Effect of H2S/CO2 Corrosion Scale on Hydrogen Permeation

Hydrogen induced cracking (HIC) of pipeline steel caused by H₂S in sour gas field is one of the most important failure forms. Although NACE TM0284 can be used to assess HIC, there is a lack of sufficient knowledge of HIC risk under especially sour conditions such as H₂S partial pressure higher than 1MPa. At these conditions, since the electrochemical corrosion under H₂S/CO₂ coexistence conditions is very serious, the formation of corrosion product scale on the steel surface might significantly affect on the hydrogen permeation and the occurrence of HIC. In order to reveal the mechanisms of this kind of phenomena under high H₂S partial pressure, high temperature and pressure corrosion simulation experiments and D-S cell tests are used to analyze the effects of different corrosion product scales on hydrogen permeation under various H₂S containing environment condition. The results show that, the scale dominated by Mackinawite promoted the hydrogen permeation behavior, otherwise the scale dominated by Pyrrhotite strongly inhibit hydrogen permeation behavior.