, domestic use,  choco-
late,  cheese
Slika 8: Potencial odprtega kroga ob odsotnosti magnetnega polja pri
aluminijevi embala`ni foliji za:  zdravila, gospodinjstvo,  ~oko-
lado,  sir
Figure 11: Magnifying-glass effect of polarization curves of the
aluminum packaging foil for cheese in a 0.3 % of mass fractions of
NaCl solution:  presence of a weak magnetic field 1 h after immer-
sion,  absence of the magnetic field 1 h after immersion,  absence
of magnetic field 30 d after immersion, presence of weak magnetic
field 30 d after immersion
Slika 11: Pove~an izsek polarizacijske krivulje aluminijeve embala`ne
folije za sir v 0,3 % raztopini NaCl:  prisotnost {ibkega magnetnega
polja 1 h po namo~itvi,  odsotnost magnetnega polja 1 h po namo-
~itvi,  odsotnost magnetnega polja 30 dni po namo~itvi,  prisot-
nost {ibkega magnetnega polja 30 dni po namo~itvi
Figure 9: Corrosion-free potential of the aluminum packaging foil for
cheese in a 0.3 % of mass fractions of NaCl solution:  absence of the
magnetic field,  presence of a weak magnetic field
Slika 9: Korozijski prosti potencial aluminijeve embala`ne folije za
sir v raztopini 0,3 % NaCl:  odsotnost magnetnega polja,  prisot-
nost {ibkega magnetnega polja
immersion. The magnetic-field effect appears more
visible later. The open-circuit potentials of the aluminum
packaging foil for cheese with and without a magnetic
field converge towards the same potential value of –0.03
V at the stationary regime and after 122 h of immersion
(Figure 9).
Figure 10 represents polarization curves of the
aluminum packaging foil intended for cheese and Figure
11 represents the magnifying-glass effect of the polari-
zations curves in the absence and presence of a weak
magnetic field after 1 h and after 30 d of immersion. The
presence of a weak magnetic field seems to increase the
potential of corrosion at the beginning of corrosion and
decrease it after 30 d of immersion (Figures 10 and 11;
Table 3), but the passivation-current density seems to be
increased at the beginning of corrosion in the presence of
a magnetic field (Figures 9 and 10). We also observed
that the presence of a weak magnetic field decreases the
polarization resistance at the beginning and after 30 d of
corrosion (Table 3), and decreases the passivation po-
tential at the beginning (Figures 10 and 11). Thus, a
weak magnetic field modifies the corrosion kinetics and
aluminum-packaging-foil dissolution as soon as the
corrosion starts. This result is in good agreement with
the work of Devos et al.31, except that the minimum
magnetic field applied by Devos et al.31 was a few
hundreds of mT.
The corrosion kinetics of aluminum packaging foils
in the 0.3 % of mass fractions of NaCl solution (Figures
8 to 10) compared to the work of Seri30 who studied the
Al1.4%Fe aluminum alloy, is different. This dissimilarity
is due to the difference between the chemical
compositions of the alloys or to the disparity between the
surface residual stresses.7
4 CONCLUSION
Based on the study combining microscopy, X-ray
diffraction, electrochemistry tests of aluminum packag-
ing foil and the EDS results, the following conclusions
were made:
• Various aluminum packaging foils underwent a loca-
lized corrosion in a 0.3 % of mass fractions of NaCl
solution, showing that the morphologies and the
corrosion kinetics are different for different foils,
depending on the chemical composition of the sur-
face.
• The application of a weak magnetic field modifies
the morphology and the kinetics of corrosion,
decreasing the polarization resistance, the passivation
potential and the corrosion potential at the beginning
of corrosion. However, it increases the density of
passivation current 1 h after the immersion of the
cheese aluminum packaging foil, increases the
corrosion potential after 1 h of corrosion and de-
creases the corrosion potential after 30 d of corro-
sion.
• X-ray diffraction results show the presence of a
textured structure with a preferential orientation.
• The passivation of the aluminum packaging foil in-
tended for cheese takes place after 122 h of corrosion
in the absence and the presence of a weak magnetic
field.
• The food packed in aluminum packaging foil can be
contaminated by the aluminum metal.
• The EDS results show the presence of aluminum
oxide on the surface after three months of corrosion.
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