Performance of a valve regulated lead/acid battery is affected by the properties of the positive grid corrosion layer. An investigation has been carried out using a range of experimental techniques to study the influence of corrosion layer composition and structure on cyclic performance. A number of designs of battery were manufactured with different grids and positive active materials (PAMs). Two grid types were used consisting of either pure lead or a lead/tin alloy. Variations in PAM composition and structure were obtained by forming electrodes from grey oxide pastes containing additions of, red lead, tetrabasic lead sulphate, or sulphuric acid (sulphated). Results indicated that both grid alloy composition and PAM type affect the corrosion layer properties. Ultra-microtoming was used to prepare sections of the grid/corrosion layer interface. Results showed that corrosion propagated along tin rich grain boundaries.