The Corrosion Behavior of Aluminum Alloy 7A04 under Cyclic Wet-Dry Immersion Conditions

The corrosion behavior of aluminum alloy 7A04 under cyclic wet-dry immersion conditions was investigated in 0.6 mol/L sodium chloride solution and 0.6 mol/L sodium chloride+0.02 mol/L sodium sulfite solution by Scanning electron microscopy (SEM), energy dispersive X-ray detection (EDS), X-ray photoelectron spectroscopy (XPS), mass loss method, mechanical capability test and electrochemical impedance spectroscopy (EIS). The results showed that the mass loss increases with corrosion time prolonging, and according with the rule as C=At(n), strength and elongation percentage are declining. Surface observation revealed that corrosion product is agglomerated and accidented. The corrosion products are Al(OH)(3) and aluminum chloride in 0.6 mol/L sodium chloride solution, and Al(OH)(3), aluminum sulfate and chloride in 0.6 mol/L sodium chloride and 0.02 mol/L sodium sulfite solution. The EIS results indicated that corrosion rate in 0.6 mol/L sodium chloride and 0.02 mol/L sodium sulfite solution is higher than that in 0.6 mol/L sodium chloride solution. The corrosion reaction mechanism was discussed.