Anodizing Process And Corrosion Resistance Of Zinc-copper-titanium Alloys

Zinc-copper-titanium alloy(also called titanium-zinc sheet)has good ductility,creep resistance,machining performance and corrosion resistance.It is often used to decorate exterior walls and roofs of high-end buildings and has high economic value.Although my country has a large number of high-quality zinc resources,the development and production of wrought zinc alloys(including zinc-copper-titanium alloys)are far behind developed countries in Europe and America.At present,there are very detailed studies on the alloy composition,mechanical properties and machining properties of zinc-copper-titanium alloys at home and abroad.Considering that zinc-copper-titanium alloys are mainly used as building decoration materials and are used in roofs or exterior walls and other fields,they need beautiful colors and surface treatment is necessary.At present,the surface treatment process of zinc-copper-titanium alloys is blocked and kept secret in foreign countries.The treatment process results in a thinner treatment layer,which cannot meet environmental erosion.This paper takes zinc-copper-titanium alloy as the research object,adopts anodic oxidation process for surface treatment,clarifies the corrosion mechanism of zinc-copper-titanium alloy.Which not only enriches the surface treatment process of non-ferrous metals,but also breaking the foreign technological blockade against our country and increasing the added value of zinc alloy production are of great significance and social value.First of all,this thesis takes zinc-copper-titanium alloy as the research object.Through orthogonal experiments,the appearance and morphology of the anodic oxide film of zinc-copper-titanium alloy under different oxidation temperature,oxidation time,current density and sodium hydroxide concentration are studied.The process plan with the best appearance,and the appearance,microscopic morphology,corrosion resistance and corrosion products of the zinc-copper-titanium alloy after anodizing treatment have been studied.At the same time,theoretically,the oxygen on the zinc surface during the anodization treatment The adsorption process was calculated and the following conclusions were obtained:(1)Orthogonal experiment results show that the best anodizing process plan is:A₁B₁C₃D₃,that is,the electrolyte sodium hydroxide content is 10g/L,the oxidation current density is 5A/dm²,the oxidation time is 30min,and the oxidation temperature is 40?.The main component of the anodic oxide film is zinc oxide,and the white and black areas in the micro morphology represent the different content of zinc oxide.The larger the zinc oxide content,the white in the micro morphology.(2)Analysis of microscopic morphology and electrochemical results found that the thicker and smoother the oxide film surface layer,the better the corrosion resistance;the rougher the oxide film surface,the more holes and the more cracks and the worse the corrosion resistance.Through the analysis of the AC impedance equivalent circuit,it is found that the film resistance R_t representing the anodic oxide film is much greater than the charge transfer resistance R_c,which indicates that the anodic oxide film contributes more to the corrosion resistance.(3)The simulated seawater immersion test and salt spray test found that the zinc-copper-titanium alloy after anodizing treatment appeared white rust later than the unprotected zinc-copper-titanium alloy and had better corrosion resistance.The main corrosion products were zinc oxide and basic Zinc chloride(the main product of the salt spray test is also basic zinc carbonate).After 120 hours of the simulated seawater immersion test and salt spray test,the corrosion products are covered on the surface of the sample,the corrosion rate is slowed down,and the surface of the sample is not obvious The change.(4)The stable adsorption positions of oxygen atoms on the zinc(0001)surface are the FCC position and the HCP position,and the HCP position is more stable than the FCC position,and the adsorption energy of the HCP position is more negative than that in the FCC;the zinc(0001)surface adsorbs oxygen After the atoms,there is a dipole moment on the surface,and the work function of the system becomes larger.The work function of the system is the highest when oxygen atoms are adsorbed at the FCC position,which is 4.362 eV.The 4s orbital and 3d of the zinc atom are hybridized with the 2p orbital of the oxygen atom,the electrons in the zinc atom are transferred to the oxygen atom,and an adsorption bond is formed between them.