Impedance Spectroscopy Study of Passive Layers
on the Surface of LeadTin and LeadTinCalcium Alloys
Anodically Oxidized in 4.8 M Sulfuric Acid Solution

M. M. Burashnikova^z, I. V. Zotova, and I. A. Kazarinov

Chernyshevsky State University, ul. Astrakhanskaya 83, Saratov, 410012 Russia

Received June 21, 2012

Abstract—The nature of passive films, which were formed at various potentials in 4.8 M H₂SO₄ solution on
the lead–tin and lead–tin–calcium alloys, is studied by the method of impedance spectroscopy. At the potentials
of 1.3 and 1.7 V, the electrode impedance is presented by the equivalent circuit, which corresponds to the for-
mation of a bilayer film consisting of lead(II) sulfate and oxide on the electrode surface. Lead(II) oxide, which
forms under the layer of lead sulfate, determines a high resistance of passive layer on the electrodes of lead
alloys under investigation. An introduction of tin into the lead alloys significantly decreases the resistance of
passive layers. An addition of calcium to the lead–tin alloy raises the impedance of the system. At a potential
of 2.05 V, a single-layer compact passive film forms on the electrodes of the test lead alloys. It consists predom-
inantly of lead oxides PbO_x (1 < x 2), which exhibit a higher electron conductivity. An introduction of tin into
the lead alloys decreases the resistance of formed films; calcium has almost no effect on the resistance of pas-
sive film under these conditions.

Keywords: lead–acid batteries, lead alloys, passive films, corrosion of lead alloys, impedance spectroscopy

DOI: 10.1134/S1023193513110037

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