The Study On The Maximum Formation Ability Of Ce-Mn Conversion Coating Passivation Solution On6063Aluminum Alloy

Rare earth conversion coating of aluminum alloy is one of the most promising surfacetreatment technologies which can replace the chromate conversion coating at present. Butmost of the rare earth conversion coatings still have some shortcomings, such as, longprocessing time, complex process, and high processing temperature. Some technologies canform coatings rapidly at room temperature by adding stabilizing agents, accelerating agentsand other additives. But the passivation solution is very sensitive to the externalenvironmental factors and has poor stability. Besides, there is a negative correlation betweencoating forming rate and stability. So these factors limit the industrialized popularization andapplication of rare earth conversion coating. Our research group has developed the Ce-Mnconversion coating which can form at room temperature and the treatment solution is stability.In this basis, the pre-treatment process for aluminum alloy Ce-Mn conversion coating, thestability of passivation solution and the maximal film-forming ability of passivation solutionwere studied in this paper.Through the maximal film-forming ability tests under the three pre-treatment processes(first acid after alkali, first alkali after acid, two-step pickling) found that the maximalfilm-forming ability of passivation solution in the three pre-treatment process conditions hasthe same area of film-forming. However, the pre-processing of the two-step pickling processcan make the corrosion resistance of the continuous conversion coating more stable.Under the best pre-treatment condition, began the maximal film-forming ability test withthree kinds of different film-forming amount (720cm~2/L/h,1440cm~2/L/h,2160cm~2/L/h) andfound the maximal film-forming ability of the passivation solution had not changed withthe difference of the film-forming amount, but using a smaller film-forming amount canincrease the stability and the corrosion resistance of the continuous conversion coating. Adding double acid stabilizer to the passivation solution, the film-forming ability of thepassivation solution increased by70%, and the corrosion resistance of the conversion coatingwas more stable, but the time of film-forming was extended and the corrosion resistance ofthe coating was overall decreased compared with the coating without adding stabilizer.