炼厂污水臭氧处理系统中奥氏体不锈钢的腐蚀行为

Corrosion behavior of austenitic stainless steel in refinery wastewater ozone treatment system

臭氧催化氧化技术在炼厂污水处理领域的应用较为广泛,但装置在长周期运行过程中经常出现不同程度的腐蚀问题,尤其是奥氏体不锈钢的设备及管道。为了明确炼厂不锈钢设备及管道在含臭氧污水环境下的腐蚀特性,采用电化学试验和浸泡试验,以316L材质为主要研究对象,系统研究了其在含臭氧模拟污水环境中的腐蚀行为,并推测臭氧与Cl^(-)共同作用下不锈钢的腐蚀机制。结果表明:环境温度升高、pH偏离中性、臭氧浓度升高、Cl^(-)质量浓度升高、SO_(4)^(2-)质量浓度降低均会增大316L在污水环境中的点蚀敏感性,使其耐腐蚀性能下降;在焊接接头中,焊缝热影响区的点蚀敏感性相对较高;在含氯污水环境中臭氧与Cl^(-)存在协同腐蚀机制,会增大316L的点蚀敏感性和缝隙腐蚀敏感性,加速316L点蚀的发生。相比于304L和316L,317L在该环境中表现出更好的耐点蚀性能。

Ozone catalytic oxidation technology is widely applied in the field of wastewater treatment of refining and chemical industries.However,there are some corrosion problems in the ozone treatment system during the long pe⁃riod operation,especially in austenitic stainless steel equipment and pipelines.In order to investigate the corrosion characteristics of stainless steel equipment and pipeline under ozone-containing wastewater,electrochemical test and simulated immersion test were used to systematically study the corrosion behavior of 316L stainless steel in re⁃finery wastewater ozone treatment system,and the corrosion mechanism of stainless steel under the combined action of ozone and Cl^(-)was speculated.The results showed that the pitting susceptibility of 316L stainless steel was im⁃proved and corrosion resistance was reduced in the wastewater,originating from the increase of temperature and ozone concentration,the deviation of pH value from neutrality,the increase of Cl^(-)concentration and the decrease of SO_(4)^(2-)concentration.Welding materials had the highest pitting susceptibility in the heat-affected zone.The synergis⁃tic corrosion of ozone and Cl^(-)in chlorine-containing wastewater increased the pitting susceptibility and crevice cor⁃rosion susceptibility of 316L,and accelerated the occurrence of metal pitting.Compared with 304L and 316L,317L showed better pitting corrosion resistance.