Effect of Ozone and Ni²⁺ on Phosphating on Carbon Steel Surface

The corrosion resistance of phosphated film obtained in the phosphating solution with ozone and Ni2+ was investigated.The results indicated that the film obtained from the phosphating solution with 1.62 mg/L dissolved ozone,0.8 g/L Ni2+,pH 2.75,at 40 ℃ for 5 min was dull-grey and dense,the weight of the film reached 6.19 g/m2,and the time of dropping corrosion resistance of CuSO4 was more than 109 s;increasing Ni2+ concentration to 1.6 g/L,the film weight was little decreased,and the dropping time increased to 127 s.The SEM showed that the coating was composed of biggish slab-like crystal grains and covered compactly on the substrate while ozone was 1.62 mg/L.The XRD showed that the main composition of the coating was Zn3(PO4)2·4H2O and Zn2Fe(PO4)2·4H2O with ozone existing;when ozone was 1.62 mg/L,the intension of plate Fe(110) was minimal which indicated that the surface of the carbon steel had been covered by phosphate coating narrowly.The electrochemical testing showed the film had good corrosion resistance.