Changes in the phase composition of an oxide film on EP-823 steel in contact with stagnant lead melt

We study the structure and composition of an oxide film formed on the surface of EP-823 steel in contact with stagnant oxygen-containing lead melt (10-5-10-6 wt.% O) at 650°C for 3500 h. It is shown that a thin oxide film ([less than or equal to]100 nm) based on chromium is formed on the steel surface. The process is especially intense at the sites of appearance of grain boundaries on the surface. The film protects the matrix against the penetration of the melt. In the course of time, iron migrates through the film and not only dissolves in the melt but also forms oxide compounds in the reaction zone. We also present an analytic description of the observed phenomenon.