Mn对2205双相不锈钢耐点蚀性能的影响

研究锰元素对2205双相不锈钢耐点蚀性能的影响, 锰质量分数的变化范围为0. 93%~1. 26%.分别采用化学腐蚀法、动电位极化法研究双相不锈钢2205的耐腐蚀性能, 采用夹杂物自动分析技术研究锰对钢中夹杂物种类及数量的影响, 通过扫描电镜、能谱及夹杂物原位分析法观察化学腐蚀及电化学腐蚀前后钢中夹杂物及其周围钢基体的变化情况.采用电感耦合等离子体发光光谱测定腐蚀产物的成分.研究结果表明, 不同类型的夹杂物对耐腐蚀性能的影响不同, (Mn、Si) 氧化物以及(Mn、Si、Cr) 氧硫化物在腐蚀液中更易溶解进而促进腐蚀, 而(Cr、Mn、Al) 氧化物却很稳定.锰的加入会促进钢中(Cr、Mn、Al) 夹杂的析出, 此类夹杂物不仅自身很容易被含Cl离子的溶液腐蚀, 而且作为点蚀的起始点, 促进了点蚀坑的形成, 加快了基体腐蚀, 最终导致不锈钢耐点蚀性能的下降. 

Effect of manganese addition on resistance to pitting corrosion of duplex stainless steel S32205

Duplex stainless steel (DSS) has been applied to marine industries, chemical plants, and nuclear facilities because of its high mechanical strength, good weldability, good resistance to pitting corrosion in various aggressive environments, and relatively low cost than similar-performance materials. However, with the decline of iron and steel industries, the competition among stainless steel products is becoming fierce. To reduce the costs of stainless steel, enterprises have attempted to replace high-priced alloy elements with low-priced alloy elements. Thus, the project of substituting manganese for nickel has attracted considerable attention. In this study, effect of manganese addition in the range of 0. 93%-1. 26% on the resistance to pitting corrosion of duplex stainless steel in chloride medium was investigated. Chemical corrosion and potentiodynamic anodic polarization tests were conducted to assess the resistance to pitting corrosion. Categories and number of inclusions were analyzed using inclusion automatic analysis technology. Changes of inclusions before or after chemical and electrochemical corrosion were observed using in situ observation, scanning electron microscope and energy dispersive spectrometer analysis. Inductively coupled plasma test was conducted to analyze compositions of corrosion products. The results indicate that different inclusions have different effects on pitting corrosion. Types of (Mn, Si) oxides and complex inclusions of (Mn, Si, and Cr) oxysulfides are dissolved, which accelerates the corrosion process. However, the types of (Cr, Mn, and Al) oxides are stable in similar environment. The addition of manganese leads to the deterioration of the resistance of dplex stainless steel to pitting corrosion because manganese accelerates the formation of (Mn, Si) oxides that act as initial locations of pitting corrosion in chlorine ion corrosion environment. Dissolved inclusions help to expose fresh matrix to etchant solution, accelerating the corrosion ofthe matrix. Thus, the corrosion of the duplex stainless steel matrix is more serious than that of the inclusions.