Round-Robin Tests to Develop a Standard Autoclave Testing Procedure for Zirconium Alloys

Section I, Subcommittee VIII of ASTM Committee G-1 on Corrosion of Metals conducted two interlaboratory tests, the first with Zircaloy-2, the second with 2.5Nb zirconium, to formulate standard autoclave test procedures for zirconium alloys. In Interlaboratory #1, each laboratory used its own test procedure. The large scatter in data is attributed primarily to differences in autoclave start-up techniques, with minor contributions from variations in pickling time, and residual oxygen remaining in the autoclaves. Standard coupon preparation techniques were invoked for the 2.5Nb zirconium Interlaboratory #2; ASTM proposed standard G-2, 1967, was used for autoclave start-up. The good reproducibility from Interlaboratory #2 confirmed the acceptability of the proposed ASTM standard autoclave procedure. Decreased corrosion of annealed 2.5Nb zirconium with time is attributed to the monotectoid transformation of Nb enriched βZr to αZr plus βNb.