The electrical AC impedance response of oxide scales on 9Cr–1Mo steel immersed in molten lead–bismuth eutectic alloy at 200 °C

• Oxide scales on 9Cr–1Mo in LBE have similar impedance to HT-9 and 316L scales.
• Impedance magnitude does not necessarily correlate with oxide thickness.
• Significant impedance indicates good coverage of a protective oxide scale.

Coupons of 9Cr–1Mo steel were pre-oxidized in hot air and then partially immersed in molten lead–bismuth-eutectic alloy at 200 °C for various durations. The oxide resistance and capacitance were measured using an AC electrical method. Impedance was found not to correlate with oxide thickness. In connection with other studies on HT-9 and 316L steels, it can be tentatively suggested that oxides on ferritic–martensitic steels may be more conductive than oxides on austenitic steels.