Nanoscale studies of the early stages of scale formation in sour environments

Abstract

The corrosion of carbon steel in environments containing hydrogen sulfide (H2S) is a critical issue to the oil and gas industry. Although considerable research efforts have been carried out, there is not yet a complete mechanistic study for the scale formation and growth kinetics, and there exists a lack of understanding of the interrelation between the factors, which control the growth and breakdown of the scales formed in sour systems. In this work, iron sulfide scale formation on carbon steel has been studied using high-resolution scanning electron microscopy (SEM) to elucidate the nanoscale morphology of the scales formed under controlled ambient conditions with saturated H2S solutions. In addition, different electrochemical techniques open circuit potential (OCP), potentiodynamic polarization (PDP), and linear polarization resistance (LPR) measurements were used during the formation of the scales to provide further insights into the kinetics of the process. In this paper, the role of solution and reaction time on the properties of the scales formed is discussed: dynamic phase-changes are found to occur, and nanostructure formation emerges during film growth.