【摘要】 时效时间对镁合金表面稀土转化膜的耐腐蚀性能有很大影响。将AZ63镁合金浸入硝酸镧和硝酸铈混合溶液中,在其表面制备稀土镧-铈转化膜并在空气中作0,24,48,60,72,90 h时效处理。利用循环伏安曲线、极化曲线、扫描电镜对AZ63镁合金稀土镧-铈转化膜在3%NaCl溶液中的孔蚀行为进行了研究。结果表明:时效处理能进一步提高稀土镧-铈转化膜的附着力、致密性和均匀性,从而显著提高镁合金的耐蚀性;稀土镧-铈转化膜的耐蚀性随时效时间的增加先增强后减弱,时效48 h时稀土镧-铈转化膜致密、附着力强,具有较好的耐蚀性,不易发生孔蚀,击穿电位为-1.418 V,孔蚀坑较浅;大电流密度更容易诱发孔蚀,当诱导孔蚀电流密度分别为0.4,1.5 mA/cm2时,时效48 h稀土镧-铈转化膜的诱发孔蚀时间为480,300 s。更多还原

【Abstract】 AZ63 Mg alloy was immersed into the mixed solution of lanthanum nitrate and cerium nitrate to generate dual rare earth( La and Ce) conversion film. As-obtained rare earth La-Ce conversion film was then aged for different duration. The pitting behavior of the aged rare earth conversion film in 3% NaCl solution was evaluated based on measurements of cyclic voltammetry curve and polarization curve as well as observation by scanning electron microscopy. Results indicated that aging treatment helped to improve the adhesion strength to substrate,compactness and uniformity of rare earth conversion film,thereby significantly improving the corrosion resistance of the Mg alloy. Particularly,the corrosion resistance of the conversion film increased initially and then decreased with the extended aging duration. The conversion film after 48 h of aging was compact and had high adhesion force as well as good corrosion resistance, showing a breakdown potential of- 1. 418 V as well as shallow pitted holes. Moreover,pitting corrosion of the rare earth conversion film was more easily induced at a high current density; and it needed 480 s and 300 s to induce pitting corrosion of the rare earth conversion film under an inductive current density of 0. 4 mA / cm2and 1. 5 mA / cm2.更多还原