20#钢和球墨铸铁材质燃气管道的土壤腐蚀行为比较研究

Comparative Study on Soil Corrosion Behavior of 20# Steel and Ductile Iron for Gas Pipelines

采用正交试验设计方法,以含水量、孔隙度、pH值等9种影响因素作为试验因素进行土壤腐蚀模拟试验,对20#钢和球墨铸铁的腐蚀形貌和腐蚀产物进行比较分析,探讨其腐蚀行为和腐蚀机理。分析表明:在相同环境下球墨铸铁比20#钢更容易腐蚀,它们的土壤腐蚀环境因素重要度排序呈现较大的差异,但两者对Cl-都比较敏感,在20#钢的腐蚀产物中检出了球墨铸铁腐蚀产物中没有的磷酸铁族物质Fe2PO5。含碳量少、含有抗腐蚀元素Cr、腐蚀产物中含有抗腐蚀作用的磷酸铁族物质以及晶界少是20#钢比球墨铸铁耐腐蚀性好的主要原因。

20#steel and ductile iron are two common materials used for buried gas pipelines,the study on their corrosion behavior and mechanism in soil can provide theoretical basis for corrosion and protection of gas pipelines.In this study,the simulation test of soil corrosion was carried out using the orthogonal experimental design method with 9 factors such as water content,porosity,and pH value etc.as main factors of soil corrosivity.The corrosion morphology and corrosion products of 20#steel and ductile iron were analyzed by means of SEM and XRD.Results showed that ductile iron was more easily corroded than 20#steel in the same environment,and the ranking of the relevant main factors of soil corrosivity for ductile iron and 20#steel showed great differences,but the two materials were very sensitive to Cl-.The iron phosphate group Fe2PO5,which was not found in the corrosion product of ductile iron but was detected in the corrosion product of 20#steel.The main reason why the 20#steel has better corrosion resistance than ductile iron may be ascribed to that the small amount of Cr in the steel,the presence of iron phosphate in the corrosion product,and fewer grain boundaries of the steel.