-
河南工程学院《专业英语》考查课
专业论文
Corrosion resistance of aluminum and
aluminum alloys
2015
年
11
月
15
日
Corrosion
resistance of aluminum and
aluminum
alloys
Yanghan
Department of
College of Mechanical Engineering
Henan
Institute of Engineering
605564494@
Abstract
：
The
failure caused by the corrosion-wear of molten
aluminum and its alloys is one of the
main
problems
in
aluminumindustry.
In
this
work,
the
resistance
behavior
of
various
materials,
including Fe-
based alloys, ceramics and corresponding
highapparatus of corrosion-wear in molten
aluminum and its alloys, were reviewed.
The synergistic effect of corrosion and wear
wasdiscussed
based on corrosion and
wear mechanics. The effects of dynamic agitation
due torotating of friction
pairs,
physical
propertyof
liquid
metal
and
size
of
grain
etc.,
on
the
corrosion-wear
resistance
performance
were
investigated.
In
addition,
the
characteristicsof
corrosion-
wear
resistance
performance
of
materials
in
molten
aluminum
and
its
alloy
were
summarized.
According
to
our
recentprogress
referred
to
kinds
of
materials,
especially
a
TiAl
3
/Ti
3
AlC
2
< br>/Al
2
O
3
composite,
the
ceramics/metal composites with aco-
continuous structure will be of great advantage in
the field of
corrosion-wear environment
of molten aluminum and its alloys.
Key
Words
：
molten
aluminum; aluminum alloy; corrosion; wear;
synergistic effect
1 Introduction
Corrosion-wear
is
one
of
the
extreme
states
presentin
engineering
process.
Different
from
corrosion-wear
inaqueous
media
which
have
been
found
primarily
basedon
an
electro-chemical
process,
the
corrosion-wear
inmolten
metal
involves
not
only
the
corrosion
caused
bythe
high
temperature molten metal, but also
thesynergistic effect between corrosion and wear,
whichresults
in much greater material
losses than the simplesum of losses by either
process alone. It is in fact a
kindof
mechanical?physical?chemical process that
involvesdissolution, diffusion, reactions in solid
and liquid, wearand interactionamong
changes in microstructure surface morphology, and
composition
ofthe interface
between solid and liquid
during this
processdegrade the physical
and
mechanical properties of thestructure
materials sharply . Molten aluminum andits alloys
are one of
the most aggressive metal
melts dueto their high chemical activity with
nearly all metals andmetal
oxides
.
Therefore,
the
solid
contaminationand
system
failure
resulting
from
corrosion-wear
ofmolten
aluminum are unavoidable in the
aluminum
[1]
.
2
Aluminum and Aluminum alloys
Aluminumis
a
white
light
metal.
Have
ductility.
Products
are
often
made
of
rod,
sheet,
foil,
powder, ribbon and
filamentous. A layer of oxide film that prevents
metal corrosion in wet air. The
content
of
aluminum
in
the
earth's
crust
is
third
only
to
oxygen
and
silicon,
and
it
is
the
most
abundant metal element in the earth's
crust. The development of three major industries
of aviation,
construction, and
automobile requires that the characteristics of
materials have unique properties of
aluminum and its alloys, which is
greatly beneficial to the production and
application of this new
metal aluminum.
Application is very extensive.
2.1 The
Category
(1) Wrought aluminum alloy
High strength, large specific strength
and suitable for plastic forming of aluminum
alloy
[2]
.
Deformation of aluminum alloy is also
divided into:
①
industrial
pure aluminum
②
heat treated
aluminum alloy
③
heat treated
aluminum alloy
(2) Cast aluminum alloy
The aluminum alloy which is suitable
for filling the mold to obtain a certain shape and
size of
the casting blank.
Casting aluminum alloy:
①
Al Si Alloys
②
Al Cu alloy
③
Al Mg alloy
④
Aluminum zinc alloy
2.2 The Grade
See sheet 1
for details.
Grade of
Aluminum and Aluminum alloys
Group
Pure aluminum
Aluminum alloy
with copper as the main alloying
element
Aluminum alloy with
manganese as the main alloying
element
Aluminum alloy with silicon as the main
alloying
element
Aluminum
alloy with magnesium as the main alloying
element
Magnesium and
silicon as the main alloying elements
and Mg2Si phase as the strengthening
phase of the
aluminum alloy
Aluminium alloy with zinc as the main
alloying
element
Aluminum
alloy with other alloy elements as the main
alloying elements
Spare
alloy group
9XXX
8XXX
7XXX
6XXX
5XXX
4XXX
3XXX
Brand Series
1XXX
2XXX
3 Anodic oxidation
surface treatment
The surface treatment
of aluminum and its alloy is mainly based on the
anodic oxidation. The
anodic
oxide
film
is
hard,
and
its
corrosion
resistance,
heat
resistance,
insulation
and
adsorption
capacity are also
better. In spite of this, the anodic oxide film in
a corrosive environment, still may
lead
to corrosion, especially small hole corrosion and
other local corrosion, so that the use of the
life of aluminum device has greatly
reduced, even using a very short time to complete
failure. Most
of the aluminum anodic
oxidation using sulfuric acid solution, the
formation of a larger membrane
pores,
resulting
in
surface
roughness,
reducing
the
film's
corrosion
resistance.
