Definition
A corrosion-protection process applied to magnesium alloy parts in which the part is immersed in a hot solution of sodium dichromate. The treatment converts the surface of the magnesium into a stable chromate film that resists corrosion and provides a good base for paint or primer.
Plain English
A chemical bath that coats magnesium parts with a protective layer so they don't corrode and so paint sticks to them properly.
Context Anchor
Seen in aircraft maintenance and corrosion-control discussions, especially for magnesium parts such as wheels, housings, or castings.
Derivation
Chrome' refers to the chromate compound (sodium dichromate) used in the bath. 'Pickling' is an old industrial term for soaking metal in a chemical solution to clean or treat its surface — the same word used for soaking food in vinegar brine. Together it describes soaking magnesium in a chromate solution to protect it.
Why Pilots Care
Proper removal of chrome allows thorough inspection of critical parts, preventing in-flight failures from undetected defects.
Grounding Statement
Chrome pickling is a chemical surface treatment: it cleans corrosion from magnesium and leaves a protective film behind.
Intuition Check
Do not read “chrome” as shiny chrome plating, and do not read “pickling” as food preservation. In this maintenance context, it means a chromium-based chemical treatment for metal corrosion control.
Example Sentence 1
After machining the magnesium gearbox housing, the shop sent it out for chrome pickling before priming and painting.
Example Sentence 2
After chrome pickling, the exposed metal surface showed signs of wear that needed addressing before reassembly.