Surface treatments serve to improve the running-in of piston rings and to inhibit corrosion within limits.
By chemical and thermal means, the surface of ring is coated with crystalline phosphates which absorbs oil and helps in lubrication and also wears away more easily than the base material of the ring, thus achieving a more rapid running-in.
- Chrome Plating:
Electro-deposited hard chromium plating on outer periphery has excellent wear and heat resistance. Generally speaking, a chromed ring lowers the wear by almost 50% but takes a longer time to run-in.
- Tin/Copper Coating:
Thin electrodeposited metallic coatings have a similar protective function as phosphating. They are somewhat softer than the material of cylinder and resist possible seizure by means of quasi-lubricating process.