With the domestic and international energy saving, environmental protection and sewage discharge requirements continue to improve, Zirconium the traditional coating ternary phosphating pretreatment materials containing P, Mn, Ni and other heavy metal pollutants are gradually prohibited by local regulations, Zirconium the new green phosphorus-free conversion Membrane technology gradually mature and rapid development, the process can not completely use P, Mn, Ni, nitrite and other harmful substances, there are mainly zirconium salt pretreatment process, silane pretreatment process. On the same substrate, non-phosphorus pretreatment of nano-film and ternary phosphate film has considerable corrosion resistance, the current domestic new planning coating plant will generally consider the non-phosphorus pretreatment process, the traditional phosphating production line Also gradually began to switch to non-phosphorus production line. In this paper, the application of zirconium salt process in non-phosphorus pretreatment and traditional phosphide switching to zirconium salt were analyzed.
Ternary phosphating film thickness of 2 ~ 3μm, Zirconium zirconium salt conversion film thickness of 20 ~ 50nm, scanning electron microscopy (SEM) observation, zirconia film is more dense than ordinary phosphating film (Figure 1, Figure 2) The Phosphine film membrane between the gap, the film began to dissolve after dissolution, and gradually spread to the surrounding; zirconia film dense, no gap between the membrane, easy to produce membrane lysis, which has excellent corrosion resistance.
(SPC), galvanized sheet (GA), aluminum plate and other substrate, but in the treatment of anti-corrosion performance slightly different. The cold-rolled plates, Zirconium galvanized sheets and aluminum plates were used as substrates. The samples were prepared by ternary phosphating pretreatment and zirconium salt pretreatment respectively. After electrophoresis, the plates and cold-rolled plates were subjected to 960h SST (neutral salt spray ) Test, galvanized sheet for 26 cycles of CCT (cyclic corrosion)
The results of the comparative test show that the galvanized sheet is comparable to the anticorrosive ability after the zirconium and the post-phosphate treatment, but there are differences in the treated aluminum plate and the cold-rolled plate. Aluminum plate after the anti-corrosion treatment after the corrosion resistance than the zirconium treatment is poor, the maximum corrosion width of more than 2mm, and zirconium treatment of aluminum almost no corrosion, mainly aluminum through ordinary phosphating treatment, Zirconium there can not be on the membrane or membrane precipitation Of the phenomenon, fail to achieve the effect of corrosion, so phosphating in the treatment of aluminum when the need to adjust the content of F in the treatment solution to increase the amount of F ions on the corrosion of the plate in order to achieve corrosion requirements. The corrosion resistance of the cold-rolled plate after zirconization treatment is weaker than that of the phosphating treatment. Zirconium The maximum corrosion width is 4mm, mainly the zirconium film is too thin and the anticorrosive ability is poor after electrophoresis.
The traditional lead-free electroplating paint supporting zirconium salt pretreatment inner plate electrophoresis almost no film, the use of four box method for swimming penetration test, test data as shown in Table 2, the results show that: traditional electrophoretic paint 1 # supporting zirconium salt pretreatment is not Can be film, mainly zirconium pretreatment film is thin, Zirconium relative to the phosphating pretreatment of the membrane impedance is low (about 1/20 of the phosphine film), Zirconium and electrophoresis of the swimming force and pre-treatment of membrane impedance R0 is proportional to the resistance of the electrophoretic paint R is inversely proportional to , so supporting the pre-treatment of zirconia need to improve the swimming ability of electrophoretic coating, improved after the high swimming electrophoretic paint 2 #, swimming force can reach 60% about.