1、 Corrosion principle of aluminum alloy
The corrosion resistance of aluminum alloy depends on the stability of its surface oxide film in different environments. In a dry atmosphere, the passivation film on the surface of aluminum alloy is stable and not easily damaged. However, under long-term exposure to outdoor atmospheric environments, aluminum alloys may experience localized pitting corrosion. This is mainly because after the deposition of dust ions on the surface, an oxygen deficient zone is formed on the metal surface in the water film under the dust ions, resulting in the destruction of the passivation film and a decrease in self passivation ability.
2、 Corrosion of Aluminum Alloy in Outdoor Environment
Atmospheric environment: In industrial atmosphere, the protective film of aluminum alloy is easily damaged and its corrosion resistance decreases. Especially in areas polluted by sulfur oxide acid rain, the corrosion resistance of aluminum alloys decreases more significantly. The front of the aluminum material may generally turn black, with black spots densely distributed or gray white spots densely distributed.
Marine environment: In the marine atmosphere, chloride ions have a strong destructive effect on the passivation film of aluminum alloys. The passive state of aluminum alloy in seawater is unstable, and local corrosion is its main form of corrosion. Common localized corrosion includes pitting corrosion and crevice corrosion.
Other environments: Aluminum alloys may also be affected by electrochemical corrosion. For example, when in contact with dissimilar metal materials, the presence of alloy elements and impurities can cause multiple micro cells to form on the aluminum surface, leading to electrochemical corrosion.