The Hydrogen Blistering Formed on the Surface of A333Gr6 Pipeline Steel Exposed to Wet H2S Solution

Abstract

After Hydrogen-induced cracking (HIC) test, many hydrogen blisters appeared on the surface of A333Gr6 pipeline steel. The amount of hydrogen blistering depends on the sample location. The amount and area rate of the hydrogen blistering on the surface of A333Gr6 sample near the internal wall are more than those of the sample near the external wall. After the upper part of the hydrogen blisters were torn off, the fracture surfaces of the upper and lower parts of the blister were analyzed by scanning electronic microscopy (SEM) and energy dispersive spectroscopy (EDS). The cell segregation inclusion of alloying elements which contain Ca and Al sulfides and oxides were observed in most of the nucleation sites of hydrogen blisters. The result shows that the dislocations and the increasing vacancy concentration are the main reasons to form hydrogen cavities in the nucleation sites. The hydrogen pressure which exceeds the strength of the materials will cause the formation of hydrogen blister.