Study On The Black Film Phosphating Of Steel

Phosphating treatment technology has been developed one hundred years . In modern times it has made a lot of new achievements. Excepically phosphating have been significantly broadened applications in the field of industrial ,this make it a important and indispensable technology in steel processing, preservation, decoration and other. The black film phosphating is an important surface treatment process as steel of anti-corrosion and decoration .The first this paper summarized the modern development process of the black film phosphating and acquired three kinds of possible experiments. This experiments were researched and studied and drawn the corresponding conclusions.Zn-Mn series black film phosphating at medium temperature is a more studied technology. It was added stabilizing agent in the experiment to improve the stability of solution and reduce the loss of the active ingredients phosphating solution. Rare-earth salt and copper sulfate compound used to make the color of phosphating film successfully changed from dark gray to black. The E-t curve of the film growth process was tested in the experiment. The results showed that the black agents maked the film's corrosion greatly enhanced.Two-step method is an important experiment method to study black film phosphating. Experiment 2 used the method of the first phosphating process and the second blackening. First, the basic zinc series phosphating solution was be used, and then the blackening solution. Blackening solution is an important factor to decide the color of film, while the acidity of blackening solution is a decisive factor. Through the effect of blackening was studied under different kinds of acid at different pH values, I found that the most satisfactory black film was be gained under the effect of the joint action of phosphoric acid and acetic acid. At the same time the phosphating and the blackening process were imposed the role of ultrasound can make the film adhesion greatly enhanced.Experiment 3 used the method of the first blackening and the second phosphating process. Through turning to papers and summarizing, a viable experimental method of direct blackening was reached, Cu - Mo - S system. The delicate black film was obtained under the conditions of pH value of 1.5 to 2. And then the Zn-Ni series phosphating solution was used .The phosphate film played a role of filling on the black film so that this enhanced the film's density and binding force and its corrosion resistance greatly.