Study On Preparation Process Of Anodized Layer On Carbon Steel Surface

Electrochemical anodization is one of the simple and effective techniques for directly synthesizing morphologically controllable nanostructured films on metal substrates.Nanostructured iron oxide(α-Fe2O3)has the advantages of low band gap,low cost and high chemical stability.The nano-morphology can also increase the specific surface area of the oxide film.Therefore it has been applied to water decomposition and photocatalysis,photocathode protection and supercapacitor and other fields.Compared with pure iron to prepare nanostructured oxide film by anodizing,steels have the advantages of abundant raw material sources,relatively low price,and mature production technology.Therefore,steels could become materials with great development potential and application prospects after anodization.In addition to iron,steels also contain other elements including carbon,chromium,nickel and so on.Through different heat treatment processes to control the distribution of elements and the existence of compounds,different metallographic structures can be prepared to adjust the physical and mechanical properties of the material.On the other hand,there is a lack of reports on the influence of the distribution of elements and the metallographic structure on the microstructure and application performance of the anodic oxide film in the current research on steel anodization.Therefore,this paper selects carbon steels with relatively simple composition as the research object,anodizes the metallographic carbon steel matrix with different distributions and existing forms of carbon elements prepared by different heat treatment processes.The relationship between the morphology and microstructure of the oxide film was analyzed.The effects of carbon distribution and microstructure on the electrochemical properties of the oxide film were discussed.The results show that:(1)the anodized iron oxide films were inherited from the microstructural characteristics of the original metallographic structure by employing metallographic regulation.Different characteristics of the original metallographic structures could affect the rate of the anodization reaction and determine the thickness and nanopore size of the oxide layer on the substrate.(2)the annealing temperature directly affects the morphology of the carbon steel anodized film,and the lower annealing temperature(at 300℃)can maintain the nanometer morphology and undergo a crystalline transformation to obtain iron oxide.(3)The carbon steel oxide film with better nano-morphology uniformity has better electrochemical performance.The distribution and existence of carbon elements directly affect the nano-morphology of the oxide film layer,which indirectly affects the electrochemical performance of the porous oxide film.Due to its low carbon content,mainly in the form of solid solution and good uniformity of oxidation film,the quenched low carbon steel has the advantages of high specific capacitance,low charge transfer resistance and good cycle stability required for supercapacitors.In summary,it was revealed the microstructure of anodized oxide film on carbon steels could be effectively regulated by tuning the original microstructure and then adjust the application performance of the oxide films with the conventional heat treatment.The methodology and techniques could be transplanted into similar alloy systems for the designing and implementing of advanced functional oxide layer by anodizing method.