Abstract: A novel formation process of chromium-free Mn(VII)-Ti(IV) conversion film on 6063 aluminum alloy was explored. Potassium permanganate and titanyl sulfate were used as main ingredients of the passivator. The parameters of film-forming process, such as temperature, reaction time, pH value and bath composition, were investigated, and the process was optimized by the orthogonal experiments. The surface morphology and element constituents of the chemical conversion film were analyzed, respectively, and its corrosion resistance was investigated by simply chemical analysis methods, such as the CuSO4 solution dripping and seawater corrosion tests. The optimum formulation was KMnO4 5 g/L, TiOSO4 2 g/L, NaF 0.05 g/L and ZnSO4 0.3 g/L, and the optimum conditions were temperature 50℃, reaction time 15 min and pH value 2.7. The results showed that a golden chemical conversion film with mass about 589 mg/m2 could be obtained. The main elemental constitutes of the conversion film were O, Mn, Al, Zn and Ti. The Mn(VII)-Ti(IV) conversion film had better corrosion resistance performance than hexavalent chromium conversion film in the CuSO4 solution dripping test, and had similar performance with hexavalent chromate conversion film in the seawater.

Key words: aluminum alloy, chromate-free conversion, Mn-Ti system, conversion film, corrosion

摘要： 以KMnO4和TiOSO4为钝化剂主要成分，研究6063铝合金锰(VII)-钛(IV)系钝化成膜新工艺，考察钝化液成分、温度、pH值、反应时间对成膜过程及膜耐腐蚀性能的影响，并通过正交实验优化工艺方案，分析转化膜的形貌和化学组成，采用化学方法考察化学转化膜的耐蚀性能. 结果表明，最佳钝化液配方为：KMnO4 5 g/L, TiOSO4 2 g/L, NaF 0.05 g/L, ZnSO4 0.3 g/L. 在钝化温度50℃、钝化时间15 min及pH值2.7的最佳工艺条件下，锰(VII)-钛(IV)系钝化工艺制备的化学转化膜为金黄色，膜质量为589 mg/m2，膜主要由O, Mn, Al, Zn, Ti组成. 锰(VII)-钛(IV)系钝化新工艺环境友好，所制化学转化膜耐CuSO4点滴腐蚀性能优于Cr(VI)转化膜，耐人造海水腐蚀能力与Cr(VI)转化膜相近.

关键词: 铝合金, 无铬钝化, 锰-钛系, 化学转化膜, 腐蚀