Antiwear additives are designed to protect metal surfaces under boundary and mixed lubrication conditions, where full fluid films cannot be maintained. Lubes’n’Greases consistently identifies antiwear additives as essential for preventing scuffing, adhesive wear and surface fatigue in engines and machinery.
The most historically significant antiwear additive is zinc dialkyldithiophosphate (ZDDP). Chemically, ZDDP reacts with metal surfaces under heat and pressure to form sacrificial phosphate-based tribofilms. These films prevent direct metal-to-metal contact and are consumed during operation, continuously renewing protection. Beyond wear control, ZDDP also provides secondary antioxidant benefits.
Antiwear additives gained prominence as engines became more compact and powerful, increasing contact stresses in valvetrains, gears, and bearings. Early lubricants lacked sufficient boundary protection, leading to rapid wear. ZDDP emerged as a highly effective solution and became a cornerstone of engine oil formulations throughout the 20th century.
ZDDPs are also used in hydraulics formulations, and although ZDDPs used in hydraulic oils are less thermally stable – there is no heat from combustion – there is still need controlled decomposition to protect surfaces.
Regionally, North America and Europe tightly regulate antiwear additive usage due to concerns about phosphorus impacting catalytic converters and emissions systems. This has driven reduced ZDDP treat rates and the exploration of alternative or supplemental antiwear chemistries. In Asia-Pacific, demand remains strong due to expanding vehicle production and continued reliance on internal combustion engines.
Market trends show a shift toward optimized antiwear systems rather than outright replacement of ZDDP. Lubes’n’Greases notes that formulators increasingly balance antiwear performance with emissions compliance, durability, and compatibility with other additives. Antiwear additives will remain critical as long as mechanical contact exists in engines, transmissions, and industrial equipment worldwide.