Understanding Charge Effects on Marked Ball Wear Rates—a Corrosion Study: Part 1. The Impacts of pH and Chloride Concentration

The performance of grinding media can be misrepresented in marked ball wear tests due to galvanic interactions between dissimilar media. The possible galvanic interaction of media materials during marked ball wear tests has not been adequately explored. Corrosion rates and potentials of modern high carbon steel and high chromium white iron grinding media materials were measured using electrochemical testing as a function of pH and chloride content in a simulated mill water. The results replicate previous research with the high chromium white iron sample being more noble (higher corrosion potential) and corrosion resistant (small corrosion current) than high carbon steel. Using the experimental data and corrosion theory, the effects of galvanic coupling on corrosion rates were calculated to examine what could happen during a marked ball wear test or when a mixed media charge is present. This analysis indicates that high carbon steel can cathodically protect high chromium white iron leading to significant decreases in the corrosion rate (up to 99%) of this material during marked ball wear tests. The magnitude of the protection is a function of the pH of the mill water.

Automated summary

The performance of grinding media in marked ball wear tests can be affected by galvanic interactions between different media materials. However, the galvanic interaction of media materials has not been thoroughly studied. This research measured the corrosion rates and potentials of high carbon steel and high chromium white iron grinding media using electrochemical testing in simulated mill water. The results showed that high chromium white iron had higher corrosion resistance and potential compared to high carbon steel. The effects of galvanic coupling on corrosion rates were calculated, indicating that high carbon steel can cathodically protect high chromium white iron, resulting in significant decreases in corrosion rate during marked ball wear tests. The degree of protection depended on the pH of the mill water.