Effect Of Al-Re Master Alloys On Corrosion Properties Of Zn-Cu-Ti Alloys

Compared with metal zinc,Zn-Cu-Ti alloy not only has excellent corrosion resistance,but also has better mechanical strength.Using the alloy sheet instead of the traditional galvanized sheet as the roof covering material can prolong its service life by dozens of times,and has the advantages of recycling and environmental protection.Zn-Cu-Ti alloy is widely used in construction industry.With the development of human living environment from ordinary atmosphere to acid rain,haze and other extreme environments,the requirements for corrosion resistance of building materials are constantly increasing.Therefore,the study of corrosion performance of Zn-Cu-Ti alloy under extreme environment is the key to expand the application of this alloy.In this paper,different Zn-Cu-Ti-Al-RE multi-element alloys were designed.First,Zn-Cu-Ti alloy was prepared by vacuum melten,and then Al-RE(Ce,Nd)intermediate alloy was added by melting method.The preparation techniques of the alloy components at similar melting and boiling points were studied,and explore the microstructure and mechanical properties of the alloy through metallographic observation,phase analysis and hardness test.The corrosion resistance of each group of alloys was tested on the basis of the microstructure and mechanical properties meeting the requirements of building materials.In addition,the corrosion resistance of prepared multi-element alloys in neutral salt solution,acid rain simulation solution and alkaline seawater simulation solution was systematically evaluated,and the corrosion rules are determined and the corrosion mechanism is discussed,which provides experimental basis for the application of Zn-Cu-Ti alloy in extreme corrosion environment.It was observed that after adding Al-RE,the grain size of Zn-Cu-Ti alloy was further refined and the phase distribution was more uniform,but excessive addition of rare earth will accumulate on the grain boundary,which will have a negative impact on the uniformity of the structure.Among them,the chemical properties of Ce are active,and it is easy to spontaneously aggregate to form massive phase,and the enrichment effect appears in some areas of grain boundary under internal force.In comparison,Nd is chemically more stable and tends to form small sized granular compounds,and it can be distributed more evenly.The hardness of all the alloys increased slightly,which could be attributed to the effect of fine grain strengthening and dispersion strengthening.However,the hardness of the alloy was slightly reduced by adding excessive Al-Ce intermediate alloy.The corrosion morphologies of the prepared multi-element alloys are quite different in three typical simulated solutions:neutral,acidic and alkaline,the order of corrosion degree from big to small which were serious general corrosion in acid rain simulation solution,slight general corrosion and serious localized corrosion in neutral salt simulation solution,slight general corrosion and minimal pitting in alkaline seawater simulation solution.Among them,the corrosion mechanism is mainly the adsorption and destruction of Cl~-in neutral salt solution,and adding Al-Ce to Zn-Cu-Ti alloy can improves the formation rate of the passive film,but also prevents Cl~-from adsorbing on the surface of the alloy,so the corrosion process is suppressed to some extent.In contrast,the addition of excessive Al-Nd tends to form complex compound phases,resulting in electrochemical inhomogeneity on the alloy surface,which leads to severe corrosion in later stages.In acid rain simulated solution,the main corrosion mechanism is the synergistic effect between Cl~-and H~+,the corrosion of the alloy after adding Al-RE is relatively serious,and the corrosion resistance decreases with the increase of the addition.In the simulated solution of alkaline seawater,the main corrosion mechanism is the adsorption of ions competes with Cl~-and OH~-.in this solution,the corrosion layer formed by the alloy has higher density,faster growth rate and higher stability,and the addition of Al-Nd intermediate alloy can improve the corrosion resistance of the alloy and effectively reduce the tendency of pitting corrosion.