CORROSION OF LEAD-BASED ELECTRODE MATERIALS

Abstract

The corrosion resistance of some lead-based alloys, obtained by metallurgical processing of battery scrap in sulphuric acid solutions both in the absence and in the presence of external polarization, is investigated. The focus is on the anodic corrosion or destruction of lead and its alloys, i.e. the change in electrochemical properties under the influence of the anode potential. To increase the durability of lead, alloying additives are introduced into it to form a more durable protective layer that impedes the lead ionization and reduce the area of anodic sections due to the formation of a non-conducting sulphate layer. Especially effective are the additives that form solid solutions, chemical compounds and eutectic with lead. Depending on the concentration of the alloying element in the alloy, it is possible to change the granularity, the structural or phase state, which increase the degree of the corrosion resistance of the electrode material. In this connection, both pure lead anode and lead alloys with some elements of s-, p-groups are used.

Calcium (0,2%) was included in the lead alloy as s-elements. The corrosion behavior of the alloy, both in the absence and in the presence of external polarization, does not change depending on the temperature (from 20 to 60^OC) and the concentration of sulphuric acid (from 1,0 to 4,0 n). The corrosion rate is linear. Calcium addition helps improve the mechanical properties and increase the anode resistance of lead.

Among the p- elements, the heaviest elements that have lattice parameters close to lead, the interatomic distances, atomic radii are of great interesi and form solid solutions and intermediate phases with lead.

The corrosion rate of a lead anode with a content of 1,7% Sb in the above conditions of the solutions does not change, and it is linear.

With a content of 5,0% Sb in solutions of sulfuric acid (from 1,0 to 4,0 n) in the absence of external polarization and in the presence of current in solutions of sulphuric acid (from 1,0 to 2,0 n), the corrosion rate is linear. In a 4,0 n solution of sulphuric acid and temperature (from 20 to 60^OC), the corrosion rate increases sharply. Corrosion is intercrystalline.