Solid lubricants – properties, types and which one to choose

WHAT ARE SOLID LUBRICANTS?

Solid lubricants are materials that create a separating protective layer between two surfaces and thereby prevent direct contact. Their basic function is to reduce the coefficient of friction and wear, supporting stable operation even under high loads or in unfavorable environments. The most commonly used materials include:

• graphite
• molybdenum disulfide (MoS₂)
• soft metals (aluminium, copper)
• PTFE (polytetrafluoroethylene)

 

Based on their mode of action, they are divided into three main groups.

Graphite (source: Addinol.de)

 

TYPES OF SOLID LUBRICANTS

Different solid lubricants work on the basis of different physical and chemical principles, which is crucial when selecting the right product for a specific application.

Structurally active solid lubricants are based on a lamellar crystal structure in which atoms are arranged in layers. These layers can carry high loads perpendicular to the direction of force while providing easy sliding in the tangential direction. As a result, materials such as graphite and MoS₂ provide extremely low friction even under high pressure.

Reactive solid lubricants work by chemically reacting with the material surface and forming a protective layer. This layer reduces wear and also protects against corrosion. Such lubricants are particularly effective in environments where mechanical and chemical stresses occur together, a process known as tribocorrosion.

Physically active solid lubricants include ductile materials with a low coefficient of friction, such as copper, aluminium, nickel and PTFE. Their action is based on mechanical adaptability and the ability to reduce friction without a chemical reaction.

 

FIELDS OF APPLICATION

The use of solid lubricants is particularly important in conditions involving boundary or mixed-friction conditions, meaning situations where the lubricating film is not fully established. Such conditions occur under high loads and low sliding speeds, as well as at extreme temperatures, where liquid lubricants lose their properties.

It is important to note that the use of solid lubricants in hydrodynamic lubrication conditions is not suitable, as it can negatively affect the performance of the lubricating film.

 

FORMS OF SOLID LUBRICANT USE

Solid lubricants in greases

In lubricating greases they are used as additives, with their content usually not exceeding 10%. Such greases are used in general industrial applications where additional wear protection is required.

Solid lubricants in pastes

Pastes contain a significantly higher proportion of solid lubricants, generally more than 40%, which makes them suitable for use under extreme conditions. Their advantage is resistance to very high temperatures, even above 1000 °C, as well as effective prevention of seizure and material welding.

Solid lubricants in bonded coatings

Spray coatings make it possible to apply a thin layer; after the solvent evaporates, a dry lubricating film remains. This lubrication method is used in applications that require a clean, precise solution without the use of liquids.

Illustration of friction between two surfaces (source: Addinol.de)

 

ADDINOL SOLID LUBRICANTS RANGE

For reliable operation and component protection, choose proven products of verified quality.

 

ADDINOL ANTI-SEIZE PASTE GAL

High-temperature assembly paste based on semi-synthetic oils with a lithium thickener and metal particles. Designed to protect threaded, mating and sliding contacts against seizure, wear and corrosion, and to make later disassembly easier.

 

Features and applications

• Prevents seizure of bolts, nuts and threaded joints
• Reduces friction and the stick-slip effect in sliding contacts
• Forms a protective separating layer under higher loads
• Protects metal surfaces against corrosion
• For assembly work in the steel industry, energy sector, chemical industry, machine rooms and mining

KUPI ADDINOL ANTI-SEIZE PASTE GAL

 

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ADDINOL MULTI-PURPOSE GREASE L 2 MO

Multi-purpose lithium grease based on mineral oil, with added MoS₂ and graphite. Used at mixed-friction contact points, under increased loads and slower movement, where additional protection of metal surfaces is required.

 

Features and applications

• Water-resistant and protects against corrosion and ageing
• MoS₂ and graphite strengthen protection of contact surfaces
• For plain and rolling bearings at low to medium speeds
• For lubrication points on machines, equipment and trucks
• Also usable in central lubrication systems

KUPI ADDINOL MULTI-PURPOSE GREASE L 2 MO

 

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ADDINOL LONGLIFE GREASE MG 1

Grease based on a lithium complex thickener and a viscous base oil. EP additives as well as MoS₂ and graphite strengthen the lubricating film during slow rotation of large bearings, higher loads and demanding operating conditions.

 

Features and applications

• EP additives for loaded bearing assemblies
• MoS₂ and graphite for additional protection of contact surfaces
• Protection against wear, corrosion and ageing
• For slowly rotating large bearings
• Use in rolling mills, rotary kilns, crushers and mills

KUPI ADDINOL LONGLIFE GREASE MG 1

 

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ADDINOL ADHESIVE LUBRICANT OG 0

A highly adhesive lubricating grease based on mineral oil with an aluminium complex thickener. Contains graphite for additional protection in loaded gear and sliding contacts and remains on the surface even under vibration and elevated temperatures.

 

Features and applications

• High adhesion to metal surfaces
• Graphite for protection of contact surfaces under load
• Reduces friction, wear and corrosion
• For large open gears, gear rings and gear racks
• Use in mills, kilns, crane systems and heavy construction machinery

KUPI ADDINOL ADHESIVE LUBRICANT OG 0

 

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