Researches On Anticorrosive Mechanism And Application Of Oil-soluble TiO₂Nanoparticles

With the rapid development of nano and surface modification technology, manyscholars expected a breakthrough in the application of nanoparticles as new lubricantadditives,and significant achievement in the qualitative leap of lubricant performance.Because of small size effect and surface effect, there are a large number of hydroxylgroups on nano-TiO2surface,so the nanoparticles were vulnerable to agglomeration.Itwas difficult for nanoparticles to dispersing in oil. In order to effectively controllingsize of nano-TiO2particles,and improveing the dispersion stability in the lubricatingoil, organic surface modification was employed.In this paper, the process of preparation and surface modification of nano-TiO2particles using oleic acid and DTMS as modifier was studied. Oil-soluble TiO2nanoparticles which had excellent suspension stability and dispersion stability inlubricating oil were prepared. Influence of TiO2on anticorrosive properties oflubricating oil and anticorrosive mechanism was researched. The feasibility of TiO2asanticorrosive additives was explored, and the obtained TiO2was successfully appliedin new ordnance oil.TiO2nanoparticles modified by oleic acid were prepared by the in-situ synthesismethod. The particles were relatively uniform with average particle size of44nm. Theinteraction between carboxyl and nanoparticles was not physical adsorption, but viathe formation of bidentate chelate. The modified layer on the surface of TiO2nanoparticles prohibited effectively the agglomeration of particles while improved theanticorrosion properties of lubricating oil. The highest anticorrosive properties of TiO2nanoparticles in lubricating oil were found under the conditions of modifyingagent:TiO2=3:4(mol) by adding5%(mass)TiO2.TiO2nanoparticles modified by DTMS were prepared by the liquid phasedeposition method. The highest lipophilic degree and suspension stability of TiO2nanoparticles in lubricating oil were showed with the modifying agent:TiO2=2:1(mol)and modified time of12h at40℃. The particle size distribution in lubricating oil wasalmost gaussian distribution with the average particle diameter of60nm.According tothe results of FT-IR and TEM, the modified layer on the surface of TiO2nanoparticlescontrolled effectively the excessive growth of particles, prevent the agglomeration ofparticles, and enhanced the suspension stability and dispersion stability ofnanoparticles in lubricating oil. According to the results of electrochemical experiment and humidity cabinet test, the anticorrosive properties of oil film wasimproved evidently by adding5%(mass)TiO2to lubricating oil.Anticorrosive Mechanism of oil-soluble TiO2nanoparticles in0.5%neutral NaClsolutions were studied by electrochemical impedance spectroscopy.The wholecorrosion processes could be separated into several periods:(l) induction period ofpitting corrosion;(2) development period of pitting corrosion;(3) general corrosionregion;(4) accelerated corrosion region. The anticorrosive ability of oil-soluble TiO2was mainly reflected in increasing induction period of pitting corrosion anddevelopment period of pitting corrosion.On the basis of the above research and special demand of the ordnance oil, theapplication research of oil-soluble TiO2nanoparticles modified by DTMS werecarried out. Thereafter the working fluid for oil-gas suspension was preparedsuccessfully using TiO2as anticorrosive additives. The studies indicated that TiO2nanoparticles had compatibility to other oil additives. No negative effect was found onhigh and low temperature performance of the working fluid. Because of the TiO2nanoparticles, the anticorrosive properties and lubricating performance of the workingfluid were significantly increased.