The effect of temperature and oxygen content on the flowing liquid metal corrosion of structural steels in the Pb-Bi eutectic

摘要

We performed corrosion tests of 1000h each on approximately 20 types of structural steels (austenitic, ferritic and martensitic) in convection loops with flowing Pb-Bi at 500, 450 and 400℃ and a temperature gradient of 100℃. These experiments were performed in liquid Pb-Bi with different oxygen concentrations (from approximately 1 x 10~(-6) to 2 x 10~(-5) wt.%) to ascertain at what oxygen concentration and up to what temperature the oxygen technology can create protective oxide or spinel layers to reduce or prevent corrosion. The results showed that the structural materials contemplated for building an ADS system, including 9% Cr-1% Mo (W) martensitic steels and similar steels with a higher Si content (2-3%), can be used with their surface unpassivated at up to 450℃ and suffer only minimal corrosion (up to 5 μm/year). At higher temperatures, their surface must be passivated prior to and regularly during the operation; however, no technology to perform such passivation in the presence of Pb-Bi is known that this time. In addition, we measured the impact of various alloying elements, such as Fe, Cr, Ni, Mn, Si, Al and Mo, on the corrosion of such steels and searched for potential ways to passivate their surface or create protective oxide or spinel layers during operation by varying the amount of oxygen in liquid Pb-Bi.