周期凝露和二氧化硫环境对7A04铝合金腐蚀行为的影响

Effect of Cyclic Condensation and Sulfur Dioxide on Corrosion Behavior of 7A04 Aluminum Alloy

使用扫描电镜、交流阻抗谱和扫描开尔文探针等手段研究了7A04铝合金在周期凝露和二氧化硫条件下的腐蚀行为和规律。结果表明,7A04铝合金在周期凝露和二氧化硫环境中的腐蚀主要是薄液膜下的大气腐蚀,随着时间的延长腐蚀产物不断增多,腐蚀失重的数值增大,腐蚀产物的形貌呈点状或团状,主要是氢氧化铝和硫酸铝水合物;腐蚀类型主要为点蚀,局部有轻微剥蚀;交流阻抗拟合数值显示,在试验的初期7A04铝合金的腐蚀速率急剧下降,后期逐渐趋于平缓;表面电位分布图谱显示,材料表面的腐蚀电位呈升高趋势,至240 h后趋于稳定,7A04铝合金的腐蚀溶解,与其组织和组成分布密切相关。

The corrosion behavior of AI-alloy 7A04 under the condition of alternating condensation cycle with sulfur dioxide for 8 h and dry cycle for 16 h has been investigated by SEM, electrochemical im- pedance spectroscopy （EIS） and scanning kelvin probe （SKP）. The results show that the corrosion of 7A04 alloy in the sulfur dioxide containing environmental condition of condensation cycle seems to be is an atmospheric the corrosion under thin liquid layer, like atmosphere corrosion. The corrosion products in- crease with time. Mass loss value gradually adds. The results of surface observation show that corrosion product is in the shape or in clusters. Corrosion product is made up of alumina and aluminum sulfate hy- drate. The corrosion morphology shows mainly pitting corrosion and slight erosion. EIS simulation results exhibit that the corrosion rate of 7A04 alloy decreases sharply at the initial stage and gradually levels off at the later stage. Surface potential distribution maps reveal that the corrosion potential increase with cor- rosion time and become stable after 240 h, and the local active dissolution is related to the zonal distribu- tion of the Jntermetallic compounds.