Study On UV/O₃ Assisted Formation Of Protective Film On Stainless Steel Surface And Properties

Stainless steel（SS）is an important metal material with a wide range of applications,but it is prone to failure in some special working environments,so it is critical to study its surface protective film.At present,self-assembled（SA）film has developed rapidly as a protective film on metal surfaces.Compared with inorganic coating,Langmuir-Blodgett（L-B）film,and other common protective film on metal surfaces,self-assembled film technology is endowed with convenient operation and environmental friendly.At the same time,metal surfaces of any shape are suitable for self-assembly film protection technology.Before preparing self-assembled film,the metal surface is often required to be activated for forming a higher performance protective film.Up to now,the commonly used activation method is strong oxidizing solution treatment,but this treatment method will cause damage（such as corrosion）to the substrate surface.Therefore,it is obliged to seek an activation treatment method that hardly damages the stainless steel surface.In this thesis,ultraviolet/ozone（UV/O₃）pretreatment was used to activate stainless steel,and two kinds of protective film with excellent properties was successfully prepared on its surface.In addition,the method of forming organosilane molecular film on the surface of textured stainless steel assisted by UV/O₃ pretreatment was explored.In this thesis,contact angle measuring instrument,electrochemical workstation,atomic force microscope,friction and wear testing machine,X-ray photoelectron spectrometer,and other equipment were utilized to study the formation and performance of protective film on stainless steel surface.Firstly,the effect of UV/O₃ pretreatment time on the wettability and roughness of stainless steel surface was analyzed.Then,the methods of UV/O₃ pretreatment assisted formation of PFDS protective film and PDMS protective film on the stainless steel surface were studied.The film-forming mechanism was discussed and the related properties were characterized.Further experiments showed that UV/O₃ pretreatment could effectively improve the film formation effect on the stainless steel surface.Finally,the method of forming PFDS protective film on textured stainless steel assisted by UV/O₃ pretreatment was investigated,and the related properties were characterized.The details of the researches in this thesis are as follows:（1）Study on the preparation and performances of organosilane molecular protective film on stainless steel assisted by UV/O₃ pretreatment.The wettability and roughness of the stainless steel surface will change after UV/O3pretreatment.When the UV/O₃ pretreatment time is 20 min,the stainless steel surface has the advantages of the best hydrophilicity and the lowest roughness.The organosilane molecular film was prepared on the surface of stainless steel after UV/O₃ pretreatment for 20min.and the effect of self-assembly conditions（self-assembly time,concentration of self-assembly solution,curing temperature）on the film formation was investigated.The results showed that after UV/O₃ pretreatment for 20 min,the surface of stainless steel was immersed in PFDS solution with the concentration of V_PFDS:V_ethanol=1:50 for 6 h,taken out and cured at 120^oC for 1 h,the organosilane molecular protective film with excellent corrosion resistance could be successfully obtained.In the end,the film-forming mechanism was analyzed and the protective properties were characterized.（2）Study on the preparation and performances of polysiloxane polymer protective film on stainless steel surface assisted by UV/O₃ pretreatment.A polysiloxane polymer protective film was prepared on the stainless steel surface after UV/O₃ pretreatment for 20 min.The effects of self-assembly conditions（self-assembly time,concentration of self-assembly solution）on the film formation was investigated by contact angle measuring instrument and electrochemical workstation.The results showed that after UV/O₃ pretreatment for 20 min,the surface of stainless steel was immersed in PDMS solution with the concentration of 5 mg/m L for 0.5 h,taken out and cured at 120^oC for 1 h,the PDMS film with excellent performance could be successfully achieved,and the film-forming mechanism was analyzed.The original stainless steel,film-formed stainless steel without UV/O₃ pretreatment and film-formed stainless steel with UV/O₃ pretreatment were characterized by electrochemical test,corrosion test,and friction and wear test,respectively.The results show that UV/O₃ pretreated film-forming stainless steel exhibits better corrosion resistance and wear resistance compared than the other two samples,indicating that UV/O₃ pretreatment can effectively improve the film formation effect on the stainless steel surface.（3）The UV/O₃ assisted formation of perfluorosilane organosilane molecular film on the textured stainless steel surface was explored.Using high-precision,large-area micro-nano scratch processing equipment to process stainless steel,different textures were processed on its surface,and the influence of texture processing parameters（scratch interval and scratch load）on the friction and wear resistance of stainless steel surface was studied.The results show that when the scratch interval is 5μm and the scratch load is 40 m N,the processed texture has the greatest improvement on the friction reduction and wear resistance of the stainless steel surface.Organosilane molecular film was prepared on the textured stainless steel surface with the aid of UV/O₃.The results of contact angle test and dynamic hydrophobic performance test reveal that the the surface of textured stainless steel after film-formed has good hydrophobic performance and great dynamic hydrophobicity,which effectively improves the waterproof and antifouling ability of the surface.The results of electrochemical test and friction and wear experiment show that the corrosion resistance and wear resistance of the surface of textured stainless steel after film-formed are improved.To sum up,UV/O₃ activation treatment is a kind of stainless steel surface activation pretreatment method that hardly damages the substrate.In this thesis,the effect of UV/O₃pretreatment time on properties of stainless steel surface was studied,and PFDS film and PDMS film with great protective properties were successfully prepared on the stainless steel surface assisted by UV/O₃.It is verified that UV/O₃ activation treatment can effectively improve the film-forming effect on the stainless steel surface.Finally,the formation of organosilane molecular protective film with excellent protective performance on the textured stainless steel surface assisted by UV/O₃ was explored.This study confirmes the nondestructive pretreatment method of stainless steel surface,further enriches the preparation method of high-performance protective film on stainless steel,which provides an important basis for the preparation of high-performance protective film on other substrates.