1) The SEM images of high carbon chromium steel balls were compared with low alloy steel balls. The results displayed that the corrosion of low alloy steelwas much more serious than that of high carbon chromium steel under the same conditions. The SEM/EDX analysis showed that the weight loss of balls is due to pitting corrosion and abrasion. The corrosion products formed from phases of Fe, O, S, Si and Cr. The low alloy steel balls that depend on a passive film for corrosion resistance were especially susceptible to pitting by local breakdown of the film at isolated sites. In addition, the SEM images indicated that there are fewer scratches and pits on low alloy steel ball surface.