Nitrite, Nickel-Free Electrophoretic Coating Phosphating Solution
Cathodic electrophoretic coating is mainly used on automobile coating lines, before coating treatment the phosphating process is needed to enhance the adhesion and corrosion resistance of the coating layer. Currently toxic nitrite accelerator is widely adopted in the process of cathodic electrophoretic coating phosphating, as well as some polluting additives like nickel ions. Because of its great amount, phosphate solution become one of the major pollution sources on the automobile coating lines. In this study, the complex composed of non-toxic hydroxylamine, inorganic salts, etc. was chosen as phosphating accelerator, and without adding nickel ions, an environmental friendly cathodic electrophoresis phosphating solution was obtained. The phosphating film was compact, with good alkali resistance and good adhesion. Salt spray test showed that the cathodic electrodeposition coating had good corrosion resistance. As the hydroxylamine is stable in the phosphating solution, One-component phosphate concentrated solution can be produced.
Yafang Han, Fusheng Pan, Jianmao Tang, Chungen Zhou
X. C. Wang et al., "Nitrite, Nickel-Free Electrophoretic Coating Phosphating Solution", Materials Science Forum, Vol. 686, pp. 603-608, 2011