不同时效态7050铝合金板材腐蚀速率测量

Effect of Aging Treatment on Corrosion Rate of 7050 Al-alloy Plate

采用失重、动电位极化和裂纹扩展速率测试方法,对不同时效态7050铝合金板材的腐蚀速率进行测定,并利用金相显微镜对浸蚀表面和纵截面的腐蚀形貌进行观察。结果表明:随着时效程度的增加,合金腐蚀类型由局部腐蚀逐渐向均匀腐蚀转变,腐蚀速率逐渐增加;而腐蚀裂纹扩展方式由沿晶腐蚀逐渐向穿晶腐蚀转变,导致腐蚀裂纹扩展速率不断减小;峰值时效态合金的腐蚀电流密度最大,欠时效态的次之,过时效态的最小。

Three groups of the same 7050 Al-alloy plates were all aged firstly at 121 ℃ for 6 h and then aged subsequently at 163 ℃ for 0,12 and 24 h respectively.The corrosion performance of the aging treated alloy plates was characterized by means of mass loss measurement,potentiodynamic polarization curve measurement and corrosion cracking propagation measurement,as well as optical microscope（OM）.The results show that the corrosion type of the aged alloy plates changed from localized corrosion to general corrosion gradually with increasing ageing time and the corrosion rate decreased constantly.Meanwhile,the manner of corrosion cracking propagation for the aged alloys transformed from intergranular to transgranular gradually with the increasing ageing time.This makes the rate of corrosion cracking propagation become lower continuously.The corrosion current density for the different aged alloy plates were assessed by potentiodynamic polarization technique,which may be ranked as the following order：peak-aged state 〉under-aged state 〉 over-aged state.