Study of the composition and properties of iron sulfide during hydrogen sulfide corrosion in the vapor phase

Moscow obl., 142717, Russia; *e-mail: R_Vagapov@vniigaz.gazprom.ru The impact of hydrogen sulfide contained in hydrocarbons extracted at oil and gas facilities on steel equipment and pipelines is dangerous not only due to corrosion damage, but also due to hydrogen penetration into carbon and low-alloy steels. However, such a negative impact on the durability and properties of structural materials has previously been studied mainly for liquid conditions typical of oil fields. The paper presents the results of a study of internal corrosion processes at gas fields. The patterns and features of the composition and properties of deposits formed in gas pipelines during the interaction of H 2 S-containing gas with steel were analyzed. Using the X-ray diffraction method, it was determined that the main corrosion product is iron sulfides (tetragonal and cubic), formed in the gaseous and liquid phases. The forms of hydrogen sulfide corrosion product crystals formed on the steel surface were studied using scanning electron microscopy. The effect of differences in their phase composition and crystalline forms on general corrosion losses and hydrogenation of steels was revealed. In addition, the lack of continuity in the iron sulfide film can lead to the formation of local corrosion defects on steel structures. The results obtained can be used to assess the degree of danger of hydrogen sulfide corrosion on steel equipment in gas fields and pipelines, as well as to select anti-corrosion protection agents (e. g., corrosion inhibitors).