Localized corrosion of zirconium and zircaloy-4 in iodine alcoholic solutions

The stress corrosion cracking (SCC) susceptibility of zirconium and one of its alloys, Zircaloy-4, was studied in 10 g/L iodine dissolved in various alcohols: methanol, ethanol, 1-propanol, 1-butanol and 1-pentanol. SCC was observed in all the systems studied and the crack propagation rate was found to vary depending on the size of the solvent molecule. When the molecular weight of the solvent molecule increased, the crack propagation rate decreased. Intergranular attack was also found in all the solutions tested, and the rate of intergranular corrosion also varied with the size of the solvent molecule. This behavior is attributed to a steric effect, which hinders the access of the corrosive species to the tip of the crack. The results found agree with the predictions of the surface mobility-SCC mechanism.