Investigation of the role of electrokinetic effects in corrosion deposit formation

• The redox reactions in high temperature water involve a change in ferric speciation.
• A miniature flow cell was designed for measurement of electrokinetic effects.
• An exponential dependency between fluid velocity and polarisation is found.
• Anodic processes driven by streaming potential can enhance oxide deposition.

Electrokinetic effects associated with corrosion deposit formation in simulated high temperature primary water have been investigated. A miniature flow cell was designed for the purpose of creating regions of accelerated flow to produce areas of net anodic and cathodic activity which may be characterised by determination of electrode polarisations. Post-test XRD and GDOES examination of so polarised electrodes showed that the rate of oxide deposition and the oxide structure was strongly dependent on the electrochemical corrosion potential. This work underlines the importance of anodic processes generated by streaming potentials which can lead to enhanced oxide deposition.

Potential of Electrode 1 vs. Electrode 2 (hole 300 μm) as function of the time with flow rate of 4 l/h (v at 20 °C = 15.8 m/s) at 20 °C, 200 °C and 230 °C in hydrogenated (3 ppmw of H2) and lithiated (2 ppmw of Li+) water. The curves have been offset in the vertical axis for clarity.Figure optionsDownload as PowerPoint slide