黄铜表面富植酸钝化工艺研究

采用植酸(50%,质量分数)8 ml.L-1,双氧水(30%,质量分数)30 ml.L-1,硼酸5 g.L-1,聚乙二醇15 ml.L-1,添加剂4 g.L-1钝化液对冷轧HAl72-2.5-1黄铜带材进行钝化处理,探讨工艺条件(钝化温度、钝化时间和钝化液pH值)对富植酸钝化膜耐蚀性的影响。通过硝酸溶液点滴腐蚀试验对黄铜表面富植酸钝化膜的耐腐蚀性能进行研究。结果表明,富植酸钝化膜的最佳工艺条件为:钝化温度范围是35～40℃,pH值为2.5,钝化时间为60 s。SEM微观形貌显示,膜层表面平整,结构致密。失重试验结果表明:经富植酸处理的试样的平均腐蚀速率为0.0054 g.m-.2h-1,与重铬酸盐处理的试样的平均腐蚀速率(0.0040 g.m-.2h-1)相当,比未经钝化处理的试样的腐蚀速率(0.0376 g.m-2.h-1)低的多,说明采用富植酸钝化处理能对合金材料起到很好的保护作用。经过12 h的盐雾法试验显示:经重铬酸盐处理的试样表面有较多的褐色斑点,表面颜色不均匀,而经过富植酸处理的试样表面为金黄色,只有少量的腐蚀斑,说明采用富植酸处理的试样比采用重铬酸盐处理的试样具有更好的抗变色能力。富植酸钝化液中不含铬,废液中不会产生铬污染。

Passivation Technology Research of Rich-Phytic Acid for Brass-Strip

The effect of passivation conditions(temperature,passivation time and pH value of passivation solution) on the corrosion resistance of passivation film treated by passivator of rich-phytic acid(50%,mass fraction) 8 ml · L-1,hydrogen peroxide(30%,mass fraction) 30 ml · L-1,boric acid 5 g · L-1,polyethylene glycol 15 ml · L-1,additive 4 g · L-1 was investigated.Samples were made of cold-rolled strip of HAl72-2.5-1 alloy.The corrosion resistance of passivation film was detected by nitric acid dripping.The results showed that the optimum condition of passivation by rich-phytic acid passivation solution was at the range of 35~40 ℃,pH 2.5 dipping for about 60 s.Photos of SEM showed that the passivation film was uniform and compact.The weight loss test showed that the average corrosion rate of samples treated by rich-phytic acid passivator was 0.0054 g · m-2 · h-1,that was equal to the rate(0.0040 g · m-2 · h-1) of dichromate treated samples,and much lower than the corrosion rate(0.0376 g · m-2 · h-1) of samples without passivation treatment.It meant that rich-phytic acid passivator protected brass strip well.12 h of salt spray test showed that the dichromate treated samples changed brown with a lot of corrosion spots,and rich phytic acid treated samples turned to golden yellow with only a few spots.It showed that brass strip processed by rich phytic acid had better anti-color capability than those dichromate treated samples.The rich phytic acid passivator was environment protection without chromium ions.