When does micro-pitting occur?

Micro-pitting is a deterioration of metal as a result of fatigue. It can occur on gears. It can occur on steels the surfaces of which are harder than the cores. Very small pitting appears on the surface, making metallic surfaces appear grey in colour. The surface pitting worsens, becoming micro cracks. These defects can quickly lead to deeper flaking.
A specially formulated lubricant can prevent such defects from appearing.