Aluminum is an electronegative metal with an electrode potential of -0.5-3.0V, and the electric conductivity of 99.99% aluminum in 5.3% NaCL-0.3% H?O? for calomel reference is (-0.87+0.01) Although thermodynamically, aluminum is one of the most active industrial metals, aluminum is quite high in many oxidizing media, water, atmospheres, partially neutral solutions, and many weakly acidic and strong oxidizing media. stability. This is because in the above medium, aluminum can form a dense continuous oxide film on its surface, its molar volume is about 30% greater than that of aluminum, and this oxide film is under positive pressure when it is destroyed. It will be generated immediately.

       In general, the oxide film is stable in a solution of pH=4.0-9.0, and is also stable in concentrated nitric acid (pH=1) and concentrated sodium hydroxide (pH=13). The electrode potential of aluminum is largely determined by the insulating properties of the oxide film. Therefore, all factors that can improve the denseness of the oxide film, increase the thickness of the oxide film, and improve the insulation performance of the oxide film contribute to the improvement of the aluminum corrosion resistance. Conversely, any factor that reduces the effective protection of the oxide film, whether it is mechanical or chemical, will lead to a sharp decline in the corrosion resistance of aluminum.

       In general, the basic types of corrosion of aluminum and aluminum alloy profiles are: spot corrosion, galvanic corrosion, crevice corrosion, intergranular corrosion, stress corrosion, exfoliation corrosion, fatigue corrosion, filament corrosion, etc. Common corrosion phenomena in the production and use of aluminum building profiles.