Solid Lubricants such as Molybdenium disulfide (MoS2), graphite, a number of metal sulfides, metal phosphates, metal powders and thermoplastic materials are being used in various forms to solve tribological problems in the boundary and mixed lubrication regime. In combination, these solid lubricants show synergistic effects with respect to friction and wear reduction.
Lubricant products formulated with these mixtures of solid lubricants come in form of powders, anti-friction coatings, pastes, greases and oils. A paste is a lubricant that consists of a mineral oil and/or synthetic oil base with or without thickener, active ingredients or additives as well as high solid lubricant content.
Solid lubricant containing pastes can be classified into 3 categories, for easy assembly, damage-free disassembly, optimum running-in, for operationally safe threaded connections and for maintenance-free continuous lubrication. Since the list of raw materials for use in food grade lubricants is limited, it was challenging to develop a food grade assembly paste. The result is a USDA H1 paste that is comparable in performance with fully formulated products.
Pastes are high performance lubricating products and are the most economic way to protect contacting metal surfaces. This is accomplished by creating a thin but solid lubricant layer that keeps the metal surface apart.
Pastes are usually composed of a carrier (such as mineral or synthetic oil) and more than 50% solid lubricants. This means users can easily, quickly and accurately apply the pastes with a brush or in some cases from an aerosol can. When the two metal surfaces come into contact, by sliding or rolling, a solid thin film is burnished onto the metal surface. This thin layer has extremely good surface adhesion and high film strength. Therefore the solid lubricant layers withstand extremely high pressures, avoid cold seizure, prevent wear and provide easy sliding at very low friction without stick-slip.
Properties
These properties provide the following benefits:
- Trouble-free machine assembly - without any surface damage
- No more run-in wear on drive gears for example. The solid lubricant film prevents abrasive wear and allows plastic deformation of tiny surface roughness.
- No more seizing - the high temperature stable solid lubricant layer of the pastes prevent metal contact of machine components and therefore welding.
As more lubricating needs were identified more pastes have been developed - each one providing a solution for various environmental conditions such as:
- Low temperatures
- Extremely high temperatures
- Corrosive environments
- Under water conditions
- Presence of splash water
Different pastes use different carrier oils. For example, some applications demand of compatibility with organic sealing materials or resistance against water. Others must work in corrosive environments and under extreme temperatures. For some of these environments only extremely pure oils are used. There are pastes for special operating conditions such as:
- Vibration or shock loads
- Clean environments (non staining)
- Presence of organic seals (compatibility)
- Sensitive alloys under stress (purity)
- Plastic components (compatibility)
Smart Lubrication Tips
Problem: You experience fretting and seizure on bolts in your plant exposed to low to medium temperatures and corrosive environments
Solution: The use of the metal-free lubricating paste Molykote P 40 can solve fretting and seizure problems in a corrosive plant environment
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This information has been sourced, reviewed and adapted from materials provided by Dow Corning.
For more information on this source, please visit Dow Corning.