The effect of trace rare earth treatment on the pitting corrosion resistance of austenitic stainless steel in a 3.5 wt.％NaCl solution was studied using electrochemical impedance spectroscopy and potentiodynamic polarization methods.The morphology and composition of inclusions were characterized using techniques such as scanning electron microscopy(SEM)and energy dispersive X-ray spectroscopy(EDS).The inclusions in stainless steel without rare earth addition are mainly composite inclusions of(Al,Mg,Si)-Ox;after adding 0.003 5％trace rare earth elements,the inclusions were modified to composite inclusions containing rare earth elements.The electrochemical test results show that the pitting potential of rare earth micro treated steel increases,which helps to improve the material's pitting resistance.The Mott-Schottky measurement results also indicate that the density of the passive film on austenitic stainless steel is enhanced,the carrier concentration decreases,the passive film appears as an n-type semiconductor,and the corrosion resistance increases.The improvement of seawater pitting resistance of austenitic stainless steel treated with trace rare earth elements is mainly attributed to the formation of rare earth composite sulfur oxides,which reduces the corrosion activity of inclusions.
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