A new experimental high temperature electrochemical system was designed for
measuring electrochemical corrosion rates in high temperture dilute electrolyte solutions. The
system was tested at temperatures up to 360oC and pressures up to 26 MPa. The ion
concentrations in the aqueous boiler solutions are typically low, which makes corrosion rates
difficult to quantify using the traditional mass loss and metallography techniques. The newly
designed electrochemical system with annular-duct flow-through working-counter electrode
assembly was proved to be efficient for in-situ corrosion studies. The DC polarization and
electrochemical impedance spectroscopy (EIS) methods were found most applicable
techniques to measure the corrosion current in the high temperature/low density subcritical
environments.