Cu含量对一种新型Al-Mg-Si合金晶间腐蚀的影响

EFFECT OF Cu CONTENT ON INTERGRANULAR CORROSION OF A NEW TYPE Al-Mg-Si ALLOY

采用浸泡腐蚀实验和电化学实验研究了Cu含量变化和热处理条件对一种新型舰载飞机用Al-Mg -Si合金的耐腐蚀性能的影响 .结果表明 ,添加Cu后 ,实验合金的腐蚀方式由点蚀转变为晶间腐蚀 ,且腐蚀程度随Cu含量的增加而严重 ;与欠时效和过时效状态相比 ,T6态对晶间腐蚀较敏感 ,与晶界析出相的连续分布有关 .电化学实验表明 ,所有实验合金均较快进入钝态 ;随Cu含量的增加 ,实验合金的自腐蚀电位向正向变化 ,腐蚀电流密度增加 ;随时效时间的延长 ,点蚀电位、晶间腐蚀的临界点位和自腐蚀电位逐渐向负向变化 .而点蚀电位和自腐蚀电位随时效时间呈抛物线变化 。

The effect of Cu content and heat treatment condition on intergranular corrosion behavior of a new type Al-Mg-Si alloys,which is a candidate material for carrier-based aircraft,has been studied by immersion and electrochemical tests.The results of immersion test showed that the mode of corrosion changed from pitting corrosion to intergranular corrosion due to the addition of Cu into the alloy,the degree of corrosion became severe with increasing Cu content.Compared with the alloy under aged and over aged,the one treated according to T6 condition showed much strong susceptibility to intergranular corrosion,which was resulted from continuous distribution of precipitates along grain boundaries of the alloy at T6 status.The results of electrochemical test indicated that all the tested alloys may be passivated rapidly.The free corrosion potentials shifted to positive and the corrosion current densities of the alloys grew with increasing Cu content.The pitting potential,the critical potential for intergranular corrosion and the free corrosion potential shifted to negative with the increase of ageing time.The pitting potential and the free corrosion potential varied with aging time parabolically,however,the critical potential for intergranular corrosion linearly.