铝及铝合金无铬氟锆酸盐化学转化膜

Chromium-free fluorozirconate-based chemical conversion coatings on aluminum and aluminum alloys

研究了一种适用于铝及铝合金的无铬化学转化工艺,探讨了转化液的主要成分和工艺条件对转化膜质量的影响,得到了较好的工艺条件:氟锆酸钾1.0～2.0g/L,氢氟酸0.5～1.5mL/L,促进剂4～6g/L,氧化剂(硝酸镁)8～12g/L,pH3.5～4.0,温度40～60°C,氧化时间4～6min。按此工艺制备的转化膜均匀致密,呈彩虹色,色泽鲜艳,附着力1级,在35°C、5%(质量分数)的氯化钠溶液中的腐蚀速率为0.01989g/(m2·h),与铬酸盐钝化膜的耐蚀性相当。喷涂在该转化膜上的漆膜,当中性盐雾试验进行至240h时,仍无脱落。

A chromium-free chemical conversion process suitable for aluminum and aluminum alloys was studied. The effects of main components and process conditions on the quality of conversion film were discussed. The optimal process conditions were obtained as follows：potassium fluorozirconate 1.0-2.0 g/L,hydrofluoric acid 0.5-1.5 mL/L,accelerant 4-6 g/L,magnesium nitrate（as oxidant） 8-12 g/L,temperature 40-60 °C,pH 3.5-4.0,and oxidation time 4-6 min. The conversion film obtained from the process is uniform and compact,presents an iridescent color with bright luster,and has a adhesion strength of 1 grade and a corrosion rate of 0.019 89 g/（m2·h） in 5wt% NaCl solution at 35 °C,showing similar performance to chromate conversion film. The coating sprayed on the conversion film dose not fall off after neutral salt spray test for 240h.