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

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 solution. The is consumed for the formation of a 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 or 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 1 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 to the 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 . When the Sn content in the alloy is below 1%, 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 crystals and facilitating their nucleation.