An investigation into the galvanic corrrosion between mild steel and 304L stainless steel in a PWR environment

The object of this research project was to examine the effect of galvanic corrosion between mild steel and type 304L stainless steel under Pressurised Water Reactor (PWR) conditions. The study was undertaken in order to provide guidelines as to potential problems at Eskom's Koeberg Nuclear Power Station, due to the presence of mild steel (ferritic) impurities in type 304L stainless steel (austenitic) pipework. Research involved establishing the general corrosion rate of mild steel in a PWR environment and combining this with the galvanic corrosion rate of mild steel. This was carried out under various conditions, in order to simulate the actual situation at the Power Station. These conditions were primary side water at 25oC and 90oC under ambient pressures and at 300oC at approximately 6.9 MPa. The temperature of 3000C simulates operating conditions, 25oC represents complete shut-down conditions and 90oC is that temperature at which the system is held for a specified period prior to complete shut-down. Testing involved the application of potentiodynamic and standard immersion techniques to polished and precorroded inclusion specimens