Definition
A chemical surface treatment for ferrous (iron-based) metal parts in which the part is dipped in a hot solution of phosphoric acid and manganese or zinc phosphate. The reaction produces a dull gray to black phosphate coating that bonds with the metal surface, providing corrosion resistance and a porous finish that holds lubricating oil well.
Plain English
A factory process that gives steel parts a rough gray-black coating to protect them from rust and help them hold oil.
Context Anchor
Seen in aircraft maintenance when discussing corrosion protection for steel parts, hardware, brackets, and some engine or landing gear components.
Derivation
Named after the Parker Rust-Proof Company, which developed and patented the process in the early 1900s. The trade name became the standard term for this type of phosphate coating.
Why Pilots Care
Recognizing a Parkerized finish helps in identifying genuine factory parts and understanding why some steel components look dull gray rather than polished or painted. The coating is functional, not cosmetic, and damage to it can lead to corrosion.
Intuition Check
Parkerizing is not paint. It is a chemical treatment of the steel surface that helps protect the metal and gives other protective coatings a better surface to hold onto.
Example Sentence 1
The steel landing gear bolts had a Parkerized finish to resist corrosion.
Example Sentence 2
Parkerizing the landing gear parts gave them a durable surface that held oil and resisted corrosion.