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采用不同的植酸水溶液对压铸镁合金AZ91D进行化学转化处理,通过SEM、EDS、浸泡法研究了添加剂及pH值对转化膜膜厚、形貌及耐蚀性能的影响。结果表明:pH值由3增大到5时,转化膜的膜厚和耐蚀性呈先增大后减小的趋势,当pH=4时膜厚达到最大值,且耐蚀性能最好。加入添加剂后所得到的化学转化膜的膜厚和耐蚀性能都相对未加添加剂的化学转化膜有所增大,同时加入添加剂后的转化膜表面裂纹明显变小。在选用Ca(NO3)2、偏钒酸铵、酒石酸钠作添加剂的植酸溶液中所形成的转化膜的性能最佳。
The effects of additives and pH value on the film thickness, morphology and corrosion resistance of the conversion coating were studied by SEM, EDS and immersion methods using different aqueous solution of phytic acid to transform the die-casting magnesium alloy AZ91D. The results show that when pH value increases from 3 to 5, the film thickness and corrosion resistance of the conversion coating first increase and then decrease. When the film thickness reaches the maximum at pH = 4, the corrosion resistance is the best. The film thickness and corrosion resistance of the chemical conversion coating obtained after the addition of additives are all increased compared with those of the unadhered chemical conversion coating, and the cracking of the conversion coating after the addition of additives is significantly reduced. In the selection of Ca (NO3) 2, ammonium metavanadate, sodium tartrate as additive phytic acid solution formed the conversion performance of the film.