Relation between pitting corrosion behavior and exposed area of high strength aluminum alloys in neutral salt spray

The pitting corrosion characteristics of high strength aluminum alloys(2A12 and 7B04) with different exposed areas(simulating the destructive section of coatings or film on the aluminum alloy surface) by neutral salt spray test were investigated. The corrosion area,pitting depth and pitting quantity were measured. The results show that pitting corrosion of 2A12 and 7B04 aluminum alloys are accelerated with the increase of exposed area in the neutral salt spray test. The maximum corrosion area of aluminum alloys increases with the exposed areas when it is less than 25 mm²; Moreover, the maximum pitting depth of 2A12 increases with exposed areas when it is less than 4 mm², while the maximum pitting depth of 7B04 increases with exposed areas when it is less than 100 mm². Component analysis of corrosion products indicates that the main components of corrosion products of 2A12 aluminum alloy are O, Al, Mg, Cu, while the corrosion products of 7B04 aluminum alloy are mainly O, Al, Mg, Zn. The different compositions of corrosion products causes their different structures, so that the pitting corrosion behavior of aluminum alloys is different.