Research On Preparation Processing And Properties Of Easy-cleaning Stainless Steel

A well-cleaned and hygienic kitchen environment is one of the important signs of family life quality.In the cooking process,edible oil,seasonings and soup stock will inevitably cause some pollution on the surface of the kitchen ware.If not cleaned up promptly,it will not only hinder the cleanness of kitchen ware,but also have some bad effects on people's health.For improving the quality of our daily life,compared with traditional non-metallic kitchen materials such as marble and tempered glass,stainless steel is not only corrosion-resistant,but also strong as well as tough.Therefore,its application in the kitchen has been gradually extended from tableware to kitchenware.In the present work,three different kinds of techniques were used to prepare hydrophobic surface on 304 stainless steel to satisfy the demand of kitchen ware.In addition,a variety of processing factors which influence the wetting performance,mechanical properties,thermal shock resistance,abrasion resistance,high temperature oxidation resistance along with corrosion resistance were also studied.Chemical etching and electrochemical etching were both used to obtain hydrophobic surface on stainless steel.Further investigation found that the combination of these two processes,chemical etching followed by electrochemical etching,resulted in better overall performance of the easy-cleaning surface,which was both hydrophobic and oleophobic.The parameters of the optimized process were obtained.In the stage of chemical etching,etchant concentration was 33.3%and etching time was 60 min.In the electrochemical etching stage,etchant concentration was 40%,etching time was 15 min,and current density was 35mA/cm2.Fluorination was a necessary procedure after etching.Then,the Si-based and Al-based ceramic coatings were prepared by slurry method and plasma spraying method,respectively.After fluorination,both surfaces had excellent hydrophobic and oleophobic properties.The surface of the substrate must be sandblasted before the preparation of coating by both two processes.The Si-based ceramic coating had a slurry ratio of 1:10 and it was demanded to be sintered at 900? for 30 min in vacuum environment.Besides,for plasma spraying,the substrate was required to be preheated before the preparation of Al-based ceramic coating,followed by spraying NiAl intermediate layer and Al2O3 working layer in turn at current 700A and voltage 60V.These two ceramic coatings also need to be fluorinated to ensure that surfaces were both hydrophobic and oleophobic.After etching treatment,the contact angles on the samples with water and oil were 124.8°and 95.7°,respectively.The contact angles with water and oil on the surface of Si-based ceramic coating prepared by slurry were 105.0° and 91.2°,respectively.On the surface of Al-based ceramic coating layer prepared by plasma spraying,the contact angles with water and oil were 142.1° and 90.2°,respectively.Hydrophobic and oleophobic properties of the three prepared surfaces were all perdurable.Ceramic coatings prepared by slurry and plasma spraying all had good thermal shock resistance as well as high hardness.The hardness of these two coatings were 462.03HV(slurry)and 941.73HV(plasma spraying),respectively,which was much higher than that of the original stainless steel(285.44HV).The samples after etching treatment showed lower oxidation and corrosion resistance than the original sample.However,the oxidation and corrosion resistance improved significantly by using the coating technics studied in the present work.Microscopic analysis indicated that hydrophobic surface is mainly determined by low surface energy and rough surface morphology with nano-micro composite structure.Fluorination treatment resulted in reduction of surface energy and significant improvement of surface hydrophobicity.The surface of the samples prepared by etching and plasma spraying had suitable roughness,thus it was hydrophobic and oleophobic after fluorination.The surface of the samples prepared by slurry was smooth and dense providing the resistance to adhesion of pollutants.