Corrosion behavior of heat-treated Fe–Al coated steel in lead–bismuth eutectic under loading

A protective surface alloy coating on steel surfaces can prevent steels from the heavy LBE corrosion in the LBE cooled reactor. Especially, Fe–Al alloy coating on a steel surface is effective for corrosion resistance in LBE due to the self-healing of a thin and stable Al oxide layer on the surface of the coating layer. In order to investigate the utility of the coating layer under the stress due to the hydrodynamic and thermal stress induced in the practical system. The Fe–Al coated 316SS, which was heat-treated after the coating process, was immersed in the stagnant LBE at 650 °C for 250 h with loading to investigate the corrosion behavior of the specimen with the bending stress. The Fe–Al coating layer was not corroded because of the protection by Al oxide scale which was formed on the surface of the coating layer and the interface between the coating and the matrix during the heat treatment process. The coating layer cracked elastically. The LBE penetrated into the cracks and corroded the 316SS matrix and the pre-coating layer. The matrix exhibited the dissolution corrosion caused by the preferential dissolution of Ni and the oxidation forming the Fe oxide and Cr oxide. The coating layer is effective to reduce the surface of the matrix to be corroded by LBE, and can moderate the corrosion of the depth direction.

► Fe–Al coating layer on the steel was not corroded, but cracked by the loading.
► The LBE penetrated into the cracks and corroded the 316SS matrix and the pre-coating layer.
► The 316SS exhibited the dissolution corrosion of LBE and the formation of the Fe oxide and Cr oxide.