What is a Aluminum Oxidation?

Full definition

Aluminum oxidation is the formation of aluminum oxide on the surface of aluminum — it's why aluminum doesn't rust through like steel does. The thin oxide layer actually protects the underlying metal from further corrosion. Visible oxidation appears as a dull, chalky surface.

On gutters, the baked-on color paint prevents visible oxidation for 20+ years. Once the paint fades or flakes, oxidation starts showing as chalky streaks — cosmetic only, not a structural concern, but a sign the gutter is near end of life.

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