A Study On The Effect Of Zn～(2+),Mn～(2+),Ni～(2+) On The Phosphating Performance

Cathodic electrophoresis coating depends on its own excellent performance to beused widely in the automobile field. But there are electrochemical reactions in thecathodic electrophoresis coating, the phosphate film can be dissolved. So there is aproblem which phosphate film does not match with cathodic electrophoresis coating.If phosphate film does not match with cathodic electrophoresis coating better, thebody of the automobile does not have the excellent adhesion and corrosion resistanceperformance. The more cathodic electrophoresis coating is used widely, the more therequest of the phosphating is high.Zn²⁺,Mn²⁺,Ni²⁺ are important cations in the phosphating dissolution, and theyhave important effect on the phosphating performance. But the price of the zinc andnickel rise quickly. So the price of phosphating dissolution is higher recently. At thesametime, the disadvantage of Ni²⁺ is the problem which is not beneficial to healthand environment protection. There is an important economic benefit and social benefitto carry out the research of the effect of Zn²⁺,Mn²⁺,Ni²⁺ on the phosphatingperformance.The effect of Zn²⁺,Mn²⁺,Ni²⁺ on the phosphating are studied by adopting SEM,XRD,film weight. Which factors have effect on the "P" ratio of the phosphate filmand what the effect of "P" ratio of the phosphate film on the coating performance areinvestigated in the thesis.The results revealed that Zn²⁺ has important effect on film weight,crystallization, "P" ratio of the phosphate film. Mn²⁺,Ni²⁺ do not have obvious effecton "P" ratio. Mn²⁺,Ni²⁺ can make the crystallization thin obviously, make the filmmore uniform and compact, improved the film appearance; with the increasing ofMn²⁺,Ni²⁺ content, the film weight is decreased. During the cathodic electrophoresiscoating, "P" ratio of the phosphate film has an important effect on which phosphatefilm match with cathodic electrophoresis coating.The "P" ratio of the phosphate film has important effect on the film-paint filmdouble-layer performance. Studies have shown: the dissolution ratio decreased with the increasing of the "P" ratio of the phosphate film and the dissolution ratio increasedwith the decreasing of the "P" ratio of the phosphate film; the study on cathodicelectrophoresis coating adhesion and corrosion resistance indicate, the performance ofphosphate film-paint film double-layer with high "P" ratio is better than that of withlow "P" ratio in neutral salt spray test. When "P" ratio is above ninety percent, theadhesion and corrosion resistance of phosphate film-paint film double-layer is good.The difficulty of the thesis is that although the content of Mn²⁺,Ni²⁺ is only0.1g/L, the "P" ratio of the phosphate film is high. Studies have shown: the phosphatefilm with high "P" ratio can match with cathodic electrophoresis coating well, it isequal to the phosphate film performance with high content Mn²⁺,Ni²⁺.Although the content of Mn²⁺,Ni²⁺ is only 0.1g/L and the content of Zn²⁺ is1.2～1.6g/L, the phosphate film with high "P" ratio can match with cathodicelectrophoresis coating well. The phosphate film can do with the request of highperformance, low price, low pollution.