Self-organised nanoporous anodic films on superaustenitic stainless steel

Abstract

Self-organised nanoporous anodic films were fabricated on 904L superaustenitic stainless steel by the electrochemical treatment in ethylene glycol electrolyte containing perchloric acid. The effects of experimental conditions, such as electrolyte temperature and applied voltage on nanoporous morphology, were studied by the way of scanning electron microscopy. The results show that lower solution temperature promotes formation of orderly nanopores. Nanoporous anodic films cannot be formed, and pitting will appear on the stainless steel when temperature is above 40uC. The sizes of pores gradually increase with increasing applied voltage when the applied voltage is lower than 30 V. Porous morphology will change from roughly circular to polygonal, and the size will change from uniform to uneven when the applied voltage is higher than 30 V. It is difficult to form orderly nanoporous anodic films when the applied voltage is too high. Difference of element content in stainless steel is also an important factor for the porous morphology. When the applied voltage is 50 V, orderly pores are formed on 316 austenitic stainless steel surface. However, under the same conditions, this phenomenon does not occur on 904L superaustenitic stainless steel surface. From the analysis of X-ray photoelectron spectroscopy, the films are composed of various metal oxides.

Nanoporous Stainless Steel Materials for Body Implants—Review of Synthesizing Procedures

“…All these results were reported for samples treated for 600 s. A sample was also treated for 300 s, and un-ordered surface morphology was observed. Lu et al [ 39 ] also reported that pitting appeared on this type of stainless steel when the electrolyte temperature was about 40 °C.…”

“…Lu et al [ 39 ] also performed the synthesis on stainless steel type 904L. Several different voltages were used.…”

“…The initial current density decreased significantly (by an order of magnitude) after about 30 s and stabilised at a very low value for the case of 4 °C, whereas the current density at 30 °C remained moderate at a value of about 0.07 A/cm 2 . Lu et al [ 39 ] also acquired SEM images of the samples treated for 10 min at those temperatures and found perfectly ordered nanopores at 4 °C, whereas the nanopores at 30 °C were stochastically distributed and somehow larger.…”

“…In addition, Lu et al [ 39 ] performed anodisation of stainless steel 904L at different voltages, but at the same treatment time of 600 s and electrolyte temperature of 4 °C. They found an enormous dependence of the pore diameter on voltage.…”

Fabrication of Thick Anodic Films on 304-Type Stainless Steel for Binder-Free Supercapacitors

“…Among these films, highly porous oxide films formed on stainless steel is more promising candidate to act as nanoporous active materials, because they can provide high pseudo capacitance due to more reaction sites of large surface area nanostructured Fe2O3, and acceptable electrical conductivity of Fe3O4. However, the limited thickness of the anodic films on stainless steel substrates via galvanostatic anodization is generally restricting the mass of active materials [9][10][11][12][13]. Furthermore, the effects of film thickness on supercapacitance behavior of anodic oxide films have not been well studied because it is difficult for electrolyte ions to penetrate into thick nanoporous films.…”