| This article focuses on phosphating mechanism and phosphating technology at room temperature. A new type of phosphate solution is developed. The function of every component in the developed phosphating solution and the influence of technical parameters on the phosphating coating are discussed.Experimental results of the investigation on the addition of calcium ion in the zinc series phosphating solution were described. When calcium ion is introduced in the zinc series phosphating solution, the properties of the phosphating film can be greatly improved. Crystals of the phosphating film become finer and corrosion resistance of the phosphating film has been improved. Amount of sediment in the phosphating solution is reduced dramatically. The solution is suitable for both anti-corrosion phosphating and phosphating for pre-electrophoretic painting process of mild steel work pieces in a variety of industrial fields.Through the research on phosphating mechanism and the improvement on the traditional phosphating art, a new phosphating process is developed. The formulation of solution used in phosphatizing process at room temperature was optimized by orthogonal test. A phosphatizing formulation was obtained which had very good properties such as easy preparation, fast process speed, good corrosion resistance and excellent surface status.The effects of the phosphating solution on the corrosion resistance and thickness of phosphating film are investigated by changing the composition of the solution and process conditions. The main control factors for Zn-Ca phosphating are studied. The research results show that the main factors affecting the forming rate and quality of phosphating film are: Zn2+/Ca2+, PO43-/NO3-, Ca (NO3)2, Zn (H2PO4)2, phosphating temperature and phosphating time. In addition, Zn-Ca phosphating is also affected by Fe2+, Ni(NO3)2 and accelerator to some extent. The composition of Zn-Ca phosphating solution is determined in accordance with the effects on each specification in phosphating process.The Zn-Ca system phosphating solution is composed of H3PO4, ZnO, Ca(NO3)2, Na6Mo7O24 and so on. The best matching of the phosphating working solution was got by orthogonal test. The optimum formula of phosphating solution obtained is that 7g/L ZnO, 22mL/L H3PO4, 10g/L Ca(NO3)2, 0.5g/L Ni(NO3)2, 2g/L C6H8O7, 1.5g/L NaNO2, 2.0g/L NaClO3, 2.5g/L Na6Mo7O24.Result shows that the uniform bonderizing coating with high corrosion resistance can be deposited at ambient temperature during ten or fifteen minutes. The drop method test of CuSO4 solution reaches 90 seconds, and anti-corrosion test in 3% NaCl solution reaches 3 hours, which accord with the domestic standard. The result shows that several factors, such as temperature, acidity, phosphating time, and pre-treatment, affect the formation, the appearance, the weight and the corrosion resistance of the phosphating films. The producing technology of the phosphating films is optimized and the quality of the films is obviously improved.It was shown that this phosphating bath is stable, less sludge and higher film-formation rate. The phosphating coating formed in this bath has a good anticorrosion property. Experimental results show that it overcomes such problems as yellow-out, surface dusting and poor corrosion resistance of conventional phosphatization at ambient temperature.From chemical, electrochemical, and thermodynamics, we studied on the phosphating mechanism. We discussed the feasibility of the phosphating at room temperature with thermodynamic calculation methods. We find phosphating process is difficult to proceed spontaneously in the absence of oxidants. Phosphating reaction heat must be self-sufficient, so the phosphorizing can be spontaneous at room temperature. Therefore, the key is to promote the development of a high efficiency accelerator. A number of oxidizing substances, heavy metals compounds and organic compounds can be used as phosphating promoters. We selected NaNO2 and KClO3 as oxidation accelerator.
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