On the problem of theoretical estimation of alloying additives effect on susceptibility of zirconium alloys to nodular corrosion

Abstract Several mechanisms of nodular corrosion are discussed in literature for Zr-based alloys. One of the mechanisms is attributed to instability of the uniform corrosion front with respect to transverse perturbations. According to this mechanism, a nonuniform field of mechanical stress is formed at the disturbed metal–oxide interface. It leads to redistribution of alloying elements in the vicinity of the corrosion front and concentration of additives in the metal becomes inhomogeneous. Depending on properties of the particular additive and its effect on local corrosion rate, the drift in the field of mechanical stress may lead to either enhancement or suppression of the arising perturbations. In the present paper, this approach for nodular corrosion understanding is further developed. An analytical solution for mechanical stresses in the metal–oxide system with undulated interface is reported. For undulations of small amplitude the solution is built in the frame of elastic theory. Results of analysis are applied to additives of Fe, Cr, Ni and Sn in Zircaloy-type alloys. Effects of both solutes and precipitates of these additives on susceptibility of alloys to nodular corrosion are considered.