During corrugated board production, some manufacturers may observe that the grease used for corrugating rolls gradually turns dark or black. This phenomenon is not unusual and is typically caused by a combination of operating conditions and lubricant performance. Understanding the root causes helps improve lubrication management and extend corrugating roll service life.
High-Temperature Oxidation
Corrugating rolls operate under extremely high temperatures, typically above 180 °C, with peak temperatures reaching up to 230 °C in certain working conditions. Prolonged exposure to high heat accelerates oxidation of the lubricant. As the base oil and additives oxidize, long-chain molecules break down and carbonized residues are formed, causing the grease to darken or turn black.
Contamination from Dust and Debris
In production environments, dust, paper fibers, and fine metal particles may enter lubrication points. Once mixed with grease, these contaminants accelerate chemical degradation and oxidation, leading to faster aging and discoloration of the lubricant.
Moisture and Water Ingress
Moisture is unavoidable in corrugated board production due to steam and adhesive application. If the grease has insufficient water resistance, moisture intrusion can trigger emulsification or hydrolysis, damaging the lubricant structure and reducing its performance. This process often results in visible darkening of the grease.
Lubricant Quality and Additive Performance
Grease quality plays a critical role in color stability and performance. Lubricants with poor base oil quality or inadequate antioxidant and high-temperature additives are more prone to oxidation, coking, and discoloration under normal corrugating roll operating conditions. Low-grade greases may fail to provide long-term protection in high-load, high-temperature environments.
For high-temperature corrugating roll applications, selecting the right grease is essential. RMM-211 High Temperature Grease is designed to perform reliably under elevated temperatures, offering strong oxidation resistance and stable lubrication performance to help reduce grease darkening and extend bearing service life.
