Electrochemical Properties of Carbon Steel Corrosion in Boiler Water at Elevated Temperatures

Water treatment programs are a key factor in steam cycle power station safety. They are one of the first lines of defense against a wide range of corrosion-induced boiler system failures. To further facilitate the development of effective boiler water treatment programs, it is important to fully understand the nuances of the underlying corrosion process. Though waterside corrosion of tubing in steam cycle power stations is an old problem, many aspects of the underlying processes are remain poorly defined at elevated temperatures and pressures. These gaps in our current understanding complicate the development and validation of new corrosion mitigation treatments. Here we demonstrate how a series of electrochemical techniques can be used to fill in some of these gaps when coupled with electrochemical theory and a high temperature & pressure condensed phase corrosion sensor. In this study, we investigated the kinetics of carbon steel corrosion in simulated boiler waters at elevated temperatures and pressures. Electrochemical properties (Tafel slopes and corrosion currents) of the corrosion processes were obtained and compared between techniques such as linear polarization resistance, electrochemical impedance spectroscopy and potentiodynamic scans. These comparisons demonstrated the power of using multiple techniques to better understand the behavior of elevated temperature corrosion. Furthermore they can serve as the benchmarks needed to verify the effectiveness of new water treatment programs.