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用化学沉积的方法在镁合金AZ31表面获得了无铬、无氟和无亚硝酸盐的环保型化学转化膜。SEM,EDS及XRD分析表明,以磷酸盐和无氟添加剂为主要成分,在镁合金AZ31表面获得了致密、均匀和无网状裂纹的磷化膜。磷化膜厚度为12μm～15μm,主要物相为MnHPO_4·2.25H_2O,主要元素成分为O,Mg,P,Mn和Al。磷化后的镁合金AZ31通过中性盐雾测试(NSS),72h后未见腐蚀现象,浸涂氨基烘漆后的NSS测试达到204h未见明显腐蚀,结果表明磷化膜具有良好的耐蚀性能。电化学极化曲线测试结果显示,磷化后镁合金AZ31的E_(corr)比未处理的正移111mV,I_(corr)至少降低了三个数量级,磷化膜通过抑制阳极溶解和阴极析氢过程,有效地提高了镁合金AZ31的耐蚀性能。
The chemical deposition of non-chromium, fluorine-free and nitrite-free environment-friendly chemical conversion film was obtained on the AZ31 magnesium alloy surface. The results of SEM, EDS and XRD show that the phosphated film with compact, uniform and without network cracks was obtained on the AZ31 magnesium alloy with phosphate and fluorine-free additives as the main components. The thickness of phosphate coating is 12μm ~ 15μm, the main phase is MnHPO_4 · 2.25H_2O, and the main elements are O, Mg, P, Mn and Al. After phosphating AZ31 salt spray test (NSS), no corrosion after 72h, after immersion ammonia baking paint NSS test 204h no significant corrosion, the results show that the phosphate film has good corrosion resistance performance. Electrochemical polarization curve test results showed that the corr of AZ31 magnesium alloy after phosphating is at least three orders of magnitude lower than that of untreated positive 111mV and cor corr and the phosphating film inhibits the anodic dissolution and cathodic hydrogen evolution , Effectively improve the corrosion resistance of magnesium alloy AZ31.