Corrosion by gas mixtures containing hydrogen sulfide at elevated temperatures is reviewed, with particular emphasis on the types of environments present in catalytic reforming and desulfurizing units of petroleum refineries. Data compiled from the published literature, from laboratory and field tests, as well as from pilot and commercial plant experience are summarized and correlated.
Within the general limits of conditions existing in these types of units, corrosion is shown to depend primarily on temperature and hydrogen sulfide partial pressure. Summary curves showing corrosion rates as functions of these two variables are presented as a guide for equipment design.
The corrosion resistance of carbon steel and chrome-moly alloys steels is approximately equal in the environments studied; the 12 Cr stainless steels offer slight improvement but their performance is erratic. The 18 Cr-8 Ni stainless steels possess excellent resistance except under the most severe service conditions. Aluminum coatings are practically immune to hydrogen sulfide attack. There is, however, insufficient experience to appraise their permanence in prolonged service.
The nature and mechanism of hydrogen sulfide corrosion is discussed with special emphasis on the properties of sulfide scales.
