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镁合金常规化学转化膜中含有Cr6+,对人体和环境有很大危害,且膜层较薄,耐蚀性有限,因此,采用水热法对其进行处理。通过场发射扫描电镜、X射线衍射和电化学测试方法,分别对水热法处理后的Mg-Nd-Zn-Zr镁合金表面膜层的形貌、相组成和耐蚀性能进行了研究。结果表明,形成的表面膜层主要由球形颗粒状和层片状的Mg(OH)2相组成,膜层厚度约可达20μm,且与基体结合牢固;经水热法处理后的镁合金在质量分数3.5%的NaCl水溶液中的开路电位比未处理的镁合金基体的正移了230mV,腐蚀电流密度降低了约1个数量级,且在阳极区出现了明显的钝化现象。
Conventional chemical conversion coatings on magnesium alloy contain Cr6 +, which has great harm to the human body and the environment. The film is thin and the corrosion resistance is limited. Therefore, it is treated by hydrothermal method. The morphology, phase composition and corrosion resistance of Mg-Nd-Zn-Zr magnesium alloy coatings treated by hydrothermal method were investigated by field emission scanning electron microscopy, X-ray diffraction and electrochemical measurements. The results show that the surface layer is composed mainly of spherical granular and lamellar Mg (OH) 2 phases with the thickness of about 20μm, and the bonding with the substrate is firm. The hydrothermally treated Mg alloy The open circuit potential in 3.5% NaCl aqueous solution was shifted by 230mV from the untreated magnesium alloy substrate, and the corrosion current density was reduced by about one order of magnitude. The obvious passivation occurred in the anode region.