What is Parkerising?

• A. It is a process of alloying iron with phosphorus to improve strength.
• B. It is the production of surface films on iron and steel that are appreciably more resistant than the natural oxide film.
• C. It is a method of painting steel in grey color.
• D. It is a process of removing oxide layers from iron.

Answer: (B)

Parkerising is a phosphate conversion coating on iron and steel that forms a protective surface film far more resistant to corrosion than the natural oxide layer. The metal is treated in a phosphate bath (often zinc or manganese phosphate), which chemically converts the surface into crystalline iron or zinc phosphate. This coating is porous, providing a good base for oil or paint to adhere to, and it significantly enhances corrosion resistance. It’s not alloying with phosphorus, not simply painting a grey finish, and it doesn’t remove oxide; it creates a durable protective film through chemical conversion.