The Study And Application Of HAS Phosphate Process At Low Temperature

Phosphating technology is one of the most widely used surface treatment for steel nowadays. Developing low-temperature energy-conservation, nonpoisonous and low pollution phosphating craft has already become the main research direction now.As regards development of present phosphate process technologies, the zinc processes development trend is the use of low zinc or low zinc-manganese-modified processes. Comparing with the normal zinc phosphate layers, they display an outstanding corrosion-resistance performance.Under this background, this text changes the accelerator type and introduces the manganese ion and through orthogonal experiments optimizes the process. SEM, energy spectrum X-ray etc. physical detective means had been used to observe the microstructure and elements content. By means of the measurement of the time-potential change, polarization curve, the phosphating coatings performance has been studied. And investigated the effects of the acidity changes, the change of pH value, different HAS oxidant content on phosphating coatings, and forecasted the life-span of this kind of process. Electron microprobe has been used for analyzing the elements of phosphate coatings and observing the surface topography. In order to satisfy the painting request,this experiment reduces the weight of the phosphate coating by means of reducing the phosphate time and testing of the adhesion of the coatings has been carried out. It offered the basis for popularization and application of the phosphating technology and supplied references for the low-temperature phosphate research.The result shows : when pH value of the phosphating process is in the range of 3.05³.45, T.A. is about 31, F.A. is between 0.9 and 1.5, the coating formed is even, the color appears black gray; The coating weight is 5-12g/m²; The dropping test of CuSO₄ is more than 130s; 3% of the NaCl soaks for 3 hours there is no rusty spot appear; The microstructure is cosh-shaped by means of SEM; The life-span of this phosphate solution is calculated for 0.8m²/L tentatively; The sediment is 0.75g/L; Adhesion of the coating reaches standard level two; The optimized process is as follow:ZnO:(g/L) 7; accelerant C: (g/L) 5; HNO₃: (ml/L) 5; Na₂CO₃: (g/L) 4; H₃PO₄: (ml/L) 10; organic acid:(g/L)3; manganese salt: (g/L) 3; HAS:( g/L)3; Complexant A:(g/L) 3; accelerant B: (g/L) 0.05; Na₂MoO₄:(g/L)0.1;This process t has been optimized further through adjusting the pH of the solution and reduces the cost. This makes the process come nearer the practice.ZnO:(g/L) 5; accelerant C: (g/L) 3; HNO₃: (ml/L) 5; Na₂CO₃: (g/L) 4; H₃PO₄: (ml/L) 8; organic acid: (g/L) 0.5; manganese salt: (g/L) 6; HAS:( g/L)2; Complexant A:(g/L) 1; accelerant B: (g/L) 0.15; Na₂MoO₄:(g/L)0.1;...