Construction And Performance Of The Superhydrophobic/Slippery Surface On Stainless Steel

Super-hydrophobic and super-slippery surface have broad application prospects in many areas due to their special wettability,such as self-cleaning,drag reduction,anti-corrosion,waterproof,anti-fouling,anti-icing,etc.However,the micro-nano structures of the super-hydrophobic / super-slippery surfaces obtained in current research are relatively fragile,and other performances,such as abrasion resistance,high temperature resistance and impact resistance,are far from the requirements of industrial applications.Austenitic stainless steel,as an engineering material with excellent corrosion resistance and formability,is widely used in industrial and agricultural fields,and also in daily life.The construction of super-hydrophobic/ super-slippery surfaces on stainless steel may endow it with more unique properties and broaden its application range.Based on the above background,this study planned to explore a more economical and practical process of super-hydrophobic /super-slippery surfaces on stainless steel,and the obtained surface can meet the comprehensive environment,requirements on its properties,such as corrosion resistance,wear resistance,super-hydrophobicity and super-slippery character,etc.The results of this study can provide strategy for the construction of durable micro-nano structures on stainless steel and the selection of low surface energy modifiers,and provide technical support for the industrial application of the super-hydrophobic and super-slippery surfaces on stainless steel.This study used a simple and easy chemical etching method to prepare a deep micro-scale structure on the surface of austenitic stainless steel,and then integrated nano-scale structure with different morphologies prepared by different processes.After modified with fluorine-free myristic acid,super-hydrophobic surfaces were obtained.Afterwards,silicone oil lubricant was infused into the micro-nano structure to construct a super-slippery surface.The structure and performance of the super-hydrophobic and super-slippery surfaces(super-hydrophobicity,super-slippery character,corrosion resistance,wear resistance,resistance to different liquids and high temperature resistance,etc.)were comprehensively analyzed and evaluated.Firstly,a deep micron-scale structure on the stainless steel surface was constructed by hydrofluoric acid etching.The effect of etching temperature and time on surface morphology was studied.The surface etched in 40 wt.% HF acid at 70°C for 60 minutes presents an uniform micron structure with a depth of 45 ?m,which plays a protection role for the nano-scale structure during wear.At the same time,the four processes of nanostructure preparation(chemical etching with hydrochloric acid and ammonium persulfate,hydrothermal treatment,high temperature oxidation)were optimized,and four different nanostructures(pit-like,sheeted,layered,granular)with uniform morphology and moderate size were obtained.Then,four different morphologies of micro-nano composite structures(micro plus pit-like,sheeted,layered,and granular nano-structures)were successfully constructed by combining the optimized micro-scale structure with four optimized nano-scale structure.After modified with myristic acid,the four surfaces have reached a superhydrophobic state,presenting excellent super-hydrophobic and self-cleaning performance,with contact angles of166°,164°,165°,159°,respectively,and rolling angles of 5°,2°,2°,2°,respectively.Meanwhile,the four micro-nano composite structures can maintain super-hydrophobic properties after moving 100 cm under a pressure of 3.2 k Pa in sandpaper abrasion test,and the three superhydrophobic samples with micro plus sheeted,layered and granular nanostructures can withstand water impact at a high velocity of 13.24 m/s for 10 min or more.It is found that the corrosion potential of each superhydrophobic sample(SHS)is improved compared with the original sample,and their passive current densities decrease significantly.These results indicate that the four superhydrophobic surfaces prepared in this study have good wear resistance,good impact resistance and excellent corrosion resistance.In order to further improve the stability and lyophobicity of the super-hydrophobic surface,the micro plus layered-nano composite structure was selected as the base for the preparation of the super-slippery surface(SLIPS),due to its characteristics of more pores,layered structure,thicker nanostructure layer,which are more conducive to the storage of lubricating fluid.The differences in the wettability(contact angle,rolling angle),sliding speed,stability(water flow stability,thermal stability)of the silicone oil infused surfaces with different viscosities(50-500 m Pa·s)and the self-healing performance,corrosion resistance and lyophobic performance were investigated of the SLIPS infused by the best viscosity of silicone oil.The results show that there is no significant difference in the wettability and sliding speed of the surfaces infused by silicone oil with different viscosities,while the water flow stability of the surface infused by silicone oil with a viscosity of 500 m Pa·s is the best.Therefore,500 m Pa·s silicone oil is recommended as silicone oil selection for SLIPS preparation.After maintaining at 100°C for 7 days or being scratched by the blade,the SLIPS infused by 500 m Pa·s silicone oil maintains super-slippery performance,indicating that it has good thermal stability and self-healing properties.Compared with the original sample,its corrosion potential is significantly improved,and its passivation current density is more significantly reduced by 5 orders of magnitude,indicating that the corrosion resistance of the SLIPS is significantly improved.In the evaluation of the lyophobic performance of the superhydrophobic and super-slippery samples in the commonly used oils and liquids,the lyophobic range of the superhydrophobic samples modified with myristic acid and fluorine-free silane is smaller than the samples modified with the fluorine-containing silane.Meanwhile,the super-slippery surface infused by silicone oil presents a much wider range of liquid repellency and high thermal stability,that is,it exhibits better liquid repellency than the super-hydrophobic surface in various oils or liquids.