Antiwear Agent, also known as anti-wear agent in Chinese, is a type of key functional chemical added to lubricating oil. Its core mission is to prevent or reduce wear between metal surfaces under boundary lubrication conditions.

In simple terms, it is a protective shield for mechanical components in "dangerous moments".

1. Core question: Why are anti-wear agents needed?
In an ideal state, two moving metal surfaces would be completely separated by a complete oil film, which is known as hydrodynamic lubrication. However, in the real world, in many working conditions, this oil film is not sufficient to fully protect the metal:

When the equipment starts and stops

When under high load or impact load

At low speed and high torque

When high temperatures cause the viscosity of lubricating oil to decrease

In these cases, the oil film will thin out or even break, causing the protruding parts of the metal surface to come into direct contact. This kind of contact will cause a sharp increase in friction, a sudden rise in temperature, and lead to material wear, scratches, and even welding (i.e., "cylinder pulling" or "bearing seizing").

This lubrication state where direct contact may occur between metal surfaces is called boundary lubrication. Anti-wear agents were precisely developed to address the issue of boundary lubrication.

2. Main types and classic representatives
There are many types of anti-wear agents, but the most famous and widely used one is undoubtedly ZDDP (zinc dialkyl dithiophosphate). The T202, T203 and others we introduced earlier fall into this category.

In addition to ZDDP, common anti-wear agents also include

Phosphate esters/phosphites: For instance, T306, which contains no metals or sulfur and has low corrosiveness to copper alloys, is often used in hydraulic oils and gear oils that require compatibility with yellow metals.

Thiophosphates: Provide excellent extreme pressure and anti-wear performance.

Boron-containing compounds: As an environmentally friendly phosphorus-free, sulfur-free and metal-free anti-wear agent, they are one of the important directions for future development.

Molybdenum dialkyldithiocarbamate: This type of additive not only has anti-wear properties but is also an excellent friction modifier.

3. Mechanism of Action (" Sacrificial Protection"
The working principle of anti-wear agents is very ingenious. It is a typical mechanism of "sacrificing oneself to protect the metal" :

Physical adsorption and chemical adsorption: The anti-wear agent molecules contain polar groups, which will be attracted and adsorbed on the metal surface like magnets.

Chemical reaction: Under the trigger of high pressure and instantaneous high temperature (" flash temperature ") generated by boundary lubrication, the anti-wear agent molecules adsorbed on the metal surface will undergo a chemical reaction.

Form a protective film: The reaction generates a soft and easily sheared solid protective film. This film is usually composed of complex compounds such as phosphates, sulfides, and iron salts.

Preventing direct metal contact: When the protruding parts of the metal surface are about to come into contact, it is this pre-formed protective film that makes contact and is sheared. By sacrificing this thin film of its own, it avoids direct wear and biting between harder and more lethal base metals.

A simple metaphor: It's like applying a layer of soft soap between two pieces of glass that are about to rub. When friction occurs, what is worn away is the soap layer, while the glass itself is protected.

4. Main Functions and Benefits
Reduce wear: Significantly lower the wear of key components such as engines, gears, and hydraulic pumps, and extend the service life of equipment.

Prevent scratches and gluing: Under extreme loads, avoid welding and severe damage to the metal surface.

Reducing friction: Some anti-wear agents (such as molybdenum compounds) are also excellent friction modifiers, which can help improve energy efficiency.

Work in coordination with lubricating oil: It works in coordination with base oil and other additives (such as cleaners and dispersants) to form a complete lubrication protection system.

5. Application scenarios
Anti-wear agents are essential components of almost all lubricating oils and are widely used in:

Engine oil: Protects camshafts, tappets, piston rings and cylinder liners, etc.

Hydraulic oil: Prevents the hydraulic pump from wearing under high pressure.

Gear oil: Protects the tooth surfaces of gears, especially under heavy loads and impact loads.

Metalworking fluids: Protect tools and work during cutting and forming processes.

Compressor oil, etc.

The differences and connections with extreme pressure agents
Anti-wear agents are often mentioned together with extreme pressure agents. The two are closely related but have differences:

Anti-wear agent: It mainly acts on boundary lubrication conditions under medium load and temperature, preventing wear by forming a protective film. Its reaction film has a relatively low strength and is more prone to shearing.

Extreme pressure agent: It mainly acts under extreme conditions of extremely high loads and impact loads, generating a stronger chemical reaction film through chemical reactions to prevent scratches and adhesion. Its reaction is usually more intense.

In many oil products (such as gear oil), the two are used in combination to provide comprehensive protection from normal to extreme working conditions.