Corrosion of lead-acid battery electrodes in sulphuric acid

Other Title(s)

تآكل ألواح نضيدة الرصاص الحامضية في حامض الكبريتيك

Dissertant

Hamad, Bakhtiar Kakil

Thesis advisor

Salih, Jalal Muhammad

University

University of Baghdad

Faculty

College of Science

Department

Chemistry Department

University Country

Iraq

Degree

Master

Degree Date

2004

English Abstract

The present work involved the investigation of the polarization behaviours of the following materials which consisted the electrodes and components of the lead acid battery which were: 1, lead alloy working electrode, 2, Grid lead electrode, 3, Pure lead electrode, 4, uncured positive electrode, 5, cured positive electrode, 6, uncured negative electrode, and, 7, cured negative electrode.

In 0.1, 0.25 and 0.56 M sulphuric acid solution in the temperature range (298-318)K in four different corrosion media which were: 1, un-stirred oxygenated sulphuric acid, 2, stirred oxygenated acid solution, 3, un-stirred deaerated acid solution, and, 4, stirred deaerated acid solution.

The major aspects of the work and the main results obtained may be presented as follows: 1- The polarization behaviour studies were performed on the different lead electrodes in the different media has been examined using a potentiostat and a scan rate of (30)mm per minute.

The potentioscan covered a range from –2.0 to +2.0 Volt.

The main results obtained were expressed in terms of the corrosion potentials (Ec) which became more negative in the un-stirred deaerated acid solution as compared with the oxygenated acid solution, and also in terms of corrosion current densities (ic) which became higher in the stirred oxygenated acid solution.

Thus, corrosion was more intense in the oxygenated acid solution as compared with the deaerated acid solution.

2- The corrosion potentials and the corrosion current densities changed considerably in the presence of the additives which involved :- 1, H3PO4 ( 11g dm-3), 2, A mixture of ( H3PO4(11g dm-3)+ FeSO4(0.2 g dm-3)), 3, NaCl (4 g dm-3) and , 4, FeSO4 (0.2 g dm-3).

In the stirred and the un-stirred oxygenated 0.56M sulphuric acid solution in the temperature range (298-318)K using the following working electrodes: 1, lead alloy electrode, 2, grid lead electrode, 3, cured positive electrode, and , 4, cured negative electrode.

Values of the corrosion potential (Ec) became more negative in the presence of H3PO4 and less negative with NaCl additives, the values of the corrosion current densities for all the electrodes were higher with NaCl and lower with H3PO4 in the both media.

3- The protection efficiency (p%) was investigated for the additives in the stirred and the un-stirred oxygenated 0.56M sulphuric acid solution.

Maximum values of p% were attained with H3PO4 and the minimum with NaCl.

4- Values of the thermodynamic quantities (DG, DW and DH) were estimated for the corrosion of the electrodes.

DG values were more negative in the deaerated acid solution in the absence of additives.

In the presence of the H3PO4, DG values were more negative while in the presence of NaCl the values were less negative indicating a greater corrosion feasibility in the former and smaller in the latter cases.

DW values extended over a wider range.

Such variation of DW values generally depended on the type and extent of the variation of DG vales with temperature.

As a result of such variations, values of DH were also found to a quire appreciably negative values.

5- The kinetics of the corrosion followed Arrhenius type rate equation.

A linear relationship existed between the values of the activation energy (Ea) and logarithm of the pre-exponential factor (log A) in the four different media suggesting the operation of a compensation effect in the kinetics of corrosion.

This suggests that, the corrosion reaction proceed on surface sites, which were associated with different energies of activation (Ea).

The corrosion reaction is assumed to start on sites with lower Ea and log A values first, spreading thereafter to these sites on which Ea and log A were higher.

Main Subjects

Chemistry

Topics

• Inorganic acids
• Sulfur acids
• Lead alloys

No. of Pages

138

Table of Contents

• APA
• MLA
• AMA

Language

English

Data Type

Arab Theses

Record ID

BIM-599912