Assessment of Safe Operating Conditions for Corrosion-resistant Alloys in Water Injection Systems

Abstract Throughout the different phases of a water injection system's lifecycle, corrosion resistant alloys (CRAs) constituting the system may be exposed to a range of corrosive media—including natural or treated seawater, produced water, or mixtures of produced water and monoethylene glycol (MEG)—depending on the service conditions. The risk of localized corrosion in these systems is significantly influenced by the fluid composition and its physico-chemical parameters. Key factors include chloride concentration, temperature, the presence of natural biofilms (in seawater), dissolved oxygen content, pH, and residual chlorine. To define the safe operating windows for various alloys, and hence mitigate the risk of localized corrosion, an extensive test program was developed. This program involved immersion tests designed to simulate operating conditions. The primary objective was to define safe operating windows for various alloys (e.g., UNS(1) S42000, S41427, S31603, N07718, N08825, N06625, S32205, S32750) under different exposure scenarios. The test campaign specifically focused on the impact of oxygen ingress during upset conditions, with and without residual chlorine. The results provide valuable insights into material performance and help guide the selection and operation of CRAs in water injection systems. The impact of the gasket materials was also investigated.