Comparative Study On Corrosion Behavior Of 2024 Aluminum Alloy In Real Ocean Environment And Indoor Accelerated Test

The dissertation was based on the study of ocean atmospheric corrosion of 2024 aluminum alloy,which is commonly used as fuselage structure materials.The corrosion behavior of2024 aluminum alloy in the Xisha islands,which contained outdoor environment and under-shed environment,and indoor accelerated test were studied comprehensively.The corrosion law and corrosion mechanism of 2024 aluminum alloy in three environments were investigated,using weighing,morphological observation,material phases analysis and electrochemical test.The main research results are as follows:In the outdoor environment,pitting corrosion occurred on the surface of 2024 aluminum alloy in the early stage.After exposure for three months,the corrosion current density increased from 0.456μA·cm^-2 to 8.338μA·cm^-2.After exposure for 6 months,the corrosion developed into uniform pitting.The corrosion products was mainly composed of Al₂O₃·3H₂O.The corrosion products covered the surface and formed a layer of loose corrosion products,which had a certain inhibition effect on the corrosion,so the corrosion current density decreased to 2.359μA·cm^-2.After exposure for 12 months,the corrosion product layer fell off and became thin,so the corrosion current density increased to2.849μA·cm^-2.The corrosion dynamics conformed to the function W=0.00346t^0.73891,indicating that the corrosion products had a certain protective effect on the matrix.In the under-shed environment,slight pitting corrosion occurred on 2024 aluminum alloy in the early stage.After exposure for one month,the corrosion current density increased from0.56μA·cm^-2 to 6.92μAcm^-2.Due to the gradual accumulation of corrosion medium on the surface,intergranular corrosion occurred after exposure for three months,and the corrosion current density increased to 10.98μA·cm^-2.After exposure for six months,the network gap caused by intergranular corrosion was filled with loose corrosion products,mainly composed of Al₂O₃·3H₂O.After exposure for 12 months,the surface cracked due to the volume expansion of corrosion products.The corrosion kinetics was in accordance with the function W=0.0000025t^1.43026,indicating that the corrosion products had no protective effect on the substrate.In the indoor accelerated test,pitting corrosion occurred on 2024 aluminum alloy surface.After 48 hours,the corrosion current density increased from 0.96μA·cm^-2 to 29.2μA·cm^-2.When the test time reached 168 hours,uniform pitting corrosion occurred on the surface.The main component of pitting corrosion product was Al₂O₃·3H₂O,which covered the surface and had a certain inhibition effect on the corrosion,so the corrosion current density decreased to 6 9μA·cm^-2.When the test time reached 240 h,the corrosion product layer on the surface appeared to crack.The corrosion current density increased to 10.12μA·cm^-2.The corrosion kinetics conformed to the function W=0.00267t^0.87565.The corrosion product had a certain protective effect on the substrate.The corrosion behavior of 2024 aluminum alloy in outdoor environment was consistent with that in indoor accelerated test,which showed that in both environments,the corrosion current density first increased,then decreased,and finally increased again,and the corrosion products had a certain protective effect on the substrate.Therefore,indoor accelerated test is more suitable to simulate the corrosion process of 2024 aluminum alloy in outdoor environment.