Technology Research Of Nano-porous Film On Stainless Steel Fabricated By Anodizing

Nano-porous anodic film on stainless steel surface is mainly used as functionalnano-materials for biomedical, electronic equipment, home decoration and other fields.The study of nano-porous anodic film on aluminum and titanium surface has beenrelatively mature at home and abroad, but aluminum is relatively soft, leading to itsapplication is limited; titanium is relatively expensive; stainless steel has goodmechanical properties and cheap, so there is a greater application prospects. Currently,the preparation process of anodizing and forming mechanism of nano-porous film aremostly made of aluminum or titanium. The theoretical research specifically fornano-porous anodic films on stainless steel surface is relatively small, and it is notsystematic.In this paper, nano-porous film with different structures was fabricated on threedifferent types of stainless steel surfaces by anodizing. The nano-porous film wasanalyzed by scanning electron microscopy, X-ray photoelectron spectroscopy andcurrent-time curve. It was discussed that the relation about anodizing parameters(oxidation voltage, oxidation time, oxidation temperature, type and concentration ofelectrolyte) with nano-porous film morphology and structure. Thereby formingmechanism on nano-porous film was studied. The results were as follows:904L superaustenitic stainless steel was anodized in in ethylene glycol electrolytecontaining10vol%perchloric acid. Average pore size of the nano-porous anodic filmgradually increases with increasing oxidation voltage. When the oxidation voltage ishigher than40V, average pore size continue increases, but the characteristics of rules and orderly on nano-porous anodic film is destroyed. Initially, average pore size of thenano-porous anodic film gradually increases and morphology is gradually regular withincreasing oxidation time. After600s, the morphology is no longer change withextending oxidation time. High temperature is not conducive to forming of regularnano-porous film, the optimum oxidation temperature is4℃in this experiment.The thin nano-porous film of small pit structure is fabricated in electrolyte solutionof perchloric acid that its PH value is1. There is little change for the morphology ofnano-porous film when the electrolyte concentration has a small range of change. Themajor component of anodic film is Cr2O3. The transpassive dissolution is more likely tooccur on stainless steel containing more Cr at higher voltage. The thick nano-porousfilm of nanotube structure is fabricated in electrolyte solution of ammonium fluoridethat its PH value is5-6. The anodic film is sensitive to the electrolyte concentration. Thefilm is brittle and readily soluble in distilled water. The major component of anodic filmis a compound of iron and fluorine. The grown of nano-porous film consists of grownby oxidation and acid dissolution. So the thicker nano-porous film is easily formed inweakly acidic electrolyte that its PH value is higher.