HYDROGEN DIFFUSIVITY AND SOLUBILITY IN CRYSTALLINE AND AMORPHOUS-ALLOYS

The hydrogen permeation behaviour of iron-and nickel-based amorphous a lloys was characterized using electrochemical methodology and compared with the properties of crystalline metals and alloys. The materials s tudied were amorphous Fe40Ni38Mo4B18, Fe74Ni4Mo3B17, Fe78B13Si9 and Ni 81P19, as well as a crystalline low-carbon steel, pure nickel and pure palladium. The double potentiostatic electrochemical hydrogen permeat ion tests were performed at 40 degrees C using a 0.1 N NaOH solution a s electrolyte. It was found that the hydrogen diffusivity in the iron- based amorphous alloys is a few orders of magnitude lower than in carb on steel and iron, while a much smaller difference exists between Ni81 P19 and pure nickel. Furthermore, the amorphous alloys showed a striki ngly greater capacity to dissolve hydrogen in solid solution compared with their crystalline counterparts. In some cases, their apparent hyd rogen solubility was even greater than that for the liquid metal of th e main element present in their chemical composition.