The effects of water are insidious. Failure due to water contamination may be catastrophic, but it may not be immediate. Many failures blamed on lubricants are truly caused by acids which are able to form from moisture. The following are some of the effects of moisture present in oil:
Water attacks iron and steel surfaces to produce iron oxides. Water teams up with· acid in the oil and corrodes ferrous and nonferrous metals. Rust particles are abrasive. Abrasion exposes fresh metal which corrodes more easily in the presence of water and acid.
Water etching can be found on bearing surfaces and raceways. It is primarily caused by generation of hydrogen sulfide and sulfuric acid from water-induced lubricant degradation.
Erosion occurs when free water flashes onto hot metal surfaces and causes pitting.
The water droplet impacts a small area of the machine's surface with great force in the form of a needle-like microjet, which causes localized surface fatigue and erosion. Water contamination also increases the oil's ability to entrain air, thus increasing gaseous cavitation.
Hydrogen embrittlement occurs when water invades microscopic cracks in metal surfaces. Under extreme pressure, water decomposes into its components and releases hydrogen. This explosive force forces the cracks to become wider and deeper, leading to spalling.