Definition
A chemical reaction in which a substance reacts with water and is broken down into simpler compounds. In aviation, hydrolysis is most often discussed as a form of degradation — for example, when moisture in fuel, hydraulic fluid, or composite materials reacts with the substance and breaks it down over time, weakening it or producing harmful byproducts.
Plain English
A process where water reacts with another substance and splits it apart into simpler pieces. In aircraft, this usually means moisture slowly damaging fluids or materials by chemically breaking them down.
Context Anchor
Seen in aircraft maintenance discussions involving moisture damage to fluids, coatings, plastics, rubber parts, or other materials.
Derivation
From the Greek 'hydro' meaning water, and 'lysis' meaning loosening or breaking apart. So hydrolysis literally means 'breaking apart by water' — which is exactly what the chemical reaction does.
Why Pilots Care
Explains long-term degradation of seals, adhesives, and composites that can affect structural integrity.
Grounding Statement
If water gets into a material and slowly changes what that material is made of, that process is hydrolysis.
Intuition Check
Hydrolysis is not just soaking, dampness, or rust. It means water is part of a chemical reaction that breaks a substance down.
Example Sentence 1
Long-term storage of hydraulic fluid in a humid hangar can cause hydrolysis, breaking down the fluid and reducing its effectiveness.
Example Sentence 2
Prolonged exposure to humidity can trigger hydrolysis in certain aircraft paints and sealants.