Q345钢锰系复合磷化及硅酸钠溶液封闭处理

Manganese composite phosphating of Q345 steel and sealing treatment with sodium silicate solution

以Q345钢为试片进行锰系磷化、锰系复合磷化,在锰系复合磷化后用硅酸钠溶液封闭处理。对比不同磷化膜的微观形貌和耐腐蚀性能。结果表明:两者的晶粒都呈块状紧密堆积,锰系复合磷化膜晶粒间的孔隙基本被Al2O3颗粒填补,其孔隙率较低、致密度较高,且锰系复合磷化膜经封闭处理后致密度进一步提高。与锰系磷化膜相比,锰系复合磷化膜耐腐蚀性能较好,腐蚀电位正移约90 mV,腐蚀电流密度降至3.95×10^-5A/cm^2,电荷转移电阻增大近一倍,双电层电容减小近一倍。锰系复合磷化膜经封闭处理后,耐腐蚀性能进一步提高。Al2O3颗粒和硅酸钠都能填补晶粒间的孔隙,两者作用叠加使锰系复合磷化膜经封闭处理后具有较高致密度,从而表现出更好耐腐蚀性能。

Manganese phosphating and manganese composite phosphating of Q345 steel were carried out,respectively.Sodium silicate solution was used for sealing treatment after manganese phosphating.The microstructure and corrosion resistance of different phosphating films were compared.The results show that the grains of manganese phosphating film and manganese composite phosphating film both tightly agglomerate.The pores between the grains of manganese composite phosphating film are basically filled by Al2O3 particles.Manganese composite phosphating film has lower porosity and higher compactness,and the compactness of manganese composite phosphating film is further improved after sealing treatment.Compared with the manganese phosphating film,manganese composite phosphating film exhibits better corrosion resistance.The corrosion potential increases about 90 mV,the corrosion current density reduces to 3.95×10^-5 A/cm^2,the charge transfer resistance increases by nearly one time and the double layer capacitance reduces by nearly one time.The corrosion resistance of manganese composite phosphating film is further improved after sealing treatment.Al2O3 particles and sodium silicate can both fill the pores between the grains,and the superposition of two effects results in higher compactness of manganese composite phosphating film after sealing treatment,thus showing better corrosion resistance.