| In this thesis,the influence of additives,technological parameters such as oxidation time,temperature,current density,concentration of sulfuric acid solution and sealing process on the film thickness,hardness and corrosion resistance of the anodic oxidation films prepared in sulfuric acid solution were discussed.The phase composition,surface morphology,surface hardness and corrosion resistance of the samples anodized under different process parameters were characterized by using X-ray diffraction(XRD),scanning electron microscope,microhardness tester and electrochemical workstation.The results showed that:(1)The corrosion resistance of the oxide film prepared with different additive combination was superior to the original oxide film prepared without additive when the sulfuric acid solution was choosed as the base electrolyte,and the best additive combination was "boric acid + citric acid + glycerol +lanthanum sulfate".(2)With the optimum additive combination mentioned above,the anodic oxidation process parameters to obtain a film with relative good corrosion resistance was as follow:oxidation time with 50 minutes,current density of 2.5 A/dm2,sulfuric acid concentration of 20 wt.%and oxidation temperature at 10 ℃.(3)The corrosion resistance of the oxide films were tested by various techniques,the results showed that:the films sealed with cerium salt at high temperature exhibits better corrosion resistance than that sealed with other sealing methods,and the corrosion current desist is 0.045 A/dm2.The oxide films sealed with different methods showed corrosion resistance in such an order:cerium salt sealing at high temperature>boiling water sealing>room temperature sealing>cerium salt passivation sealing.(4)Although the sulfuric acid anodizing process developed in this thesis can obviously improve the corrosion resistance of the alloy,the surface hardness and wear resistance of the alloy were decreased at the same time.Therefore,in order to obtain a good comprehensive performance,the current anodic process still needs further more improvements. |
