High-Temperature Corrosion Characteristics of Nano-Structured Coatings in Secondary System of Nuclear Power Plants

Flow-accelerated corrosion (FAC) of carbon steel pipe systems in secondary system of nuclear power plants is one of the materials degradation issue in nuclear industry. In this study, the feasibility of nano-structured coating application based on electroless nickel plating and high-velocity oxy-fuel (HVOF) is investigated in order to reduce or mitigate the FAC of carbon steel pipes in the secondary system of nuclear power plants. While nano-structured coatings generally show higher corrosion resistance and mechanical properties compared to traditional coating techniques and additionally with low surface roughness, their corrosion characteristics in high temperature water were not evaluated fully enough.  In this study, therefore, their corrosion characteristics in ammonia and mono ethanol amine (ETA) electrolyte at room temperature as well as high temperature are firstly evaluated by potentiodynamic polarization measurement and electrochemical impedance spectroscopy. From this study, it is observed that the metal loss of coated carbon steels are drastically decreased compared to as-polished carbon steels.