Zinc-calcium composite phosphating film was obtained by introducing PTFE(PTFE)particles into the zinc-calcium phosphating film through the process of phosphate precipitation and crystallization,and the effect of addition amount of PTFE particles dispersion solution and stirring speed on the microstructure,chemical composition,content of PTFE particles and thickness of the composite phosphating film and the corrosion protection performance of composite phosphating film on 16Mn steel were investigated.The results show that the different zinc-calcium composite phosphating films prepared by changing the addition amount of PTFE particles dispersion solution or stirring speed have uniform grain size,but they are scattered and disordered,and PTFE particles adhere to the grain surface and fill the pores between the grains,which can block the corrosive medium and hinder the corrosion electrochemical reaction,and obviously improve the corrosion resistance of zinc-calcium composite phosphating film.When the stirring speed is 300 r/min and adding amount of PTFE particles dispersion solution is 25 mL/L,many PTFE particles attached to the surface of the grains of the zinc-calcium composite phosphating film and the particles are evenly dispersed to fill the pores between the grains.The composite phosphating film contains Zn,Ca,P,O,C and F elements,the content of PTFE particles and thickness reach 4.1%and 12.4 μm,respectively,and has the highest charge transfer resistance 8528 Ω·cm2 and low-frequency impedance value 6015 Ω·cm2,showing excellent corrosion resistance.The corrosion protection performance of the zinc-calcium composite phosphating film prepared under the above condition on 16Mn steel is obviously better than that of con-ventional zinc-calcium phosphating film.
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