Research Of Limits Coating Capacity Of Ti-Zr Conversion Coating Solution On Aluminum Alloy Surface

As we all know, Ti-Zr conversion coating is one of the most promising surface treatment techniques instead of chromate conversion coating. Ti-Zr conversion coating has been tending to be mature, especially our teams have obtained good comprehensive properties of Ti-Zr conversion coating through continuous exploration. But at present the research about the limits coating capacity of the treatment solution are barely, in order to promote its application in industrial. On this basis, the research in this thesis was focus on limits coating capacity of the treatment solution at room temperature under the process of repeated use.At the same time,the main purpose is to studying the change rule of group composition and performance of the conversion coating. Through real-time monitoring the change of solution composition, conductivity and PH value, in order to research the stability of the treatment solution.In strict accordance with the actual working conditions at room temperature, the forming area of solution in determining surface area/volume ratio under continuous coating test is about 1.73m2. Making Coating binding force as the evaluation criteria, the forming area of solution in determining surface area/volume ratio is about 1.15m2. The solution pH value has a steadily rising trend under continuous coating test, but the range of the rising is not large. But the solution conductivity has a steadily declining trend, from the initial 3.83 ms/cm to failure as 2.61 ms/cm.With the increase of number of processing, corrosion resistant performance of the optimal coating is constantly falling, its anti-corrosion time was reduced to 41 s from the initial 234 s, and corrosion current density increased by more than 17 times. According to the result of SEM/EDS analysis, the film was thin, many visible scratches and corrosion pit are found on the coating surface. Also it was found the content of Ti, V and Zr was poor in the coating.In the experiments of components of solution adding in, adding six fluorine titanate causes a linear growth for the electrical conductivity of solution, and complexant adding did not improve the conductivity of solution, instead of falling slightly, but according to the principle of electrical conductivity, it can be estimated that The complexation reaction has been happened between the complexing agent and metal ions. The change of electrical conductivity of solution appears similar to parabolic rule by adding oxidant. The redox reaction happened between the complexing agent and oxidant. The coordination reaction that happened between the complexing agent and MO²⁺was to form the stable complex molecules or ions. Through the analysis of single factor experiment, the order of component adding will not affect the electrical conductivity of solution. The result of anti-corrosion showed that the concentration of Zr⁴⁺ and oxidant significantly effect the performance of corrosion resistance...