镁合金表面无铬化学转化处理液工艺参数最佳范围的研究

Study on the Optimum Range of Technical Parameters of Chromium-free Conversion Treatment Solution for Magnesium Alloy

为了确定能获得性能优良转化膜的处理液的工艺参数最佳范围，研究了一种新型镁合金处理液的酸度比、pH值与转化膜质量的关系。试验表明：随着处理镁合金的表面积增加，处理液总酸度增加，游离酸度减小，处理液pH值与酸度比都增高。利用扫描电子显微镜（SEM）分析不同酸度比处理液处理所得的转化膜形貌可知：酸度比过高与过低的处理液都不能形成完整的转化膜，当处理液酸度比在8，2～9．4的范围内时，能够得到均匀完整的转化膜，72h的盐雾试验表明，酸度比在8．2—9，4范围内的处理液处理所得的转化膜的腐蚀面积较小。

In order to know the optimum range of technical parameters of chromium-free conversion treatment solution which produce good quality coating, a new conversion treatment solution for magnesium alloy was analyzed, the relation between the acidity ratio as well as pH value and conversion coating quality was researched systematically. The results demonstrate that the values of total acidity and pH increase with the increase of the area of magnesium alloy specimen treated in solution. However, the value of free acidity is just the reverse. The surface morphology of conversion coating produced by treatment solution with different acidity ratio had been studied by means of SEM. The results indicate that the conversion coating treated by solution with too high and low acidity ratio is not completed and the uniform and complete conversion coating will be produced on condition that the acidity ration of treatment solution ranged from 8.2 to 9.4. Morever. Its corrosion area ratio is low based on the results of 72h salt spray testing.