In
measuring
the
membrane resistance method and
electrochemical method has the advantages of fast
and direct. In
previous
studies
is
rarely
reported,
this
work
mainly
used
electrochemical
method
of
adding
glycerol of anodic oxide film on
aluminum alloy corrosion
resistance
[3]
.
3.1 Experment
3.1.1
Preparation of anodic oxide film and
postprocessing
Processing
technology
of
aluminum
anodic
oxidation
process:
aluminum
removal
of
natural
oxide
film,
chemical
polishing,
chemical
polishing,
anodic
oxidation,
and
thermal
sealing.
Oil
removal condition: 30g/L
NaOH, 25g/L
Na
2
CO
3
and 70
℃
, 2min. Remove the
oxide film process:
250ml/L
HNO
3
,
room
temperature,
chemical
polishing
process
for
5min.:
800ml/L
H<
/p>
3
PO
4
,
inhalation of 30ml/L
HNO
3
and 75
℃
3min
[4].
The
conventional
sulfuric
acid
solution
as
oxidizing
liquid,
anodic
oxidation
process
is
as
follows:150ml/L
H
2
SO
4
,
4~5
to
20ml/L
additive
glycerol,
time
60min.8
to
12V
voltage,
cathode
lead, room
temperature, coloring in 50 ~
60
℃
,2.5% alizarin red
solution. Finally, in hot water.
3.1.2
Performance detection
The
CHI604
electrochemical
testing
system
to
test
the
electrochemical
behavior:
a
three
electrode
system,
the
reference
electrode
and
saturated
calomel
electrode
(SCE),
the
auxiliary
electrode
is
a
platinum
(PT)
electrode,
anodic
aluminum
oxide
as
the
electrode;
in
3.5%
NaCl
solution Determination of polarization
curve and in anodic oxide film at the open circuit
potential
measurement of AC impedance
study of anodic oxide film on corrosion
resistance, AC impedance
measurements
in
the
frequency
range
0.01
~
100.00KHZ
and
by
scanning
electron
microscopy
(SUPER35)
observed the surface morphology of anodic oxide
film. By measuring samples before
and
after the film micrometer size, the average value
of 3 measurements.
3.2 Result and
analysis
Effect of oxidation current
density on the corrosion resistance of oxide film.
No additive, different current density
of the oxide film in sheet 2.
of
current density on thickness and color of oxide
film
J/(A/dm
2
)
d/(
?
·
m)
color
0.3
9
Pink
1.7
20
Pink
3.3
35
Dark red
5.0
34
Dark red
10.0
34
Dark red
Polarization curves of the oxide films
are shown in figure 1.
Figure of oxidation current density on
polarization curve of oxidation film
From
Figure
1,the
corrosion
resistance
of
the
oxide
film
is
best
when
the
current
density
is
3.3A/dm
2
.This is
mainly due to the formation of the film thickness
and dense, with good corrosion
resistance;the
flow
density
is
too
small,
the
film
is
slow,
the
film
is
dense
but
thinner,
so
the
corrosion resistance is
poor; current density is too high (more than
3.3A/dm
2
), the thermal
effect of
the oxide film increases, and
the oxide film is dissolved, and the corrosion
resistance is decreased.
The results of
the AC impedance measurement of the oxide film
under different current densities are shown
in figure 2. According to the complex
plane method for impedance values of anodic
aluminum oxide. Can be seen
from
Figure
2:
capacitive
arc
impedance
curve
only
high
frequency
region.
Current
density
from
0.3,
1.7,3.3A/dm
2
in
turn increases, the diameter of a semicircular
curve D
r
respectively 2010,
6003,
4600
Ω·cm
2
.And
its
value
increases
gradually,
namely
the
AC
impedance
of
the
oxide
film
increased
gradually;
current
density
more
than
3.3A/dm
2
electrochemical
impedance
spectrum
curve
of
the
semicircle
diameter
D
r
respectively
for
4000 and 2600
Ω·cm
2
, and 3.3
A/dm
2
value the AC impedance
of the film is decreased compared with that of the
film. Therefore, when the current
density is 3.3A/dm
2
, the AC
impedance of the oxide film is the largest, and
the
corrosion resistance is the
best
[5]
.
Figure 2. Effect of oxidation current
density on the AC impedance of oxide film
4
Corrosion-wear resistance
performance ofother materials
4.1
Intermetallics
In
recent
years,
increasing
research
interest
has
beenseen
in
the
development
of
IMCs.
