EP Additives

NiMAC Ltd is able to offer recommendations on extremely effective additives for improving the lubrication and extreme pressure properties of both neat oil and water based formulations.

Extreme pressure additives (EP additives) are incorporated into lubricants in order to reduce friction in high load applications. They work by reacting with the metal surfaces under extreme friction conditions, producing a protective film that prevents welding and surface damage.

Metalworking fluids usually utilise a synergistic combination of several extreme pressure and lubricity additives to provide the necessary performance for a given operation and to enhance the ability of metalworking fluids to provide extended tool life and improved surface finishes.

How Extreme Pressure (EP) Additives Work

Lubricants operate between moving surfaces to reduce friction, improve efficiency and reduce wear. The classical lubricant component used to prevent wear is called a boundary lubricity additive. A boundary lubricity additive, such as an ester, has a polar molecule that is attracted to the metal surface to form a thin film physical barrier that is difficult to penetrate and allows the interacting surfaces to slide over one another. In slow moving, highly loaded applications the boundary lubricity is unable to separate the interacting surfaces. Extreme Pressure (EP) additives are required to prevent wear and protect the components when the lubricating oil can no longer provide the necessary film thickness under these conditions. EP additives can be categorised as either temperature activated or non temperature activated.

Temperature activated EP additives

The three most common temperature activated EP additives are chlorine, phosphorus and sulphur. They are activated by reacting with the metal surface when the temperature is elevated due to friction causes by high loads. The chemical reaction between the EP additive and the metal surface forms a new compound that acts as a barrier to reduce friction, wear and the possibility of welding. These EP additives are effective over different temperature ranges;

Chloroparaffins 180-450°C
Phosphorus compounds 200-700°C
Sulphur compounds 600-1000°C

Non temperature activated EP additives

The non temperature dependent over-based sulphonate EP additives operate by a different mechanism and although the film formation is similar to the temperature dependent additives it does not need the elevated temperatures to start the reaction. Over-based sulphonates contain a colloidal carbonate salt dispersed within the sulfonate and during the interaction with iron the colloidal carbonate forms a film that can act as a barrier between the metal surfaces.

EP additives are particularly effective when used in combination as synergies can be obtained between sulphurised additives, phosphorus-based components and over-based sulphonates.