When are solid lubricants used instead of liquid lubricants?

Solid lubricants are primarily utilized when conventional liquid lubricants fail to provide sufficient resistance to extreme loads or temperatures. While liquid lubricants like oils are highly effective for many applications, they may not be suitable in environments where their physical properties are compromised or where they cannot be maintained between sliding surfaces.12

Solid lubricants, which include materials such as graphite, molybdenum disulfide, and various polymeric films, are chosen for their high thermal stability and chemical inertness. They are particularly valuable in specialized machinery where they can function as sliding surfaces or protective films under conditions that would cause standard lubricants to deteriorate. Additionally, certain solid lubricants, such as polymeric films, are used in structural applications—like prestressed concrete construction—to facilitate movement caused by thermal expansion and contraction.13