Effect of H2S partial pressure on corrosion behavior of SA387M Gr.11CL2(H)refining pipeline steel
In order to study the effect of H2S partial pressure on corrosion behavior of SA387M Gr.11CL2(H)refining pipeline steel,corrosion morphology,composition and phases of the corrosion products of SA387M Gr.11CL2(H)were investigated by autoclave tests,SEM,EDS,XRD and EPMA.The results indicate that corrosion thickness loss increases with the increase of H2S partial pressure(PH2S).When PH2S≤0.5 MPa,the corrosion of SA387M Gr.11CL2(H)is general corrosion.When PH2S is 1.0 MPa,the steel encounters general corrosion accompanied with local corrosion,and the stress promotes local corrosion.SA387M Gr.11CL2(H)steel possesses good resistance to sulfide stress corrosion(SSC).Chromium compound and iron sulfide compounds with protective property in the corrosion product film plays synergistic action to prevent Cl-ingression when PH2S is less than 0.5 MPa.The content of Cr compounds in the corrosion product film is low,and the generated iron sulfide compounds are not protective when PH2S is 1.0 MPa.The H2S partial pressure affects the generation of corrosion product film.The changes of the compositions and structures of chromium compound and iron sulfide compounds are the main cause for the occurrence of general corrosion and local corrosion.