balls when other variables are held at center level. The followingobservations obtained from Figs. 5 and 6: Increase of pH and solid content improved the mass loss of steelballs. This is possibility attributed to the fact that increasing pHcaused to formation of the passive ferric oxide film. Ferrous oxide isan insulator that prevents electron transfer, hindering corrosionand the weight loss of metal (or ball). On the other hand,increasing feed solids percentage increased the pulp viscosity which affectedthe abrasion rate. At higher pulp viscosity, the motion of the ballsand the copper sulphide samples were reduced significantly. If thepulp viscosity was too high, the balls and the sulphide sampleswould be stuck on the mill shell, significantly reducing the abrasionrate and at lower feed solids percentage; more oxygen will bedissolved in the pulp. Dissolved oxygen in aqueous solution hadprofound influence on the corrosion of metal. It was also seen that pH and solid content had effects of linear and quadratic on wear rate, respectively