Post-Processing And Passivation Of Hot-dip Aluminum With One Flux Bath Method

In the procrss of hot dip aluminizing with the one flux bath method, there are dirts and fluxes composed of KCl-NaCl-NaF-AlF3 on the surface of aluminum coating, which make the appearance of the aluminum production undecorated, and have some corrsion for the aluminum coating. So that,. These dirts and fluxes must be cleared, and do some passivation on the aluminum coating. In the process of passivation, the toxic wildly used chromate not only endangers humans, but pollutes the enviorment. So the research on the hot dip aluminuming without chromium in the passvation is imperative.The study systematically has incestigated the post-procesing of hot dip aluminum and tha passvation without chromium, and prepared more available post-processing liquid and passvation liquid without chromium, compared the surface morphology of samples with new or traditional post-processing, and their effectiveness of corrsion resistance. With observing and analyzing the component and structure of the molydate passivation film, and discusse the mechanism of filming and anticorrsion; even compare the corrsion resistance of passivating film by the salt spray test, saline immersing test and electrochemical test.According orthogonal test the optimum range of the post-treatment agent formula is determined:The concentration of HNO3 and HF is 5%-10%, and 0.25%-1.5%.and the concentration of surfactant A and B is 0.10-0.15g·L-1 and 0.05-0.15g·L-1, the passivae time is 60s, with optimum addition.Compared to tradtional post-processing liquid, the salt on the surface of sample being new post-processed has reduced at lest 2/3, according the result of surface scan. The result of the fixed and alternative damp heat test shows:the salt removing of the sample with new post-processing is better than the traditional one.The corrsion resistance of the sample with molybdate passivation is better than the one without passivation, according the salt spray test, saline immersing test and electrochemical test. In theory, the passive film resists the corrsion and delays the rusting as a physical barrier on the surface of aluminum coating, that evidently enhance the resistance corrsion.