14 C.F.R. § 25.609 Protection of structure.
Title 14 - Aeronautics and Space
Each part of the structure must— (a) Be suitably protected against deterioration or loss of strength in service due to any cause, including— (1) Weathering; (2) Corrosion; and (3) Abrasion; and (b) Have provisions for ventilation and drainage where necessary for protection.
Title 14: Aeronautics and Space
PART 25—AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES
Subpart D—Design and Construction
General
§ 25.609 Protection of structure.