The Study of Phosphate Film on Steel Surface with the Assistance of Cu[SC(NH₂)₂]₃²⁺ and Carboxyl Copolymer

Abstract

In our studied phosphating system we used the urea complex of copper (Cu[SC(NH2)2]32+) as the film promoter to instead of the nitrite and nitrate in traditional steel phosphating solution. We determined the changes of each component phosphate solution during specimen handling, and preliminary explorated the formation mechanism. Results showed that: compared to conventional zinc phosphating process the solution was stability, all the ferrous iron was formed the film, and FePO4 had not precipitated in the phosphating system; the phase of the phosphate film was formed by the small grain which was Fe2Zn(PO4)2•4H2O and Zn3(PO4)2•4H2O mixed in the proportional spherical crystals to instead of the Zn3(PO4)2•4H2O-based that was needle-like or leaf-shaped loose crystals.