Maintenance engineers who often have to choose between anti-seize lubricants and grease should be aware of the key differences between the two. As you’ll see, the choice between grease and anti-seize depends upon factors such as load, speed, and temperature.
Anti-seize products are used in shaft assemblies, nut-bolts, plugs, pipe fittings such as unions, high-temperature applications such as automobile exhaust assemblies, spark plug threads, brake components as well as screwed joints. Battery terminals are also a typical application.
How do they 'work'? Anti-seize products are formulated with micron-sized solid particles along with grease as the carrier. Primarily, the solid content enhances their load-carrying capacity as well as holding up under high temperature. It also reduces friction by ensuring lubrication under low-speed conditions.
Anti-seize products don't work well in equipment operated at higher speeds as there can be churning, heat generation, and the problem of jamming parts.
When operating under high temperatures (above 400 degree Fahrenheit), however, the anti-seize products help avoid seizure as well as galling, because they contain solid lubricants which have high-temperature resistance features and prevent metal to metal contact.
Anti-seize products contain solid lubricants such as graphite or metals having a somewhat lower coefficient of friction along with grease base, providing lubrication both at lower as well as higher temperature ranges. Solid content such as graphite, aluminum, and copper enhances the load-carrying capacity of the lubricant film even at lower temperatures. The high-temperature limit of the anti-seize depends upon the characteristics of the solid component used.
If the anti-seize product has to work in a very cold environment, the product containing nickel may be a better choice. Nickel-based products are also used in the oil and gas industry, where chemical resistance is a major requirement.
Graphite based anti-seize products are used in applications that require good electrical conductivity, as well as high temperature resistance (up to 900 degrees Fahrenheit), such as spark plugs threads and grounding connections. If the anti-seize is not used in these cases, metallic corrosion can result with increased electrical resistance of the threaded joint.
Advantages of anti-seize are:
- Very good high-temperature resistance
- Prevents rusting and galvanic corrosion
- Efficient assembly as well as disassembly of parts
- Good anti-seizing property
- Acts as sealant
- Conducts heat and electricity in some cases
- Inferior lubrication properties for high-speed applications
- Can attract contamination if on exposed threads
Grease is a natural choice for applications having light loads as well as high speeds. It is formulated with lubricating oil as well as a thickener. Most greases do not contain solids, whereas some contain a small amount of them. For temperatures exceeding 400 degrees Fahrenheit, grease may not be suitable, because it is nearly the flashpoint of the base oil. The base oil may oxidize and even burn at this temperature. The thin layer of lubricant now will not be able to carry its load at that temperature and metal to metal contact between surfaces in relative motion may happen. For large diameter (outer diameter) high-speed rolling contact bearings, the grease should be chosen according to the equipment manufacturer's recommendation. This applies to heavily loaded bearings as well.