纯镁和镁锂合金在中性3.5%NaCl溶液中的腐蚀行为

采用电化学方法研究了纯Mg和Mg-Li合金在中性3.5%NaCl溶液中的腐蚀行为,采用扫描电镜观察了腐蚀后的表面形貌,利用XRD测试了腐蚀前后纯Mg和Mg-Li合金表面的组成成分,并用失重法测试了腐蚀速率。结果表明:腐蚀初期,纯Mg的腐蚀电流小于Mg-Li合金,纯Mg的腐蚀电位高于Mg-Li合金,纯Mg的电化学反应电阻大于Mg-Li合金。经过24h腐蚀后,纯Mg的腐蚀速率大于Mg-Li合金,且两者腐蚀形貌不同,纯Mg的腐蚀坑大而深,蚀坑数量少;Mg-Li合金的腐蚀坑小而浅,蚀坑数量多并且表面变黑。纯Mg的腐蚀产物主要为Mg(OH)2,Mg-Li合金的腐蚀产物主要为Mg(OH)2,LiOH,MgLi,Mg3Li7,Al2O3。

Corrosion Behavior of Pure Mg and Mg-Li Alloy in 3.5%NaCl of pH=7

Corrosion behavior of pure Mg and Mg-Li Alloy in 3.5% NaCl solution of pH=7 was investigated through open circuit electrode potential vs time curve,polarization curve and impedance spectroscopy.The corrosion surface appearances were analysed by SEM,the surface components of pure Mg and Mg-Li alloy before and after corrosion were characterized by XRD,and the average corrosion velocity was detected by means of weight loss.The results indicated that pure Mg had less corrosion current,larger corrosion potential and electrochemistry reactive resistance than those of Mg-Li alloy in early stage of corrosion,but average corrosion velocity of pure Mg was larger than that of Mg-Li alloy after 24 h corrosion and the corrosion appearances were different.A few big and deep corrosion pits were formed on the surface of pure Mg,while the surface of Mg-Li alloy turned black and there were many little and shallow corrosion pits on it.The corrosion product on pure Mg surface was mainly Mg(OH)2,the corrosion products on Mg-Li alloy surface were consisted of Mg(OH)2,LiOH,MgLi,Mg3Li7,Al2O3.