Chapter 5 - Hydrogen sulfide corrosion

Abstract

Hydrogen sulfide (H2S), like carbon dioxide, is a type of acid gas that is an undesirable byproduct in the oil and gas industry. H2S is a colorless, poisonous, flammable, and toxic gas with the odor of rotten eggs. H2S is produced in facilities such as natural gas processing plants, petroleum refineries, and oil and gas wells. The internal corrosion of piping, valves, and facilities owing to H2S is a well-known problem in the oil and gas industry. Internal corrosion due to H2S has several negative consequences like loss of production and revenue, damage to assets and property, injury to or loss of human life, and environmental damage and pollution. Various sour corrosion mechanisms such as hydrogen embrittlement (HE), hydrogen-induced cracking (HIC), sulfide stress cracking corrosion (SSC), stress cracking corrosion (SCC), stepwise cracking corrosion (SWC), stress-oriented hydrogen-induced cracking corrosion (SOHIC), soft zone cracking (SZC), and galvanically induced hydrogen stress cracking (GHSC) can occur. This chapter describes these corrosion mechanisms. The aim is to mitigate and prevent H2S or sour corrosion in industrial valves used in various sectors of the oil and gas industry like onshore, topside, and subsea. International Organization for Standardization (ISO) 15156/National Association of Corrosion Engineers (NACE) MR 0175 address sour service corrosion mechanisms and mitigation approaches for the upstream oil and gas industry, like facilities and valves on platforms and ships. NACE MR0103 addresses sour corrosion in downstream units like refineries and chemical plants. In general, hardness and chemistry control as well as heat treatment are essential material parameters to prevent sour corrosion. This chapter focuses on environmental limitations, hardness control, chemical composition limitations, and acceptable heat treatments of carbon steel, low-alloy steel, and corrosion-resistant alloys in sour service as per ISO 15156.