The Effect of Selenium on the Electrochemical Behavior and Corrosion of Pb‐Sn Alloys Used in Lead‐Acid Batteries

Abstract

In valve regulated batteries of the adsorbed glass mat type the connecting strap and lugs of the plates (top lead) are covered by a thin liquid film of H2SO4 solution. The H2SO4 is consumed for the formation of a PbSO4 corrosion layer. The liquid film has high ohmic resistance and hence the strap and lugs of the plates are cathodically unprotected. As a result of this, often the life of the battery is limited by corrosion of the negative semiblock top lead. In battery manufacturing practice, Pb-Sn alloys are often used for the straps in the above battery type. The present paper examines creeping of the thin liquid film up a strap electrode, the structure and phase composition of the corrosion layer formed on the electrode surface, as well as the rate of corrosion of Pb-Sn and Pb-Sn-Se electrodes partly immersed in an absorbing glass mat soaked in H~SO~ or H~SO~ + Na2SO~ solutions. It has been established that the potential of that part of the electrode immersed in the solution controls the potential of the electrode up to a height of i cm above the solution level. The corrosion layer formed on the electrode surface above the solution (in the air) features zones of different phase compositions. The introduction of Na2SO4 to the H2SO~ solution leads to a sevenfold increase in corrosion rate of Pb-Sn alloys, while the addition of 0.03% Se to the alloy suppresses completely this effect of Na2SQ. When the Sn content in the alloy is below i%, the rate of corrosion increases. Selenium suppresses this effect, too, in alloys containing 0.6 % Sn. Selenium has an anticorrosion effect and acts as a grain refiner in Pb-Sn alloys decreasing also the size of PbSO4 crystals and facilitating their nucleation.

Selenium electrochemistry

“…33,35 Formation of H 2 Se often complicates the voltammograms. Chemical reaction of H 2 Se with Se(IV) can occur (eqn (13)). The reaction proceeds rapidly in acidic and intermediate pH ranges, but slowly in alkaline solutions.…”

“…10 The CIS/CIGS solar cell is a thriving energy sector. 11,12 Se acts as a grain refiner in the antimonial Pb used in grids and cell connectors of Pb-acid batteries 13 and has been investigated as a cathode material in Li-ion batteries. 14 The Se-based electrocatalyst has been investigated extensively as an oxygen reduction catalyst in fuel cell cathodes.…”

An Influence Study of Hydrogen Evolution Characteristics on the Negative Strap Corrosion of Lead Acid Battery

“…Hg/Hg 2 SO 4 ). Both potentials are higher than the surface potential of negative strap [4,6] . The oxidation reaction of Sb/Sn is slow, whereas the intergranular corrosion rate caused by Sb/Sn segregation is low.…”

“…Nevertheless, under the influences of solution ion diffusion, the oxygen-recombination and the hydrogen evolution reaction during alloy floating charge, the H + ionic concentration and SO 4 2-ionic concentration inside the liquid film are decreased with the increase of the distance away from the liquid level. According to certain researches [6] , the negative strap corrosion can be divided into three areas: (I) area under the cathodic protection, (II) lead sulfate corrosion area and (III) corrosion area in amorphous form, as shown in Figure 8. Figure 8, it can be seen that besides the change of electrode potential, the change of H + ionic concentration is also a key factor in affecting alloy corrosion during the process of changing from protected area (I) to area (II) with serious corrosion.…”

“…Researches about negative strap corrosion have been published in various documents [6][7][8] , and researchers hold different opinions about the cause of negative bus-bar corrosion. For example, Pavlov D et al [6] think oxygen absorption corrosion is brought by the lost cathodic protection of alloy resulting from the increased electric potential on negative strap surface caused by the oxygenation reaction depolarization. However, Hua S et al [7] regard the corrosion between negative strap alloys as a result of differences in negative strap alloy metallographic structures.…”