Simulating Study On Atmospheric Corrosion Of Aviation Aluminum Alloy

Based on in-suit corrosion monitoring in concealment area of civil airplane, LC4and 7075 aluminum alloys were studied in this paper. A new electrical resistancemethod was brought out, then the corrosion rates of aviation aluminum alloy inEXCO solution and under thin electrolyte layers were monitored by the model. Theelectrochemical characters of 7075 aluminum alloy such as electrochemical noise andelectrochemical impedance spectral in 3.5% chloride sodium solution and under thinelectrolyte layers were evaluated to conclude the corrosion process and mechanism. LC4CS aluminum alloy was determined by new electrical resistance method togo through pitting (<6h), intergranular corrosion (6～25h) and exfoliation (>25h) inEXCO solution. However pitting happened before 20h and exfoliation emerged after43h, when alloy immersed under thin electrolyte layers. In neutral 3.5% chloride sodium solution, corrosion rate of 7075T6 aluminumalloy was indicated to increase with thickness of thin electrolyte layers firstly and thendecreased, therefore it reached maximum when alloy was covered by 20 layers of lenstissue. Repairing of passive film of alloy under thin electrolyte layers was in dominantbefore 10h, which was characterized by much negative fluctuations of current noise.At 24h, breakdown of passive film exceeded repairing of that, which caused positivefluctuations of current noise and decreasing of polarization resistance. The passivefilm of alloy immersed in electrolyte was relative stable due to little probability ofpeaks in current fluctuations. 7075T6 aluminum alloy was polarized under thin electrolyte layers of neutral3.5% chloride sodium solution. The frequency of current fluctuations increased withthe polarization potential and thickness of thin electrolyte layers. The range of currentfluctuations increased with them and then decreased. At 1.0V, Pitting followed withemergence of current oscillation after 300s.