What do Anti-Wear (AW) & Extreme Pressure (EP) Additives Do?
Most high-performance greases in the market today will have some form of extreme pressure protection and anti-wear performance. Ensuring equipment integrity & long-term operation are key for any premium lubricant. Maintenance managers and equipment operators won’t waste their time with cheap lubricants if it means having to buy new mechanical components every year.
Afton Chemical provides a broad range of specialty AW & EP additives to ensure the formulator can engineer a grease with the right balance between structural stability, surface activity, performance and cost.
Anti-Wear & Extreme Pressure Solutions
There are several additive technologies to help enhance AW & EP protection for today’s premium grease formulations. It’s important to consider both load and temperature when choosing AW & EP agents, as well as factor in compatibility with other additives, thickener systems and base oils.
ZDDP (Zinc Dialkyldithiophosphate)
ZDDP is an acronym for Zinc Dialkyldithiophosphate, also sometimes referred to as ZDTP, ZDP, or just "zinc." ZDDP is one of the most popular anti-wear additives because it is an effective way for a grease formulator to reduce wear and oxidation in a wide range of grease formulations. ZDDP additives work by breaking down to form a protective layer on the metal surface, which typically happens when exposed to heat. There are many different types of ZDDP and the differences in alcohol type (primary/secondary/mixed) and alcohol chain length can have a drastic impact on performance.
The alcohol type will determine the ability and ease of decomposition. ZDDP made with a primary alcohol has a higher thermal stability, meaning that it will need to be exposed to a higher temperature before it can be "activated" as an antiwear agent and put down a protective tribolayer. Conversely, ZDDP made with a secondary alcohol requires a lower activation temperature.
The alcohol chain length also needs to be considered as longer chain lengths provide more thermal stability. This results in ZDDP having LESS activity as an antioxidant or ability to provide extreme pressure protection. Shorter chain alcohols lower the thermal stability of ZDDP achieving greater ability to act as an antioxidant or extreme pressure agent.
The presence of “ash” in lubricants refers to the metallic compounds remaining after the oils have calcinated. Many high-performance anti-wear additives use metals to help provide protection from surface scuffing and fretting wear. However, these metals can create deposits that are harmful to the environment, especially in areas with exposure to high levels of humidity and extreme temperature. Ashless chemistries do not rely on these metallic components and offer an eco-friendly solution for grease formulators without sacrificing critical protective performance.
Sulfur Extreme Pressure Solutions
Additive technology that contains sulfur can help provide incredible extreme pressure stability through the formation of a sulfide layer at high temperatures. Sulfur containing additives can come in both active and inactive sulfur forms. Additives containing active sulfur react with the metal surface at lower temperatures than inactive compounds. It’s important to consider the final application for a grease when formulating, as sulfur compounds can have negative effects on certain metal types including yellow metals like bronze & brass.