Piston rings are typically manufactured of cast iron, adhering to SAE J929 specifications. The cast iron is alloyed to provide the best combination of impact strength, temperature stability, and wear characteristics for most standard hydraulic applications. Alternative materials like nodular iron, bronze alloys, and stainless steel can also be used to solve complex or unique sealing applications.
As the standard protective coating per SAE AMS2481, manganese phosphate is applied to the surface of ferrous Z-LOK piston rings. Platings are also available that are designed to improve lubrication and enhance wear resistance.
Designing an application with three Z-LOK piston rings ensures long-term sealing performance. Foreign particles that are often present in a cylinder accumulate in outboard grooves and negatively impact the outer side face seal surfaces — but with the three-ring design, these particles remain trapped in the outboard grooves, allowing the center ring to function normally.