METHOD FOR REMOVING OXIDE FILM FROM SURFACE OF ZR AND HF AS WELL AS ITS ALLOY

摘要

PURPOSE:To remove thoroughly a titled film of various shapes without any problem in safety and the decrease in yield in an AC electrolytic treatment method in NH4F, by adding ammonium salt of such as citric acid or the like and specifying pH and current density. CONSTITUTION:Zr, Hf and an alloy thereof having an oxide film are subjected to Ac electrolysis in an aq. electrolytic soln. which contains 0.1-0.5mol concn. of NH4F and is adjusted to 5-6pH by adding =1 kinds among NH4, Na and K salts of a citric acid, oxalic acid, and tartaric acid thereto. The current density in this stage is set at 0.02-0.5A/cm2. Then the dissolving rate of the base metal itself is suppressed extremely low, and the dissolving rate in the boundary layer part of the base metal and the oxide film layer is increased, whereby the oxide film is stripped from the base metal. If slight NH4NO3 is allowed to exist in the above-described aq. electrolytic soln., the power for stripping the oxide film particularly in the case of the Sn-contg. alloy is further improved.