Journal of Power Sources 162 (2006) 696–705
Effects of cell size and macrosegregation on the corrosion
behavior of a dilute Pb–Sb alloy
Daniel M. Rosa, Jos
e E. Spinelli, Wislei R. Os
orio, Amauri Garcia
Department of Materials Engineering, State University of Campinas–UNICAMP, P.O. Box 6122, 13083-970 Campinas, S˜ao Paulo, Brazil
Received 12 June 2006; received in revised form 6 July 2006; accepted 7 July 2006
Available online 14 August 2006
The aim of this study was to examine the effect of cooling rate on the cellular growth of a Pb–0.85 wt%Sb alloy and to evaluate the inﬂuences of
cell size and of the corresponding macrosegregation proﬁle on the resultant corrosion behavior. In order to obtain the as-cast samples a water-cooled
unidirectional solidiﬁcation system was used. Such experimental set-up has permitted the development of a clear cellular structural array even for
relative high cooling rates and has allowed a wide range of solidiﬁcation conditions to be analyzed. Macrostructural and microstructural aspects
along the casting were characterized by optical microscopy and scanning electron microscope (SEM) techniques. The electrochemical impedance
spectroscopy technique and potentiodynamic curves (Tafel extrapolation) were used to analyze the corrosion resistance of samples collected along
the casting length and immersed in a 0.5 M H
solution at 25
C. It was found that the corrosion rate decreases with increasing cell spacing
and that the pre-programming of microstructure cell size can be used as an alternative way to produce as-cast components of Pb–Sb alloys, such
as battery grids, with better corrosion resistance.
© 2006 Elsevier B.V. All rights reserved.
Keywords: Pb–Sb alloy; Battery grids; Cellular microstructure; Macrosegregation; Corrosion resistance
A battery grid must be dimensionally stable and have
mechanical properties which can resist the stresses of the
charge/discharge reactions without bending, stretching or warp-
ing. Additionally, the grid must not contain deleterious com-
ponents that would hinder recycling . The structural and
mechanical characteristics of lead–antimony alloys as well as
their precipitation hardening effect make them a very convenient
material for lead-acid battery positive grids [2–5]. Such alloys
are strong and creep-resistant and can be cast into rigid, dimen-
sionally stable grids which are capable of resisting the stresses
during operation [1,2]. It is also reported in the literature that
the antimony content of a Pb–Sb electrode affects the mechani-
cal properties, the microstructure, the electrochemical behavior
of active materials and corrosion layers on the electrode (up to
3 wt%Sb is used for SLI battery grids) [4,6].
Corresponding author. Tel.: +55 19 37883320; fax: +55 19 32894217.
E-mail address: firstname.lastname@example.org (A. Garcia).
Solidiﬁcation interface morphologies have been widely
investigated by many metallurgists, physicists and mathemati-
cians for several decades, in which cellular/dendritic growth
is one of the most complicated solidiﬁcation patterns and is
also the most prevalent form of crystallization. The cellular
and dendritic spacings are important microstructural parame-
ters resulting from the solidiﬁcation process, while it is well
known that these spacings exercise a signiﬁcant inﬂuence on
the properties of castings. They affect the microscopic segrega-
tion existing between the cellular or dendritic ramiﬁcations. The
growth of regular cells is favored by low growth rates and low
level of solute content during solidiﬁcation of alloys . Some
studies existing in literature have focused on the characterization
of cellular and dendritic growth of Pb–Sb dilute alloys [8–11].
In a recent article, Rosa et al.  correlated solidiﬁcation ther-
mal variables with the cellular growth of dilute Pb–Sb alloys for
transient unidirectional solidiﬁcation.
It has been reported in the literature that the macrostructural
and the microstructural as-cast morphologies affect the mechan-
ical properties  and have also a strong inﬂuence on the
corrosion resistance [14–17]. Recently, pure metals macrostruc-
tural  and binary aluminium alloy castings microstructural
0378-7753/$ – see front matter © 2006 Elsevier B.V. All rights reserved.