磷化时间与温度对镁合金磷化膜的影响

目的研究钙系磷化液的磷化温度及时间对磷化膜结构与性能的影响。方法通过控制单因素变量,在不同磷化温度和时间条件下在镁合金表面制备磷化膜。通过扫描电镜(SEM)、X射线衍射仪(XRD)以及极化曲线测试等方法对AZ31镁合金表面磷化膜的形貌、结构与性能进行分析。结果镁合金表面钙系磷化膜呈花瓣状结晶生长,其主要成分为CaHPO_4·2H_2O。随着磷化时间的增加,磷化膜的厚度不断增加,但磷化时间过长使得磷化膜的平整度有所下降。极化曲线测试分析表明,磷化时间为30 min时,腐蚀电位与极化电阻最大,腐蚀电流密度最小,此时磷化膜耐蚀性最佳。当磷化温度为30℃时,磷化膜致密性最好,磷化膜的结晶度及覆盖能力在磷化温度为30℃时达到最佳。极化曲线测试结果显示,磷化温度为30℃时的磷化膜极化电阻最大,腐蚀电流密度最小,耐蚀性最优。结论磷化时间为30 min、温度为30℃时所得磷化膜的质量最好,耐蚀性最佳。

The Influence of Phosphating Temperature and Time on the Structure and Property of Phosphating Film on Magnesium Alloys

ABSTRACT:Objective To studythe influence of calcium phosphating temperature and time on the structure and property of phosphating film on magnesium alloys.Methods By controlling the single factor variables, the magnesium alloys were phos-phated under the condition of different phosphating temperature and time. The morphology, structure and properties of phos-phating film were analyzed by scanning electron microscope (SEM), X-ray diffraction (XRD) and polarization curve test respec-tively.ResultsSEM showed that the crystal shape of the phosphating film looked like petals, whose main composition was CaHPO4·2H2O. The phosphating film became thick with the phosphating time increasing, but its flatness became bad. The po-larization curve test showed when phosphating time was 30 minutes, the corrosion potential and polarization resistance of the phosphating film were maximum, the corrosion current density was minimum, and the corrosion resistance was the best. The result of SEM showed the density of phosphating film was the best at 30℃ phosphating temperature. The XRD result showed that the crystallinity and coverage of phosphating film were the best at 30℃. What’s more, its polarization resistance was maximum, the corrosion current density was minimum, the phosphating film had the best corrosion resistance.Conclusion The quality and corrosion resistance of phosphating films become the best at 30℃when the phosphating time is 30 min.