Technical And Performance Study Of Chromate-Free Chemical Oxide Film On Aluminum Alloy

This work studied a chromate free coating system based on zirconate and permanganate. The orthogonal test was used to optimize the bath formulation and treatment procedures. High corrosion resistance chemical oxide films were formed on the surface of the LY12 aluminum alloy. In addition, this paper discussed morphology and composition of the oxide films through SEM technology. And the valence states of the key elements in the oxide film have been studied via XPS analysis.In this paper, the corrosion resistance of the oxide film has been investigated with electrochemical technology and other conventional methods. Moreover, the influences of several seal post-treatments on performance and morphology of oxide film were also studied through electrochemical polarization technology. The results indicated that the F-Ni and boiling water treatment was the best post-treatment technology.The SEM analysis shows that the samples with 'dual seal' treatment have thicker and more compact oxide film, and the triangular prism particles were formed on the surface of the films.This paper also discussed the impact of permanganate and zirconate in oxide solution on the structure and the performance of the oxide film. The results indicate that with the increase of the zirconate, the growth of the particles shows opposite order on the oxide films with boiling water treatment and the films with F-Ni and boiling water treatment. The forming of tile-like particles on the oxide film without and the oxide film with boiling water treatment is due to the Horizontal growth rate is much greater than vertical growth rate after the change of the permanganate concentration.