1960 年 24 巻 8 号 p. 522-526
The etching process of polycrystalline zirconium by acid has been investigated into by means of an electron microscope, using the replica method. Mainly, aqueous solution of fluoric acid and, complementarily, “Gulbransen reagent” and conc. sulphuric acid have been used as etching reagents. Etch pits with density of 109/cm2 appear at first on a zirconium surface attacked by aqueous solution of fluoric acid. With increasing etching duration, they are transformed into semispherical small depressions, which are developed inwards and finally fused with each other. Thus, the etched surface is ultimately composed by coalescence of these developed depressions. It is concluded that the pits do not always correspond to dislocations. The etching process by “Gulbransen reagent” and by conc. sulphuric acid is almost the same as that by aqueous solution of fluoric acid.