Full definition
Bearing corrosion refers to the electrochemical or oxidative degradation of bearing surfaces, specifically the raceways and rolling elements. This degradation occurs due to various environmental factors, such as moisture, water, acids, alkalis, or electric current. The presence of these corrosive agents leads to the formation of pitting on the surface of the bearings, which acts as stress concentrators during operation. As these pits develop, they nucleate fatigue cracks, significantly reducing the service life of the bearings—by as much as 80% in severe cases. Two primary types of bearing corrosion are identified: moisture corrosion, which results from oxidation due to moisture exposure, and electric current corrosion, often referred to as fluting, which occurs when electric current passes through the bearing, leading to localized damage and wear.
To mitigate bearing corrosion, several protective measures can be implemented. Effective sealing solutions are crucial; they prevent the ingress of moisture and contaminants that can accelerate corrosion. Additionally, using grease that contains corrosion inhibitors can provide a protective film on the bearing surfaces, further enhancing their resistance to degradation. In more demanding applications, bearings made from stainless steel, such as AISI 440C, or those treated with Diamond-Like Carbon (DLC) coatings can offer superior protection against corrosion while maintaining optimal performance characteristics. These materials and treatments not only extend the service life of bearings but also help maintain their operational efficiency, which is critical in maintaining overall machinery reliability.
The ISO 15242 standard provides guidelines and testing methods for evaluating bearing corrosion resistance, thereby allowing manufacturers and users to select appropriate materials and protective measures based on specific operational environments. Understanding the mechanisms and impacts of bearing corrosion is essential for engineers and maintenance professionals to ensure the longevity and reliability of rotating machinery.