Effects of Triazine-Based H2s Scavenger Byproducts on The Film Composition and Cracking of Carbon Steel Utilizing in-situ Surface Enhanced Raman Spectroscopy

The common practice used to reduce the concentration of hydrogen sulfide (H2S) in the hydrocarbon production fluids is to inject an H2S scavenger into the gas transmission line. However, failures in the form of stress corrosion cracking (SCC) of steel pipes have been reported when using certain triazine based scavengers. One mole of triazine generally reacts with two moles of H2S from the gas stream and liberates two moles of amine, thiadiazine, and dithiazine. The MEA byproducts that form during the scavenging process have been hypothesized to cause SCC.A vast amount of information available in scientific journals and technical papers have served as a database for documenting corrosion problems associated to MEA-CO2/H2S sweetening reactions. However, the corrosive effects of MEA-triazine byproducts are still unknown. Based on these findings, it is suggested that SCC is governed by corrosion processes and specifically by a possible transition from a passive to an active surface. This transition is a complicated function of sour gas concentration and amine adsorption. In this work, we seek to explore the role of MEA-triazine byproducts on SCC of carbon steel. In-situ Raman spectroscopy was used to identify the chemical species present in the test solution prior to and following the scavenging process. Surface-Enhanced Raman spectroscopy was utilized to measure specific adsorption of amine byproducts on the steel, as well as, changes in the surface film composition based on previous electrochemical studies. Finally, slow strain rate testing was performed to evaluate SCC susceptibility.