A Customized Milli-fluidic Flow Cell Technique for Simultaneous Assessment of Corrosion and Silica Scaling

Abstract Amorphous silica (SiO2) precipitation is amongst the most common scaling issues encountered in high-enthalpy geothermal systems. The presence of dissolved gases such as carbon dioxide (CO2) and hydrogen sulfide (H2S) within geothermal fluids means that silica scaling is often accompanied by infrastructure corrosion. Despite the requirement for improved mitigation strategies, the relationship and inter-dependencies between scaling and corrosion remains poorly understood. One reason for this is the challenge in replicating and monitoring both corrosion and silica scaling processes simultaneously at laboratory scale. This paper presents the development and implementation of a novel flow cell technique designed to quantify the corrosion behavior of carbon steel during controlled and sustained silica precipitation. The system offers several advantages over existing laboratory methods: (i) it operates as a once-through setup, maintaining consistent water chemistry and enabling continuous precipitation; (ii) it induces silica precipitation via temperature reduction rather than pH adjustment; (iii) it allows for in-line chemical injection at various stages of the geothermal fluid cycle; and (iv) it supports continuous, real-time monitoring of corrosion rates using electrochemical methods. In this paper, details pertaining to the silica depolymerization system, flow cell design and its electrochemical integration are presented. The fluid flow characteristics of the electrochemical cell are modeled and experimentally assessed in terms of fluid-fluid displacement. The performance of the flow cell and associated techniques are evaluated for X65 carbon steel exposed to a CO2-containing brine with 640 ppm and 960 ppm dissolved monomeric SiO2 at pH 6 and 80 °C. Finally, the paper concludes with proposed next steps and outlines opportunities to realize the potential of the developed system.