低温快速电化学辅助磷化膜的制备及其耐蚀性

目前国内外关于电化学辅助磷化的研究报道较少。采用硫酸铜点滴试验、塔菲尔极化曲线研究了电化学辅助制备磷化膜的耐蚀性,探究电化学辅助磷化的最佳配方及工艺条件。通过单因素试验优化磷化液组分,通过正交试验优化工艺条件。结果表明,电化学辅助可以显著降低磷化温度、缩短磷化时间、减少磷化渣,优选出的磷化液组成为:5.00 g/L ZnO,13.00 mL/L磷酸(85%),20.00 g/L Zn(NO_3)_2·6H_2O,1.00 g/L酒石酸钾钠,1.00 g/L NH_4HF_2,1.20 g/L NaClO_3,5.00 g/L磷酸二氢锌,0.08 g/L CuSO_4;最优工艺参数为电流密度1.2 A/dm~2,温度35℃,通电时间7 min。最优工艺下所得磷化膜耐硫酸铜点滴试验时间达860 s;磷化时间1 min时,所得磷化膜硫酸铜点滴试验耐蚀性为61 s(远优于化学磷化的19 s),磷化膜外观均匀、致密。

Preparation and Corrosion Resistance of Low-Temperature and Quick Phosphating Coatings by Electrochemical Assistance

The corrosion resistance of electrochemical-assisted phosphating film was studied by copper sulfate drip experiments and Tafel polarization curve,and the optimum electrochemical phosphating formula and process conditions were investigated.The phosphating composition was optimized by single factor experiment and the optimized technique was obtained by orthogonal experiment.Results showed that the electrochemical assistance significantly reduced the temperature of phosphating,shortened the time of phosphating and reduced the amount of phosphating slag.The optimum composition of phosphating solution was as follows:ZnO 5.00 g/L,H3PO4(85％)13.00 mL/L,Zn(NO3)2 · 6H2O 20.00 g/L,potassium sodium tartrate 1.00 g/L,NH4HF2 1.00 g/L,NaClO31.20 g/L,Zn(H2PO4)2 5.00 g/L,CuSO4 0.08 g/L with the current density of 1.2 A/dm2,the phosphating temperature of 35 ℃ and the phosphating time of 7 minutes.The corrosion resistance of the phosphating film in the copper sulfate drip experiment reached 860 s.When the phosphating time was 1 min,the corrosion resistance of the phosphating film in the copper sulfate drip experiment was 61 s,which was much better than that by chemical phospating process.Besides,the obtained phosphate coating was more compact and the crystals of the coating were finer and more uniform.