Controlled composition Zircaloy-2 uniform corrosion resistance

This paper reports on the influence of chemical composition and manufacturing variables on the nodular corrosion resistance (determined by 500 degrees C non-refreshed steam autoclave testing) of controlled composition Zircaloy-2 that was reported previously. The present study extends the previous work to include uniform corrosion, which is of interest for cladding tubes and spacer strips. Controlled composition Zircaloy-2 is defined where nickel and iron are adjusted towards the upper ASTM composition limits and tin is adjusted towards the lower limit. To investigate the effects of tin, iron, chromium, and nickel on the uniform corrosion of Zircaloy-2, a special 5500-kg ingot was triple melted. The composition was intentionally varied within a controlled portion of the ASTM B 350 range along the ingot length. Specimens of the ingot with different compositions were hot worked and beta quenched at a common size. Strip specimens (0.7 mm thick) were fabricated using three process schedules spanning the annealing parameter ΣAi = Σti exp(- 80 000/RTi) range applicable to current production practice for either tubeshell or strip material. Corrosion weight gains were obtained from 360 and 420 degrees C static autoclave tests extending to over 500 days exposure