Frosting By far the most common type of shaft current damage.
Parts affected are bearings, seals, thrust collars, journals, and to a lesser extent, gears.
The appearances is that of a sand blasted surface, characterized by overlapping, molten, shiny pit marks. If the entire available surface is affected, the damage may not be noticeable to the naked eye due to its satin-like appearance. The bottoms of the craters are round and shiny, indicative of the melting that had occurred. As EDM occurs, material is removed. The initial appearance of these tracks is that of scratches in the babbitted surface resulting from foreign particles in the lubrication or seal oil.