Effect Of Passivation Potential On The Structure And Property Of Passivation Film For Cu-bearing 316L Stainless Steel

Copper bearing stainless steel is a new type of structural/functional material,and the release of Cu ions is main antibacterial mechanism.Passivation film is the key factor to regulate the antibacterial property of the stainless steel when it is contacted with the medium environment.In this work,316L stainless steel was used as control group,many electrochemical methods,such as the Potentiodynamic polarization,the Potentiostatic polarization,the Mott-Schottky analysis,the Electrochemical Impedance Spectroscopy,the X-ray photoelectron spectroscopy(XPS)analysis technique,were employed to investigate the corrosion behavior of 316L-Cu stainless steel and 316L stainless steel for comparison in 0.5 mol/L H₂SO₄solution.Hereinto,the electronic properties,structure and composition of passive film for the passivated316L-Cu stainless steel were analyzed by Mott-Schottky and XPS method.In addition,passivated 316L-Cu stainless steel was placed in simulated physiological environment(0.9 wt.%Na Cl solution)for electrochemical immersion test.The Linear Polarization Resistance and Electrochemical Impedance Spectroscopy of different immersion days were analyzed to obtain the influence of passivation potential on the performance of316L-Cu stainless steel passive films.The following conclusions can be obtained:The corrosion resistance of 316L stainless steel in 0.5 mol/L H₂SO₄solution can be slightly improved by adding Cu.The copper rich phase precipitated from the matrix of 316L stainless steel containing copper will hinder the surface reaction of stainless steel in the active zone during anodic dissolution In H₂SO₄solution,compared with 316L stainless steel,the passivation range of 316L-Cu stainless steel did not change significantly,and the addition of Cu did not change the passivation mechanism of 316L-Cu stainless steel.Moreover,the addition of Cu does not change the microstructure of 316L stainless steel.The passive films of 316L stainless steel and 316L-Cu stainless steel under different passivation potentials show N-type and P-type semiconductivity and have a double-layer structure.For 316L stainless steel passive film,the increase of passivation potential reduces the point defect concentration of passive film.With the increase of passivation potential,the number of carriers in the space charge layer of the passive film of 316L stainless steel decreases,which also means that the conductivity of the space charge layer is weakened,which means that the corrosion resistance of the passive film is enhanced for the passive film with shielding effect.However,for 316L-Cu stainless steel passive film,the increase of passivation potential increases the concentration of point defects in the passive film,which means that the corrosion resistance of the passive film is weakened for the passive film with shielding effect.With the increase of passivation potential,the Cr/Fe ratio of 316L stainless steel passive film and 316L-Cu stainless steel passive film increases,and the increase of Cr/Fe ratio improves the corrosion resistance.However,due to the dissolution of Cu²⁺from the passive film of 316L-Cu stainless steel,the concentration of point defects in the passive film increases,which makes the corrosion resistance and stability of the passive film worse.The results of electrochemical immersion test show that the stability of passive film of 316L stainless steel increases with the increase of passivation potential,and the stability of passive film of 316L-Cu stainless steel decreases with the increase of passivation potential.The passive film of 316L-Cu stainless steel with 0.2 V_SCEas passivation potential still has strong corrosion resistance.Proper passivation treatment can protect the passive film.