Effects of lead on oxidation behavior of Alloy 690TT within a high temperature aqueous environment

•The films on 690TT in high-temperature water with and without lead were studied.•Lead traces participated in the oxidation and were added into the oxide films.•Lead contamination could block the dehydration of hydroxides within the films.•Lead impurities could cause the production of amorphous structures in the films.•A duplex layer model was proposed for the evolution of the lead-doped films.

The chemical compositions, phases and structures of two oxide films on Alloy 690TT following exposure for 4400 h in pure water with and without lead at 320 °C were studied by surface analysis techniques. The analysis of a lead-doped oxide film prepared by a focused ion beam (FIB) demonstrated that both Cr-rich and Ni-rich oxides were alternatively distributed within the outer layer, whereas the inner layer was porous and poorly protected, causing severe corrosion of the alloy and a thicker film was formed. A duplex film model was proposed for the effects discussion of lead on the oxidation mechanism.

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