Corrosion Electrochemical Study Of Medical High Nitrogen Nickel-free Austenitic Stainless Steel In Simulated Body Fluid

As a kind of earliest developed and used medical metal materials,medical stainless steel was widely used for implanting and other instruments.The development of medical stainless steel keeps pace with the industrial stainless steel.At present the medical stainless steel represent by 316L and 317L austenitic stainless steel is widely applied for artificial joint,bone internal fixation,heart stent and other high-end medical equipment products.After implanting into human’s body,however,the metal ions will dissolve and result to edema,infection,gangrene and other histological reactions due to the inevitable trace corrosion or wearing.As a new type of alloy,high nitrogen nickel-free austenitic stainless steel is widely used in medical,shipbuilding and oil industrial because of its good biocompatibility,pitting corrosion resistance and mechanical properties.The corrosion behavior of various kinds of austenitic stainless steel in the human body environment is different,the effects of corrosion products on the human body is also different.So it has important theoretical significance and application value to study the corrosion behavior and corrosion resistant properties of different types of medical austenitic in simulated body fluid.The main work of this paper is as follows:1.The influence of nitrogen element on the pitting corrosion sensitivity of austenitic stainless steel The 316L austenitic stainless steel and three kinds of high nitrogen nickel-free austenitic stainless steel with different nitrogen content were used as the working electrodes,a common simulated body fluid(Hanks solution)acted as a corrosive environment.In simulated body fluid the potentiodynamic polarization and electrochemical impedance spectroscopy test were applied to study the influence of nitrogen on the electrochemical characteristics like the corrosion potential,corrosion current density,pitting corrosion potential and impedance.2.The property of austenitic stainless steel passive film and the effect of nitrogen element(1)Potentiodynamic polarization and electrochemical impedance spectroscopy test were used to study the change of the passivation film performance after immersion or polarization,and the effect of nitrogen was discussed on the austenitic alloy passivation behavior(2)Scanning electron microscope(SEM)was applied to characterize the surface morphology of samples after immersion in simulated body fluid for 24h.3.The local corrosion of austenitic stainless steel in simulated body fluid was studied(1)The feedback mode of SECM was used to study the electrochemical activity distribution of the samples after different immersion time.And then the Faraday current and peak current were analyzed to study the influence of immersion time to local corrosion of austenitic stainless steel.(2)The generation-collection mode was used to study the electrochemical activity distribution of the samples after polarization,and further the change of passive film and the effect of nitrogen were analyzed.