Study On The Preparation Of Antibacterial 430 Stainless Steel By Anodic Oxidation

Stainless steel is widely used in different fields because of it’s good mechanical properties, corrosion resistance, machinability and the bright and clean surface. When being used in some complex conditions, the surface of stainless steel is easily contaminated by dust and smudginess and becomes a breeding ground of bacteria. However, ordinary stainless steel does not have antibacterial properties, which will limit the use of stainless steel. For some special fields, such as kitchen and bathroom products, biological medicine application, clean and sterile surface of stainless steel is demanded strongly. Consequently, it’s significant to research stainless steel with antibacterial properties.This paper studied the process parameters of preparing porous iron oxide in ethylene glycol (Eg) solution containing NH4F and water on pure iron. Base on the research, the process parameters of preparing micro-nano structure on surface of stainless steel were invested. Antibacterial stainless steel were produced by deposition Cu into the micro-nano structure of stainless steel surface using electrochemical deposition. Surface morphology, phase structure, chemical compositions of the simples were characterized using SEM, XRD, EDX, XPS. Hydrophobic performances of the samples were characterized according to the contact angle measured by a video optical contact angle measurement instrument. The research results are as follows:1. Ordered honeycomb porous iron oxide was produced in the Eg solution containing O.lmol/L NH4F and 3vol.% H2O with the potential of 50V and the temperature of 0℃ for 2 hours. The diameter of nanopores was about 100nm. The surface morphology of porous iron oxide was influenced greatly by water content and temperature of the electrolyte. Increasing the water content can promote the chemical dissolution of iron oxide film and cause roughness and disordered porous surface. Pure iron anodized at the lower temperature can reduce the formation of cracks.2. When anodized in Eg solution containing 0.15mol/L NH4F and 0.05～0.4mol/L H2O with potential of 60V and temperature of 15～20℃ for 15-30min, micropores with diameter of 3～5μm were formed in the surface of 430 stainless steel and ordered honeycomb nanopores with diameter of 100nm were formed inside the micropores. However, the micropores with nanopores could only be obtained in a few locations. When moderate sodium dodecyl benzene sulfonate was added into the electrolyte, micropores with diameter of 2～5μm were formed in a large area of stainless steel. But there was no nanopores inside the micropores.3. Antibacterial stainless steel was produced by deposition of Cu into the micro-nano structure of stainless steel surface using electrochemical deposition. During the deposition process, the current density played an important role to the morphology of the antibacterial layer. The antibacterial layer was inhomogeneous with the low current density. Contrarily, the antibacterial layer may fall off from stainless steel with the excessive current density. Escherichia coli (E.coli) and Staphylococcus aureus (SA) were used as experiment bacteria for the antibacterial test. As a result, the sterilizing rates of antibacterial stainless steel were more than 99%.4. The color of the surface of stainless steel were golden after anodizing in Eg solution containing NH4F and water and the color would transform into reddish-brown by annealing treatment. Moreover, the anodized sample owned hydrophobic property because of the micro-nano structure of the surface. The hydrophobicity property of stainless steel would not change after annealing treatment. Colorful stainless steel with hydrophobic property could be produced by this method.