The document presents a study on the corrosion behavior of aluminum-zinc alloy reinforced with ceramic particles such as flyash and silicon carbide in various acidic and alkaline solutions. The findings indicate that the composite exhibits superior corrosion resistance compared to the aluminum alloys when immersed in 5% NaCl and 2.5% HCl solutions. The research highlights the influence of immersion time and composition on the corrosion kinetics of the materials.

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International Journal of Mechanical Engineering and Technology (IJMET)
Volume 10, Issue 01, January 2019, pp. 661–666, Article ID: IJMET_10_01_067
Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=10&IType=01
ISSN Print: 0976-6340 and ISSN Online: 0976-6359
© IAEME Publication Scopus Indexed
CORROSION STUDIES ON CERAMIC
PARTICULATES REINFORCED HYBRID METAL
MATRIX COMPOSITES
U.Ramakanth
Research scholar, Dept. of Mechanical Engineering, Andhra University, Visakhapatnam
Putti Srinivasa Rao
Professor, Dept. of Mechanical Engineering, Andhra University, Visakhapatnam
ABSTRACT
In the present investigation the corrosion measurements were carried out in 5% NaCl
aqueous solution, 2.5% HCl. solution for predetermined time intervals and varying
percentage concentrations of HCl solution at room temperature. Kinetics of corrosion
effect on samples of Al-Zn alloy, Al-Zn –5wt% flyash and silicon carbide particles and
Al-Zn –10wt% flyash and silicon carbide particles as reinforcement in composite are
studied.
Keywords: corrosion, Al-Zn alloy, NaCl
Cite this Article: U.Ramakanth and Putti Srinivasa Rao, Corrosion Studies on Ceramic
Particulates Reinforced Hybrid Metal Matrix Composites, International Journal of
Mechanical Engineering and Technology, 10(01), 2019, pp.661–666
http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=10&Type=01
1. INTRODUCTION
Corrosion; defined as the destruction or deterioration of a metal or alloys by chemical or
electrochemical reaction or metallurgical interaction between the environment and the material.
It is a slow, progressive or rapid deterioration of a metal's properties such as appearance, surface
aspect, or mechanical properties under the influence of the surrounding environment. The basic
cause of corrosion is the instability of metals in their refined forms. The metals tend to revert to
their natural states through the processes of corrosion. Corrosion of metals and alloys used in
industry in aqueous environment, including its environment, is an electrochemical reaction. In
general, corrosion products exist as a thin adherent film, which merely stains or tarnishes the
metal and may act as a retardant to further corrosive action. In other cases, the products of
corrosion are bulky and porous in character, offering no protection [1].
2. LITERATURE
In general, ‘oxidation ‘is the term frequently used to designate ‘corrosion’. It is
thermodynamically reactive, but has excellent corrosion resistance due to the natural formation
of a thin, stable oxide film. Following factors affect the stability of the aluminum oxide causing

