The corrosion behavior of 16Mn steel was studied in saturated H 2 S or H 2 S/CO2 solutions containing different Cl-concentrations at 80 ℃.The microstructure and chemical composition of the corrosion products were investigated through scanning electron microscopy,energy-dispersive X-ray spectroscopy,EPMA,and X-ray diffraction.Results showed that the corrosion rate decreased with increasing Cl-concentration in saturated H 2 S or H 2 S/CO2 solution at pH 4.Conversely,the corrosion rate increased with increasing Cl-concentration in saturated H 2 S solution at pH 6.The relative H+ concentration decreased because of the increase of Cl-concentration at pH 4,and Cl-acted as a catalyst in the corrosive medium at pH 6 because the net H+ concentration decreased obviously compared with the condition at pH4.Cl-promoted the formation of Fe-deficient iron sulfide at pH 4,and the opposite effect was observed in the nearly neutral solution.The corrosion rate increased firstly with increasing Cl-concentration and then decreased in the saturated H 2 S/CO2 solution at pH 6.The corrosion products were mainly composed of two kinds of iron sulfide.Sulfide FeS 1-x was a kind of tetragonal crystal,whereas the other was the hexagonal/monoclinic iron sulfide Fe 1-x S.The corrosion film that was mainly composed of FeS 1-x did not confer a protective effect on the base metal.The atomic ratio of Fe/S was more than 1 for FeS 1-x .The appearance of sulfide FeS 1-x resembled a square block or small,needlelike,flocculent particles.The atomic ratio of Fe/S was less than 1 for Fe 1-x S,and the corrosion film mainly composed of Fe 1-x S conferred some protective property on the base metal.The sulfide FeS 1-x exhibited a long claviform morphology with a hexagonal or quadrilateral cross-sectional shape.