Electrochemical study in sulphuric acid of the hardening L12 phases of Pb–Ca–Sn alloys

A study of the metallurgical transformations and of the electrochemical behaviour of Pb–0.08% Ca–x% Sn alloys has been performed. The corrosion resistance of five hardening L12 phases (Pb3Ca, Pb2SnCa, Pb1.5Sn1.5Ca, PbSn2Ca, Sn3Ca) has been characterised. It is found that high tin contents in alloys improve the mechanical properties and their corrosion resistance in sulphuric acid. Furthermore, the most favourable metallurgical state, i.e. the “aged” state appears stabilised by a tin content of around 2 wt.%. In the same manner, the rate of corrosion in overcharge conditions dramatically increases for Pb–Ca–Sn overaged alloys. These results seem to be linked to the tin level in the matrix, although the corrosion resistance of the L12 phases rises with the tin content.