ABSTRACT

Hydrogen sulfide (H$) has long been associated with the cause of corrosion damage and sulfide stress cracking (SSC) in high strength steels and high hardness weldments used in oil and gas production, petroleum refining, and petrochemical/chemical processing. Other applications where sulfide species have produced environmental cracking include heavy water production, electric power, marine applications and many others where sulfate reducing bacteria can flourish and oftentimes produce substantial amounts of HZS. H$S has also been associated with internal blistering, hydrogen induced cracking (HIC) and stress oriented hydrogen induced cracking (SOHIC) of carbon steels used in refinery vessels in wet H2S service and pipelines containing sour (HzS-containing) fluids. In recent years, new stainless alloys have been implemented in lieu of conventional steels in many applications where H# corrosion is particularly severe. These materials have been used along with chemical inhibitors to mitigate corrosion. These alloys, however, may in some cases also be susceptible to SSC, localized corrosion and anodic stress corrosion cracking (SCC) in sour environments. In this review, the behavior of carbon and low-alloy steels, stainless steels, and nickel alloys in sour environments is discussed. Emphasis is placed on the identification of the various types of HzS-related corrosion and environmental cracking that can occur, the origin and mechanisms, and the methods of control.

INTRODUCTION

For over five decades there has been a continual need to develop new materials technology for use in industrial applications involving exposure to H$S. Much of this effort has centered around the need for higher strength and more corrosion and/or embrittlement resistant materials that can withstand high temperature, high pressure, and increasing aggressive service environments. More recent research has been directed at identifying materials that can withstand service conditions where pressures and temperatures are in excess of 135 h4Pa and 200 C, in the presence of significant quantities of corrosive gases such as H$S and CO* and aggressive species such as chlorides and sult%r compoundst?l Of even greater importance is the need for more economic stainless steels with high strength and corrosion resistance to handle service applications involving exposure to high COr partial pressures in combination with low to moderate levels of HzS (1100 kPa). ~1

Additionally, downstream petroleum refining and petrochemical environments are subject to higher levels of corrosivity as a result of processing a greater variety of impure hydrocarbon feedstocks. Impurities such as H#, organic sulfide compounds, and nitrogen compounds, result in high levels of HzS, cyanide and ammonia which can also produce conditions for SSC and HIC of steels used in plant pressure vessels and piping. I31

Understanding of the role of H$S in the degradation of engineering has remained paramount over the past several decades in research. In addition to being extremely toxic, HrS is responsible for corrosion and environmental embrittlement in common materials of construction. Consequently, it has been necessary to develop special materials and processing methods that minimize the effects of corrosive degradation and maximize the integrity of these systems. Furthermore, through an understanding of H$- related cracking mechanisms, it has been possible to monitor and make adjustments to process environments to minimize H2S corrosion and embrittleme

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