稀土镧不同化合物对渗锌层耐蚀性能的影响

目的 研究稀土元素镧的不同化合物对渗锌层耐蚀性的影响.方法 在渗锌剂中不添加稀土元素及分别添加氧化镧、硫酸镧、氯化镧和硝酸镧,采用包埋法制备相关的渗锌层.通过使用TT260覆层测厚仪测量渗层厚度,利用SEM对渗锌层的表面形貌进行观察.配制质量分数为5%的NaCl溶液,进行全浸腐蚀试验,使用TG-328 A分析天平测量浸泡75 h和150 h的腐蚀失重,计算腐蚀失重速率,使用数码显微镜观察渗锌层腐蚀形貌.结果 与未添加稀土元素制备渗锌层的厚度33.0μm相比,在渗锌剂中添加稀土元素镧能够有效提高渗层厚度,添加氧化镧的渗层厚度上升至45.7μm,添加硫酸镧的渗层厚度上升至41.7μm,添加氯化镧的渗层厚度上升至36.1μm,添加硝酸镧的渗层厚度上升至43.1μm.观察不同渗锌剂制备渗锌层的表面形貌,添加氧化镧制备的渗锌层表面最均匀、致密,但渗层表面出现少许微裂纹.在盐水浸泡实验中,添加硝酸镧制备渗锌层的腐蚀失重速率在浸泡75 h和150 h时都是最小的,分别为0.0441 g/(m2·h)和0.0625 g/(m2·h),表现出十分优异的耐蚀性能.结论 在渗锌剂中添加稀土元素镧,能够提高渗锌的效率,改善渗锌层的表面质量,使得渗层更加均匀、致密,但渗层表面会出现少许不同程度的微裂纹.氧化镧、硫酸镧和硝酸镧的催渗作用十分明显,氯化镧的催渗效果最差.在耐盐水环境的腐蚀中,添加氯化镧制备的渗锌层的耐蚀性最不理想,而添加硝酸镧制备的渗锌层的耐蚀性最好.

Effect of Different Compounds of Rare Earth Lanthanum on Corrosion resistance of Zinc layer

Objective To investigate the effect of rare-earth element lanthanum on the corrosion resistance of zinc layer. Methods In this paper, lanthanum oxide, sulfuric acid lanthanum, as well as lanthanum chloride and lanthanum nitrate were added into zinc powder respectively, with an additive-free control, and the corresponding zinc layers were prepared by embedding method. The thickness and surface morphology of the zinc layers were studied by coating thickness gauge (model:TT260) and scanning electron microscope ( SEM) , respectively. Full immersion corrosion experiment was carried out in 5% ( mass fraction) NaCl solution, the 75 h and 150 h corrosion weight loss was measured by TG-328-A analytical balance measurement, and the corrosion morphology was observed by digital microscope. Results The effects of rare-earth element lanthanum on the thicknesses, surface morphology and corrosion resistance of zinc layers were compared. The results showed that the thickness of zinc layer was 33. 0 μm for the ad-ditive-free control, 45. 7 μm for lanthanum oxide, 41. 7 μm for sulfuric acid lanthanum, 36. 1 μm for lanthanum chloride, and 43. 1 μm for lanthanum nitrate. Zinc layer with lanthanum oxide had the optimal surface morphology, but a few micro cracks oc-curred on the surface. In salt water immersion test, the corrosion weight loss rates of zinc layer with lanthanum nitrate were the smallest both at 75 h and 150 h, which were 0. 0441 g/(m2·h) and 0. 0625 g/(m2·h), respectively, showing the excellent corrosion resistance. Conclusion Addition of rare-earth element lanthanum into zinc powder improved the efficiency of zinc impreg-nation, making the surface of zinc layer uniform and compact, but a few micro cracks appeared on the surface. The effects of lan-thanum oxide, acid lanthanum and lanthanum nitrate on the efficiency of zinc layer were obvious, but lanthanum chloride showed the least effect. In salt water environment, the effect of lanthanum chloride on the corrosion resistance of zinc layer was the least, while lanthanum nitrate had the best effect.