A controllable fabrication strategy of anodic oxides film with dense, nano-porous and open-top ordered porous arrays morphology on 304 stainless steel in fluoride-based ethylene glycol electrolyte

Abstract

A facile anodizing strategy without using perchloric acid was reported in this work to controllably produce three different types of self-organized structure anodic oxides films with dense, nano-porous and open-top ordered porous arrays structure morphology. These oxides were developed on 304 austenitic stainless steel (SS) substrate in fluoride-based ethylene glycol electrolyte by simply regulating the H2O concentration in the electrolyte and anodizing voltages. From our analysis, it was found that the above-mentioned anodizing parameters significantly affect the morphologies of the anodic oxides film rather than the chemical composition. The chemical compositions of the different types of films were α-Fe2O3 and Cr2O3 or (FexCr1-x)2O3 composite oxides. Moreover, the higher (70 V), middle (50 V), and lower voltages (30 V) were respectively suitable for the preparation of the dense, nano-porous, and open-top ordered porous arrays morphology structure anodic oxides film due to the different anodized film formation rate, respectively. Finally, a plausible formation-dissolution mechanism was provided by considering the dissolution effect with the assistance of the oxygen evolution derived from H2O, which is favourable to form the sparser anodized film on the SS substrate. In addition, the anodizing parameters selected principle for the corresponding anodic oxides layers with different morphologies onto the SS substrate. The controllable fabrication strategy of the various film will greatly broaden the application of the SS substrate in both anti-corrosion and decoration fields.