Study On Preparation And Corrosion Resisitance Of Zeolite Films/Cortings On Aluminum Alloys Surface

In practical use,aluminum alloys are often damaged by corrosion,affecting the ir performance and service life.Zeolite molecular sieves are a kind ofhighly uniform molecular-scale micropores(3-12?)materials.The studies have shown that templated zeolite molecular sieves exhibit excellent,environment-friendly corrosion resistance.In this paper,ZSM-5 zeolite film/coating and iron-doped ZSM-5 zeolite film were successfully prepared on the surface of aluminum alloys by improving the surface state of aluminum matrix.The influence of surface state,synthetic mode on the formation process of the zeolite film were analyzed by X-ray diffraction,scanning electron microscopy,polarization curve and salt spray corrosion test,the zeolite film/coating layer with good surface adhesion and excellent corrosion resistance was obtained.Chemical polishing,anodizing and other surface treatments on the surface of aluminum alloy samples were carried out.The results showed that the structure of the anodic oxide film on the aluminum alloy surface was highly ordered and the electrochemical performance was good at 15?.After the ZSM-5 zeolite film was deposited on the anodized sample,the synergistic effect of the anodized film and the zeolite film effectively blocked the contact between the corrosive medium such as Cl~-and the substrate surface,thereby slowing the corrosion rate of the aluminum alloy.The effects of synthesis methods and conditions on the synthesis of ZSM-5zeolite membranes were emphatically investigated.The optimum conditions for the synthesis of ZSM-5 zeolite film are obtained:crystal seed method,crystallized 10h,the crystallization temperature was 180?.Under this condition,the size of the ZSM-5 zeolite was uniform,the size was about 0.5?m,the deposited zeolite film had no defect,the film was continuous and intac,and it was firmly bonded to the surface of the aluminum matrix.Electrochemical test results showed that the corrosion potential of the ZSM-5 zeolite film was-0.569 V and the corrosion current density was reduced by two orders of magnitude,demonstrating excellent corrosion resistance.The heteroatom Fe was introduced into the molecular sieve framework.The optimum synthesis conditions of Fe-ZSM-5 zeolite film were found:crystal seed method,Si/Fe ratio was 80,the ratio of raw material was aluminum nitrate:Tetrapropylammonium hydroxide:ethyl orthosilicate:iron nitrate:deionized water=0.0025:0.36:1:0.0125:90,aged 24 h.The prepared Fe-ZSM-5 zeolite had good cross-linking degree and high uniformity,and the zeolite film was continuous and dense without defects.After entering into the zeolite framework,the heteroatom Fe completely existed in the Si-O-Si skeleton.The best ratio for preparing the ZSM-5 zeolite coating was 11wt%molecular sieve added to the aqueous adhesive.The zeolite coating had good uniformity and excellent corrosion resistance after immersion corrosion test.The study found that when the concentration ratio was high,the coatings exhibited better anti-corrosion performance;when the proportions were low,the anti-corrosion performance was even worse than the coating without zeolite,indicating that the low concentration of zeolite was not conducive to improving the anticorrosion performance.