Intermetallicsconstitute
a
unique
class
of
materials
that
have
manyexciting
and
advantageous
properties in a wide variety
ofapplications. A number of IMCs are also
beingdeveloped for use in
structural
applications.
Someexamples
of
these
materials
include
Ni
3
Al,
NiAl,
Fe
3
Si,and
FeSi.
Different Fe?Si IMCs
were fabricated bymechanical alloying and
annealing treatment, and FeSihad
the
best
anticorrosion
ability
in
molten
Al,
SiC
wasthe
next
and
Fe
3
Si
was
the
worst.
However,
themanufacturing
process of IMCs is very complex andcost-intensive.
4.2 Ceramics
Ceramics
including graphite, aluminosilicaterefractories,
AlN,
Si
3
N
4
,
and
Al
2
O
3
are widely
used foraluminum melting
applications. Refractories for dealingwith molten
Al face severe
corrosion and
degradationissues due to the extremely reducing
nature of molten tory
corrosion results
in the recession of hot face(working surface) due
to chemical reaction and
moltenmetal
penetration. Therefore, the focus of
refractorydevelopment has shifted to minimize
aluminum attackand subsequent
molten metal penetration
usingnon-wetting additives such as
BaSO
4,
SrSO
4
andAlPO
4
. The corrosion
resistance of ceramics canalso be improved by
decreasing
the porosity andcontrolling
their grain size to close open cracks in themolten
Al. The knowledge
gained in this
project hasenabled the development of some new
materials thatexhibit excellent
corrosion and wear resistance.
Onematerial is a castable refractory based on
calciumaluminate
(bonite) (CaO·
< br>6Al
2
O
3
< br> ), the other material is analumina/silicon
carbide
composite
material(approximately 53% SiC, 35%
Al
2
O
3
, and 12% Al or12% Si,
mass fraction). It is also an
alumina
–
siliconcarbide composite
refractory containing a continuousmicroscopic
network of
interpenetrating
microscopicscaled ceramic and metallic phases .
However, itslow toughness makes
ceramics hard for the fabrication
ofcomplex components, where stress-bearing is
arequirement .
5 Summary
This article reviews recent progress in
corrosion-wear resistance performance of materials
in
molten Aland its alloys.
In
addition,
the
test
apparatus
of corrosion-
wear in
molten metal
is
also
reviewed.
The
considerablevolume
of
research
on
corrosion-wear
of
metals
bymolten
Al
and
its
alloys can be ascribed to the
historicalinterest in the aluminum industry (such
as casting,die-casting
and
hot-dip-aluminizing).
Corrosion-
wear
isa
tribological
process
where
the
total
material
removalresults in simultaneous
mechanical wear and chemical two material-removal
mechanisms
dependon
each
other
in
a
complicated
way,
and
the
totalmaterial
removal
rate
is
usually
not simply the sum ofthe corrosion rate and the
wear rate measured in separateexperiments.
Corrosion
is
speeded
up
by
wear,
and
wearis
speeded
up
by
corrosion.
The
synergism
where
bothcorrosion
and
wear
are
significantly
increased
by
theinteractions
between
them
can
significantly increase totalmaterial
losses in molten aluminum ore, the damage
to materials due to thecoexistence of
corrosion and wear has a significantimpact on
economics of
engineering systems
bothdirectly and indirectly in terms of material
loss andassociated equipment
downtime
for repair andreplacement of corroded and worn
components
[6]
.
In
the last decade, the corrosion-wear
resistanceperformance of a large diversity of
materials
has
beenresearched
in
molten
Al
and
its
alloys,
including
metals,such
as
Fe-based
alloys
and
Co-
based alloys,intermetallics, high entropy alloys,
ceramics andmetal/ceramic composites. Among
the
materials
used
inaluminum
industry,
some
refractory
metals
such
as
W,
Tiand
Nb,
and
ceramics/metal
composites,
especially
in
aco-continuous
structure,
have
excellent
corrosion-wearresistance properties.
However, the refractory metalssuch as W, Ti and
Co, are very
expensive,
which
limitsthe
application
in
modern
aluminum
industry.
Generally,a
reaction
layer
composed of intermetallic compounds
isformed at the interface of metal and molten Al,
whichplays
an important
role
in
the corrosion-wear solubility,
thickness,
density, hardness
and
adhesionto substrate
have a great effect on the corrosion-
wearresistance performance of materials.
Although the ferrousalloys like H13
steel, which are widely used in thealuminum
industry, can be
easily attacked by
molten Aland its alloys, to some extent, the
lifetime of them can beimproved by
alloying
elements
and
multi-phasestructure.
As
for
the
ceramics/metal
composites,
maybe,the
co-continuous
construction will make it possible.