Observations on the Dissolution Behavior Of Iron Whiskers

The dissolution behavior of iron whiskers has been studied in the solutions: 1N sulfuric acid + 0.2N potassium persulfate (K₂S₂O₈), a 4 percent solution of picric acid in alcohol, and a 2 percent solution of nitric acid in alcohol. Most whiskers were composed of a distinct shell or overgrowth surrounding the core. The shells ranged in thickness from less than one micron up to several microns. The thickness of the shell was a major factor in determining the size of the etch pits. Etch pits in the shell were usually smaller and better defined than pits in the whisker core. This variation in the shape of pits in different layers of the whisker, even though etched in the same solution, is attributed to a change in concentration of an internal poison.