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corrosion. Oxide is not stable in acidic (PH
< 4) or alkaline (PH
>9) environments. Aggressive
ions like chlorides, fluorides may attack the oxides locally. Incorporation of Ga, Tl, Zn, Sn, Pb
may de-stabilize the oxide [2]. Pitting is a localized corrosion in the presence of aggressive
chloride ions. Pits initiated at weak sites in the oxide by a chloride attack [2, 3].
Keller and Edwards [4] reported that, intermetallic particles dissolve faster than the
aluminium rich matrix during the anodizing process and induce heterogeneous coatings with a
low corrosion resistance. Liu.et.al [5] stated that the cathodic nature of the CuAl2 particles,
compared to the aluminium rich α-phase, rise the corrosion potential of the α-phase causing
driving force for pitting corrosion in the α- solid solution. Electron beam welds of Al 2219 alloy
exhibit superior corrosion properties compared to the base alloy due to dissolution of CuAl2
particles and even distribution of copper in the matrix [6]. Wang et. al [7] stated that, Cu in solid
solution has more corrosion resistance than, when it is present as CuAl2, provided that the alloy
is not aged to the point when it becomes susceptible to intergranular corrosion or stress corrosion.
In addition, the Microstructural and the macro structural morphologies have a strong influence
on the corrosion resistance [8-11]. Recently pure metals macro structural [12, 13] and binary
alloy castings Microstructural [14, 15] effect on corrosion resistance reported. Corrosion
resistance depends on the cooling rate imposed during solidification which affects the solute
redistribution, dendrite arm size, and on the electrochemical behaviour of solute and solvent. The
role of CuAl2 intermetallic particles is important in conventional coatings or anodizing films [16,
17]. There have been extensive investigation on the role of chloride ions in the breakdown of the
passive film, repassivation and initiation of localised corrosion of aluminium and high strength
aluminium based alloys. The effect of alloying content [18-21], electrolytic composition [22],
heat treatment [23] and mechanical stress [24] on pitting and repassivation of aluminium based
alloys in chloride media have been reported. Aylor et al. [25] reported that the effect of
reinforcement on pitting behaviour of aluminium base metal matrix composites and observed
that pitting corrosion attack on SiC/AA2024 alloy composites predominantly at the SiC/Al
interfaces. Pits on the composites were greater in number, smaller in size, and shallower in depth
than on the alloy. Feng et al. [26] investigated the pitting corrosion behaviour of SiCp/Al 2024
aluminium metal matrix composites. They reported intense corrosion of the composites by pit
nucleation and propagation at the SiC/Al interface. Interfacial reactions between molten
aluminium and SiC, generated intermetallic particles which formed micro-galvanic couples with
the matrix. Zuhair et al., [27] investigated the electrochemical corrosion behaviour of powder
metallurgy aluminium alloy 6061/Al2O3 metal matrix composite in 3.5% NaCl aqueous solution.
Two composite compositions 10 volume percentage and 30 volume percentage of sub-micron
alumina particulates as the reinforcement phase by powder metallurgy processing were studied.
Cyclic polarization tests carried to determine pitting potentials and repassivation potentials in de-
aerated 3.5% NaCl solution. Several studies have indicated that the corrosion resistance of
particle-reinforced composites depends on the composition of the base alloy, reinforcing
particles, and corrosive environment [28-47].
In the present investigation the corrosion measurements were carried out in 5% NaCl aqueous
solution, 2.5% HCl. solution for predetermined time intervals and varying percentage
concentrations of HCl solution at room temperature. Kinetics of corrosion effect on samples of
Al-Zn alloy, Al-Zn –5wt% flyash and silicon carbide particles and Al-Zn –10wt% flyash and
silicon carbide particles as reinforcement in composite are studied.
3. MEASUREMENT OF CORROSION RATE
Corrosion rate can best be expressed in terms of “mpy” (millimetre per year). The following
formula can be used to obtain mpy of any type of aluminium alloys and composite.
Corrosion rate (mpy) = 534 W/DAT

3. Corrosion Studies on Ceramic Particulates Reinforced Hybrid Metal Matrix Composites
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Where W represents weight loss in milligrams, D is density of the alloy/composite in
gm./cm3
, A is area of the specimen in cm2
and T is immersion time in hours. The experimental
setup is shown in figure 1
Figure 1 Experimental setup for corrosion
4. RESULTS AND DISCUSSIONS
Two types of test solutions used, 5.0% NaCl aqueous solution and 2.5% HCl solution for
predetermined time intervals. Pitting corrosion occurs in aluminum, Al alloys and the composite,
both in acidic and basic aqueous solutions between PH
4 and 8.5. Within this range aluminum is
passive, because it is protected by its oxide film. The comparison curves are depicted in figure 2
Figure 2 Comparison curves

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4.1. Corrosion effect in 5% NaCl solution
Figure 2 shows the effect of immersion time on corrosion rate on Al alloys and the composite in
presence of 5% NaCl solution. Both alloys and composite show similar trend of dissolution i.e.
increase in dissolution with time. The following are the observations:
Composite shows superior corrosion resistance compared to both the alloys. Corrosion resistance
depends on the cooling rate imposed during solidification which in turn depends on the solute
distribution, dendrite arm size, and the electrochemical behavior of solute and solvent.
Figure 3 shows the corrosion effect on base alloy, pitting is observed at the grain boundaries.
With increasing dissolution, exposure of newer surfaces triggered the corrosion rate.
Figure 3 shows pitting corrosion on alloy immersed in 5% NaCl solution.
Figure 4 shows the corrosion effect on composite with lower contents of hybrid particles have
shown initially lower rate of corrosion.
Figure 4 Shows pitting corrosion on composite immersed in 5% NaCl solution.

5. Corrosion Studies on Ceramic Particulates Reinforced Hybrid Metal Matrix Composites
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5. CONCLUSIONS
1. Aluminium-Zinc alloy system A7075 reinforced with ceramic particles of flyash and
silicon carbide with 5 & 10 wt% were prepared. using vortex method.
2. Corrosion studies of both alloys and composite carried by immersion in dilute
solutions of acidic and alkaline media and method of corrosion studies evaluation is
by the loss in weight with time.
3. Both alloys and composite exhibit increased corrosion with increase in time of
immersion in electrolyte.
4. Composite shows more resistance to corrosion compared to both alloys in 5% aqueous
NaCl solution and 2.5% HCl solution.
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