封闭处理对工程车用件磷化膜形貌和耐蚀性的影响

Effect of Sealing Treatment on Morphology and Corrosion Resistance of Phosphating Film on Engineering Vehicle Parts

使用以硅酸钠为主成分的封闭液对工程车用件表面的锌钙系磷化膜进行封闭处理。选取封闭液中硅酸钠的浓度、封闭时间和封闭液温度作为影响因素,并以电荷转移电阻和耐硫酸铜腐蚀时间作为评价指标,通过单因素实验考察了封闭处理工艺条件对封闭处理后的磷化膜耐蚀性的影响。结果表明:硅酸钠的浓度和封闭时间对封闭处理后的磷化膜耐蚀性都有较明显的影响,适当增加硅酸钠的浓度以及延长封闭时间有助于改善磷化膜的耐蚀性,而封闭液温度对封闭处理后的磷化膜耐蚀性的影响程度相对较小。当硅酸钠的浓度为12 g/L、封闭时间为16 min、封闭液温度约75℃,封闭处理后的磷化膜表面趋于平整,致密度较高,其耐蚀性较封闭处理前的磷化膜有明显改善。封闭处理可以进一步增强锌钙系磷化膜对基体的保护作用。

The zinc-calcium phosphating film on the surface of engineering vehicle parts was sealing treated with the sealing solution with sodium silicate as the main component.The concentration of sodium silicate in sealing solution,sealing time and temperature of sealing solution were selected as the influencing factors,and the charge transfer resistance and corrosion resistance time of copper sulfate were taken as the evaluation indexes.Through single factor experiment,the influence of sealing treatment process conditions on the corrosion resistance of the phosphating film after sealing treatment were investigated.The results showed that both the concentration of sodium silicate and sealing time have an obvious influence on the corrosion resistance of the phosphate film after sealing treatment.Appropriately increase of the concentration of sodium silicate and extension of sealing time were helpful to improve the corrosion resistance of phosphate film,while the temperature of sealing solution has a relatively small influence on the corrosion resistance of the phosphate film after sealing treatment.When the concentration of sodium silicate was 12 g/L,sealing time was 16 min and temperature of sealing solution was about 75℃,the phosphating film after sealing treatment has a flat surface and compact microstructure,its corrosion resistance was significantly improved compared with the phosphating film before sealing treatment.Sealing treatment can further improve the protective effect of zinc-calcium phosphating film to the substrate.