Corrosion Resistance of 904L Stainless Steel in Solutions Containing Cl-and F-
904L stainless steel is widely used in many industrials such as petroleum,chemical,wastewater,pipelines and papermaking due to its excellent corrosion resistance.However,the presence of chloride ion and fluoride ion in these industrials can lead to pitting corrosion in 904L stainless steel.In this study,904L stainless steel is investigated by comparative experiments to study its microstructure and corrosion products under different concentrations of chloride ion and fluoride ion using scanning electron microscopy and X-ray diffraction.The pitting corrosion behavior of 904L stainless steel is studied under different concentrations of chloride ion and fluoride ion and temperatures using electrochemical methods to explore its corrosion resistance mechanism.The results show that the polarization resistance(Rp)of 904L stainless steel decreases from 2233 kΩ·cm2 to 1246 kΩ·cm2 with the concentration of fluoride ion increasing from 0 to 0.05 mol/L,which indicates that the increase of fluoride ion concentration enhances the susceptibility of 904L stainless steel to pitting corrosion.This is because that the F-ions can form a non-dense,semi-soluble precipitate called NiF2 with the Ni atoms in the alloy,which also contributes to the composition of the passive film.As the fluoride ion concentration further increases from 0.05 mol/L to 0.30 mol/L,Rp decreases from 1246 kΩ·cm2 to 559 kΩ·cm2,which suggests that as the fluoride ion concentration continues to rise,the pitting corrosion tendency of 904L stainless steel continue to increase,but the trend of the increase gradually slowed down.In addition,the influence of the temperature on the pitting behavior of 904L stainless steel is comparatively strong while the influence of chloride ion concentration is relatively minor.
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