Effective corrosion-inhibition solution for prolonging service lives of pipe materials for seawater-for-toilet-flushing (SWTF) systems: Plant-scale and lab-scale studies

Abstract

SWTF is an effective water-resource solution for coastal mega-cities but the ageing of pipeline materials by long-term seawater corrosion can be a costly problem to resolve. In this study, the corrosion inhibition effects and inhibition mechanism of 25 mg/L Ca(OH)2 on ferrous materials under seawater environment were examined by weight-loss measurement and various electrochemical methods. The results indicated that addition of 25 mg/L Ca(OH)2 serves as a mixed-type inhibitor to decrease the corrosion rate of ferrous materials by around 30 % during 14 days of immersion in simulated seawater environment and around 66 % during 180 days of immersion in fresh seawater environment. Microstructural investigation indicated that the addition of 25 mg/L Ca(OH)2 promotes the amount of aragonite (CaCO3) precipitates on the sample surface that can inhibit corrosion by decreasing the diffusion of dissolved oxygen and ions to the surface of steel. These results indicate that Ca(OH)2 is a promising corrosion inhibitor for ferrous pipe materials for carrying seawater in SWTF systems.