Study On Electrochemical Phosphating Technique Of Lead Alloy And Affect Factor

The chemical property of the lead is stable, in normal condition the lead is difficult to be corroded by environment medium. But in wet environment of damp and hot, it was easy to rust. In some field such as the aerospace industry which require the higher mechanical capability and resistance. The white rust, as a kind of corrosion product, will affect the use of lead alloy seriously. But with phosphating, the surface of the material will produce a film and this protection layer not only has no effect on the mechanical accuracy but also have the good mechanical capability and anticorrosion. A few of reports about the lead alloy phosphating researches in theory and technical exist. In consideration of the extensive application of lead in many filed, so the research of the phosphating technology and the affect factor of the lead phosphating is not only a defiant science problem, but also a practical engineering research.For avoiding the serious polarization in phosphating process, the potential of anisomerous square wave was put forward in this text according to the principle that the metals electrochemical phosphating and the lead was disposed in the phosphating solution of calcium-zinc series. Then the phosphating film was formed on surface of the lead which could resist corrosion. The Cyclic Voltammograms experiment was carry on in phosphating solution to choose the high potential and the low potential of the anisomerous square wave. Think that the shorter periods is propitious to making better film through the theories discussion.The electrochemistry experimentation include the linear potential scan, the AC impedance technology and the Tafel test was investigated in 3%NaCl solution to analyze the phosphating film. The results indicate that the phosphating film could prevent the corrosion of lead and the stability of the lead was improved after phosphating. The surface appearance of the phosphating film is observed by SEM and Atomic Absorption Spectrochemical analysis. The results show that the phosphating film was crystal type which appeared grainy structure and make up of zinc phosphate,calcium phosphate and lead phosphate. The zinc phosphate is the main.This text still studied the affect factor of the electrochemical phosphating process at the same time, proving that the temperature, the pH and the time phosphating is the important factor in phosphating process. Through the single factor experiment, the fitting formula as follows: the feasible temperature range is 60～75℃, pH is 2.2～2.6 and the time for phosphating 6～8 min.This phosphating process has advantage such as no harmful accelerant, free from pollution, environmental friendly and stable performance virtues. Thus it has application value in industry expansion.