The addition of silicon to steels has been found to strongly increase the material’s resistance to corrosion in liquid lead–bismuth eutectic environment; however the mechanical properties of ferritic–martensitic elevated silicon steels are also strongly affected by the liquid metal environment. This paper discusses the assessment of the mechanical properties of silicon enriched high Cr steels T91, T91-Si, EP823, S2439 and S2440 when in contact with LBE. The stability and strength of the material’s oxide layer was examined by nano-indentation and the oxide layer of EP823 was found to be harder and stiffer than that of T91. Furthermore, the nano-indents caused cracking of the oxide layer at the matrix–oxide interface in EP823 while no cracks were observed due to nano-indentation in the T91 oxide layer. These findings are then related to the respective material’s susceptibility to liquid metal embrittlement.