Corrosion Behavior Of Aluminum Alloy Welding Parts In Tropical Marine Atmospheric Environment

Tropical marine atmospheric environment is a severe corrosive environment with high temperature,high humidity,high salt fog and high light radiation,which causes serious corrosion to metal materials.6061 aluminium alloy has the advantages of high specific strength,light weight and good corrosion resistance.It is mainly used in marine atmospheric environment,and has been widely used in ship superstructure and marine equipment engineering in China.The manufacturing of materials and equipment can not be separated from welding,which will inevitably bring about changes in the structure and corrosion resistance of materials.Therefore,it is significant to study the corrosion behavior of aluminium alloys after welding by simulating tropical marine atmosphere in laboratory,which will guide the practical application of aluminium alloys.In this study,6061 aluminum alloy was welded by MIG welding and FSW welding with different process parameters.The welded joints with better mechanical properties and local corrosion resistance were selected to carry out periodic wetting corrosion test.At the same time,combined with ultraviolet irradiation test,the welding was studied by means of SEM,XRD,EDS and electrochemical performance test.The change and mechanism of corrosion behavior of materials before and after bonding in high temperature,high humidity and high salt spray environment,as well as the effect of ultraviolet light on Corrosion Behavior of materials.The results show that:MIG welding process parameters are welding current 110A,welding voltage 19V,welding speed 0.4m.min-1,showing better mechanical properties and higher local corrosion resistance;FSW welding process parameters are rotating speed 600r.min-1 and 1000r.min^-1,welding speed 150 cm.min^-1,showing mechanical properties and local corrosion resistance are similar,so this MIG welding process and two FSW welding process joints are selected as the test samples for follow-up simulation experiments.In the simulated tropical ocean atmosphere environment,the corrosion rates of Al alloy base metal and two friction stir welded joints were lower in the experimental period,which increased significantly in the medium term and slowed down in the later period,while the corrosion rates of MIG-2 joints were higher at the initial stage,gentle at the middle stage,and increased significantly at the later stage;the corrosion forms of base metal and its welded joints were all higher.Pitting corrosion and corrosion severity:MIG-2 process joints>FSW-2 process joints>FSW-1 process joints>base metal;corrosion products of base metal and its welded joints are similar,all of which are Al?OH?3,accompanied by a small amount of Al ₂?SO₄?₃,AlCl₃ and Al₂O₃,Al₂O₃ and Al?OH?₃ structure compactness,which has a certain protective effect on the matrix,and the looseness of Al₂?SO₄?₃ and AlCl₃structure accelerates the occurrence of corrosion.The atmospheric corrosion weightlessness of the pseudo-tropical ocean corrodes in accordance with the atmospheric corrosion law formula W=Atⁿ,and the kinetic equation fitted can predict the corrosion life to a certain extent.Ultraviolet light and dark contrast test results show that the corrosion weight loss of6061 aluminum alloy and its joint under dark conditions is lower than that under light conditions.In 30 days of experiment,the weight loss of base metal under ultraviolet irradiation reaches 300%under dark conditions,MIG-2 joint reaches 181%,FSW-1 joint reaches 155%,FSW-2 joint reaches 158%.The classification of corrosion products under ultraviolet and dark conditions is similar,mainly Al₂O₃.There are also a small amount of AlCl₃,Al?OH?₃ and AlO?OH?;ultraviolet irradiation can promote the corrosion of 6061aluminum alloy and its joints.