Electrochemical properties and hydrogen barrier properties of mixed sulphide-iron compounds

Sulphide-iron compounds are the corrosion product in hydrogen sulphide environment. When the surface of steel is covered by sulphide-iron compounds, the corrosion rate of steel becomes unpredictable. The effect on the corrosion resistance of sulphide-iron compounds layer is explored by controlling the proportion of single crystalline sulphide-iron compounds. In this study, single crystalline pyrite and pyrrhotite were synthesised through hydrothermal method. The pyrite and pyrrhotite were then mixed with ratios of 7:3, 1:1 and 3:7. The results revealed that ion selectivity was changed from cation to anion as the pyrrhotite content increased. What's more, the impedance value of the mixed sulphur iron compounds gradually decreased and the corrosion current density increased, which indicated that corrosion resistance reduced with the increasing of pyrrhotite content. As the pyrrhotite content increased, hydrogen permeation current and hydrogen content exhibited a gradual decrease, which showed an overall improvement in its hydrogen barrier properties.