Preparation Of TA2 Pure Titanium Anodized Film And Its Corrosion Resistance

The excellent corrosion resistance of titanium and titanium alloys is due to the oxide film formed on the surface.Under normal conditions,the oxide film formed is thin and uneven,and the weak point above it is easy to become the origin of corrosion.Anodic oxidation technology can form a layer of anodic oxide film that is more dense,thicker than the natural oxide film on the surface of titanium and titanium alloy,which is a widely used to increase the thickness and corrosion resistance of the film.The thickness,uniformity and other characteristics of the anodic oxidation film have an important relationship with a variety of oxidation conditions and parameters,and these characteristics in turn affect the anodic oxidation film corrosion resistance.However,the effect of various anodic oxidation parameters on the corrosion resistance of the oxide film in different electrolyte systems is not very clear.Therefore,it is necessary to understand the influence of various parameters and conditions on the anodic oxide film,which is of great significance for the preparation of titanium anodic oxide film with the expected structure and properties.In this paper,titanium anodic oxide films were prepared in sulfuric acid electrolyte,sodium tartrate electrolyte and ammonium fluoride glycol electrolyte respectively.The oxide film was characterized by SEM,AFM,XPS,Raman test and electrochemical test.The formation process of titanium anodic oxide film was obtained.On the basis of this,the influence of potential,electrolyte concentration and time on the corrosion resistance of the oxide film in different electrolyte systems was studied.The corrosion resistance of the oxide films formed in the three kinds of electrolyte systems was further compared.Finally,the corrosion process of the anodic oxide film in NaCl solution was briefly analyzed.The results showed that the anodic oxide film is formed in a very short time.The formation of oxide film was a dynamic process of growth and dissolution,the ion current and electron current in the film led to the growth and dissolution of the oxide film,respectively.The presence of electronic current means that the release of oxygen.The escape of oxygen bubbles can be used as embryo to form holes,thus the formation of porous oxide film.The nanotube film was self-organized and ordered to grow on the basis of porous membrane.in the sulfuric acid electrolyte,the corrosion resistance of the oxide film increases with the increase of the oxidation potential.The oxidation degree of the oxide film obtained at the high potential of 50 V is higher,and has the maximum thickness calculated value of 64 nm.The protective effect on the film is better.In the sodium tartrate electrolyte,the electrolyte concentration is too high,the solute ion aggregation,the overall degree of oxidation of the film is not uniform;electrolyte concentration is too low,the oxide film growth is not complete;both will lead to lower corrosion resistance of the oxide film.The results showed that the anodic oxide film obtained at 20 min and 15 g/L has the advantages of small size,uniformity,low roughness,complete growth of the film and the widest passivation interval(0V?4V).The corrosion resistance was the best.In ammonium fluoride glycol electrolyte,adding a small amount of hydrochloric acid,the chemical etching rate was accelerated,Which avoided the phenomenon of nozzle clogging caused by infinite extension of nanotubes and formed two-layer structure oxide film of porous titanium nanotube array.The top of the nanotube tube wall was thinner and the bottom of the nanotube tube wall was thicker,showing a"V"-shaped distribution,which has a better protective effect on the titanium matrix.The morphology and corrosion resistance of the oxide films formed in the three electrolytes were compared.A porous oxide film was formed in the sulfuric acid electrolyte;the surface of the oxide film obtained in the solution of sodium tartrate was ruptured and the petaloid drum tissue;An oxide film of porous titanium nanotube arrays of double-layer structure morphology was obtained in ammonium fluoride electrolyte.The oxide film obtained in the sodium tartrate electrolyte was more densely than the oxide film formed in the other two electrolytes,the corrosion resistance was better.The polarization resistance of the oxide film could reach 3.38×10~6?,which had a better protective effect on the substrate.The corrosion of the titanium anodic oxide film in NaCl aqueous solution was closely related to Cl-.Some defects(such as pits)in the surface of the oxide film will be destroyed by the intrusion of Cl-,leading to the formation of corrosive pores.When the adjacent holes were interconnected by corrosion,they formed microcracks.